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Press and interference fits...Help!
Ive made 6 pairs of spacers...between a driven shaft (both ends) and a
bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? This is what Ive been machineing parts for... http://www.datinternational.ca/product.php?punits Im going to have to get the Clausing 15" lathe running..the Hardinge HLV-H...is way way too small for most of the work. I installed a Axelson 20x120 lathe in their shop...but they dont have 3ph yet..or anytime soon...sigh.... This one.... http://cgi.ebay.com/ws/eBayISAPI.dll...m=350318954988 Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
"Gunner Asch" wrote in message ... Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... This doesn't make sense. Are you measuring correctly? Is the inner race cracked? Or, I'm not seeing the issue, re-explain it. (I often cheat with some .001" brass foil.) |
Press and interference fits...Help!
On Tue, 10 Aug 2010 21:46:38 -0700, Gunner Asch
wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? I'd guess your problem is in measurement. An interference fit of ..002" does not slide on with a wee bump from a block of wood. Did you measure the bearing race ID or go with published specs? If you measured, how did you do it? ID's are tricky to measure accurately with telescoping gages or inside mikes and impossible with dial or digital calipers. Enco has a hell of a sale going on bore gages right now, about 30 bux which is about 1/3 usual price. I just got three sizes with the money I didn't spend on smokes the past couple of weeks. They're Chinese, but they look like they'll work very nicely. I see no reason not to trust them to a couple of tenths since the outside mikes I'll use to calibrate them are known to be good to a tenth. Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. They can be accurate to within a couple of tenths with enough practice but I don't trust them to better than a thou in my hands and that only after five measurements that agree. The Enco bore gages use consistent spring force and a DI so they don't depend on "feel". |
Press and interference fits...Help!
On Wed, 11 Aug 2010 01:57:58 -0400, "Buerste"
wrote: "Gunner Asch" wrote in message .. . Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... This doesn't make sense. Are you measuring correctly? Is the inner race cracked? Or, I'm not seeing the issue, re-explain it. (I often cheat with some .001" brass foil.) I know it doesnt make sense. And yes..Im measuring correctly and machining correctly. So what is the formula? I like the brass foil idea. Hell..I told them that Id give it a couple tiny shots with the TIG, so it would be removable years later when it needed to be serviced again...no dice. My 2 hour bill has turned into an unpaid 12 hours so far. Granted..Im learning lots of stuff...Id like to learn how to do it properly Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 01:09:45 -0500, Don Foreman
wrote: On Tue, 10 Aug 2010 21:46:38 -0700, Gunner Asch wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? I'd guess your problem is in measurement. An interference fit of .002" does not slide on with a wee bump from a block of wood. No kidding. Did you measure the bearing race ID or go with published specs? If you measured, how did you do it? ID's are tricky to measure accurately with telescoping gages or inside mikes and impossible with dial or digital calipers. Telescoping gages and mics. Its all I have. There are no published specs I could get easily. Enco has a hell of a sale going on bore gages right now, about 30 bux which is about 1/3 usual price. I just got three sizes with the money I didn't spend on smokes the past couple of weeks. They're Chinese, but they look like they'll work very nicely. I see no reason not to trust them to a couple of tenths since the outside mikes I'll use to calibrate them are known to be good to a tenth. Indeed. ID of the race was 2.667 based on the average of 10 measurements. Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. They can be accurate to within a couple of tenths with enough practice but I don't trust them to better than a thou in my hands and that only after five measurements that agree. The Enco bore gages use consistent spring force and a DI so they don't depend on "feel". How big will they go? Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
"Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 01:09:45 -0500, Don Foreman wrote: On Tue, 10 Aug 2010 21:46:38 -0700, Gunner Asch wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? I'd guess your problem is in measurement. An interference fit of .002" does not slide on with a wee bump from a block of wood. No kidding. Did you measure the bearing race ID or go with published specs? If you measured, how did you do it? ID's are tricky to measure accurately with telescoping gages or inside mikes and impossible with dial or digital calipers. Telescoping gages and mics. Its all I have. There are no published specs I could get easily. Enco has a hell of a sale going on bore gages right now, about 30 bux which is about 1/3 usual price. I just got three sizes with the money I didn't spend on smokes the past couple of weeks. They're Chinese, but they look like they'll work very nicely. I see no reason not to trust them to a couple of tenths since the outside mikes I'll use to calibrate them are known to be good to a tenth. Indeed. ID of the race was 2.667 based on the average of 10 measurements. Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. They can be accurate to within a couple of tenths with enough practice but I don't trust them to better than a thou in my hands and that only after five measurements that agree. The Enco bore gages use consistent spring force and a DI so they don't depend on "feel". How big will they go? Gunner The only good thing about this problem is that,if someone with your experience is having trouble, then it makes us amatures feel a little better when we get it wrong. If you can give me the bearing number, I might be able to find the specified diameter. |
Press and interference fits...Help!
"Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 01:57:58 -0400, "Buerste" wrote: "Gunner Asch" wrote in message . .. Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... This doesn't make sense. Are you measuring correctly? Is the inner race cracked? Or, I'm not seeing the issue, re-explain it. (I often cheat with some .001" brass foil.) I know it doesnt make sense. And yes..Im measuring correctly and machining correctly. So what is the formula? I like the brass foil idea. Hell..I told them that Id give it a couple tiny shots with the TIG, so it would be removable years later when it needed to be serviced again...no dice. My 2 hour bill has turned into an unpaid 12 hours so far. Granted..Im learning lots of stuff...Id like to learn how to do it properly Gunner Sorry dude, you're NOT measuring correctly. Telescoping gauges are very tricky and somewhat subjective. Turn a piece of scrap until you get the fit you want then turn your piece to those numbers. |
Press and interference fits...Help!
"Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 01:09:45 -0500, Don Foreman wrote: On Tue, 10 Aug 2010 21:46:38 -0700, Gunner Asch wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? I'd guess your problem is in measurement. An interference fit of .002" does not slide on with a wee bump from a block of wood. No kidding. Did you measure the bearing race ID or go with published specs? If you measured, how did you do it? ID's are tricky to measure accurately with telescoping gages or inside mikes and impossible with dial or digital calipers. Telescoping gages and mics. Its all I have. There are no published specs I could get easily. A cheap or worn telescoping gage can develop detents where you have locked it down before. When locked inside the bore, it will jump to the next smaller detent position. Test it by setting your outside micrometer a few thou larger than the shaft (i.e. the actual size of the ID). Put the telescoping gage between the micrometer anvils and lock it. Then turn the micrometer to see if the telescoping gage shrunk while locking. |
Press and interference fits...Help!
"Don Foreman" wrote in message ... snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. When you start using telescoping gauges as they should be used, you'll come to realize they are very precise measuring instruments. Harold |
Press and interference fits...Help!
On Wed, 11 Aug 2010 03:36:09 -0400, "Buerste"
wrote: "Gunner Asch" wrote in message .. . On Wed, 11 Aug 2010 01:57:58 -0400, "Buerste" wrote: "Gunner Asch" wrote in message ... Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... This doesn't make sense. Are you measuring correctly? Is the inner race cracked? Or, I'm not seeing the issue, re-explain it. (I often cheat with some .001" brass foil.) I know it doesnt make sense. And yes..Im measuring correctly and machining correctly. So what is the formula? I like the brass foil idea. Hell..I told them that Id give it a couple tiny shots with the TIG, so it would be removable years later when it needed to be serviced again...no dice. My 2 hour bill has turned into an unpaid 12 hours so far. Granted..Im learning lots of stuff...Id like to learn how to do it properly Gunner Sorry dude, you're NOT measuring correctly. Telescoping gauges are very tricky and somewhat subjective. Turn a piece of scrap until you get the fit you want then turn your piece to those numbers. Id have to press the piece of scrap and then press it on..and figure out how to get it back off, or out. Cringe.... Ive got a number of those Mity 3 fingered mics..but none that size range. Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 16:45:25 +1000, "Grumpy"
wrote: "Gunner Asch" wrote in message .. . On Wed, 11 Aug 2010 01:09:45 -0500, Don Foreman wrote: On Tue, 10 Aug 2010 21:46:38 -0700, Gunner Asch wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? I'd guess your problem is in measurement. An interference fit of .002" does not slide on with a wee bump from a block of wood. No kidding. Did you measure the bearing race ID or go with published specs? If you measured, how did you do it? ID's are tricky to measure accurately with telescoping gages or inside mikes and impossible with dial or digital calipers. Telescoping gages and mics. Its all I have. There are no published specs I could get easily. Enco has a hell of a sale going on bore gages right now, about 30 bux which is about 1/3 usual price. I just got three sizes with the money I didn't spend on smokes the past couple of weeks. They're Chinese, but they look like they'll work very nicely. I see no reason not to trust them to a couple of tenths since the outside mikes I'll use to calibrate them are known to be good to a tenth. Indeed. ID of the race was 2.667 based on the average of 10 measurements. Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. They can be accurate to within a couple of tenths with enough practice but I don't trust them to better than a thou in my hands and that only after five measurements that agree. The Enco bore gages use consistent spring force and a DI so they don't depend on "feel". How big will they go? Gunner The only good thing about this problem is that,if someone with your experience is having trouble, then it makes us amatures feel a little better when we get it wrong. If you can give me the bearing number, I might be able to find the specified diameter. They got tired of me ****ing around, delivering perfect and well machined spacers that were the wrong size, so they pulled a pair off a junk machine and hammered them in with a sledge hammer.....sigh. Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 00:52:00 -0700, "anorton"
wrote: "Gunner Asch" wrote in message .. . On Wed, 11 Aug 2010 01:09:45 -0500, Don Foreman wrote: On Tue, 10 Aug 2010 21:46:38 -0700, Gunner Asch wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? I'd guess your problem is in measurement. An interference fit of .002" does not slide on with a wee bump from a block of wood. No kidding. Did you measure the bearing race ID or go with published specs? If you measured, how did you do it? ID's are tricky to measure accurately with telescoping gages or inside mikes and impossible with dial or digital calipers. Telescoping gages and mics. Its all I have. There are no published specs I could get easily. A cheap or worn telescoping gage can develop detents where you have locked it down before. When locked inside the bore, it will jump to the next smaller detent position. Test it by setting your outside micrometer a few thou larger than the shaft (i.e. the actual size of the ID). Put the telescoping gage between the micrometer anvils and lock it. Then turn the micrometer to see if the telescoping gage shrunk while locking. Thanks. But Ive got several sets of telescoping gages. One for the normal run and a brand new Starret that I only use on Special Stuff...and thats what I used. Next time..Ill make the damned things ..005 undersize and let em beat em on. And the sad thing was..there really wasnt any need to press fit the damned things. They would have worked just fine as I delivered them. Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 08:17:02 GMT, "Harold & Susan Vordos"
wrote: "Don Foreman" wrote in message .. . snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. When you start using telescoping gauges as they should be used, you'll come to realize they are very precise measuring instruments. Harold Pretty much what Ive found and up until this project..Ive never had any problems using the damned things. And Ive machined a thing or two to far less than 2 grand. Afterall..I got the IDs perfectly each and every time. 12 of the damned things. Its been the simple as **** ODs that were giving me the ass. Shrug...so no one has any hints on how to calculate what a good intereference fit is? A double interference? Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 08:14:24 -0400, "Rick" wrote:
"Gunner Asch" wrote in message .. . On Wed, 11 Aug 2010 00:52:00 -0700, "anorton" wrote: "Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 01:09:45 -0500, Don Foreman wrote: On Tue, 10 Aug 2010 21:46:38 -0700, Gunner Asch wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? I'd guess your problem is in measurement. An interference fit of .002" does not slide on with a wee bump from a block of wood. No kidding. Did you measure the bearing race ID or go with published specs? If you measured, how did you do it? ID's are tricky to measure accurately with telescoping gages or inside mikes and impossible with dial or digital calipers. Telescoping gages and mics. Its all I have. There are no published specs I could get easily. A cheap or worn telescoping gage can develop detents where you have locked it down before. When locked inside the bore, it will jump to the next smaller detent position. Test it by setting your outside micrometer a few thou larger than the shaft (i.e. the actual size of the ID). Put the telescoping gage between the micrometer anvils and lock it. Then turn the micrometer to see if the telescoping gage shrunk while locking. Thanks. But Ive got several sets of telescoping gages. One for the normal run and a brand new Starret that I only use on Special Stuff...and thats what I used. Next time..Ill make the damned things .005 undersize and let em beat em on. And the sad thing was..there really wasnt any need to press fit the damned things. They would have worked just fine as I delivered them. Gunner Curious myself..what is the thickness of the spacer? Material? Tubular, out of steel (first batch was marked 12L14..but it was not! That **** was hard hard hard!! and the first set of spacers Cracked when pressed on the shafts. And they were .002 under. Hard enough to burn out a decent carbide insert at 500 rmp in about 10 seconds. I tossed the entire bar into the scrap bin. All 75 lbs of it. wall thickness was about (from memory) about .235 OD was about 2.166, best as I can recall at 6:38 in the morning They were spacers that were pressed on to the ends of a double herringbone drive gear, with a 13" x 3" herringbone gear near one end. Then a 8" bearing was put on each end to support the drive gear(s), which then drove a second larger herringbone drive gear, which actually turned the drive shaft that spun the counterweights and lifted the pumping unit "arm". Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 07:15:35 -0500, Karl Townsend
wrote: Shrug...so no one has any hints on how to calculate what a good intereference fit is? A double interference? Gunner Have you got machinery handbook. great section on fits. If you don't I'll look it up. .002 is about right. Karl Thats what I figured. Doesnt this depend though..on the diameter of the item? Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 08:25:12 -0400, "Rick" wrote:
"Gunner Asch" wrote in message .. . On Wed, 11 Aug 2010 08:17:02 GMT, "Harold & Susan Vordos" wrote: "Don Foreman" wrote in message ... snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. When you start using telescoping gauges as they should be used, you'll come to realize they are very precise measuring instruments. Harold Pretty much what Ive found and up until this project..Ive never had any problems using the damned things. And Ive machined a thing or two to far less than 2 grand. Afterall..I got the IDs perfectly each and every time. 12 of the damned things. Its been the simple as **** ODs that were giving me the ass. Shrug...so no one has any hints on how to calculate what a good intereference fit is? A double interference? Gunner I think the fact it's a double press is being overlooked. Were/are you able to measure the OD after it was pressed on the shaft? No..I wasnt. WHich is where I think things turned to ****. "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 07:27:01 -0500, Sunworshipper wrote:
On Wed, 11 Aug 2010 02:00:29 -0700, Gunner Asch wrote: On Wed, 11 Aug 2010 08:17:02 GMT, "Harold & Susan Vordos" wrote: "Don Foreman" wrote in message ... snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. When you start using telescoping gauges as they should be used, you'll come to realize they are very precise measuring instruments. Harold Pretty much what Ive found and up until this project..Ive never had any problems using the damned things. And Ive machined a thing or two to far less than 2 grand. Afterall..I got the IDs perfectly each and every time. 12 of the damned things. Its been the simple as **** ODs that were giving me the ass. Shrug...so no one has any hints on how to calculate what a good intereference fit is? A double interference? Gunner The main thing on my mind is the heat of machining, didn't see anyone mention it. Yeah yeah, I'm sure you know all too well about that, but I've met you, you seem to be one of those rush type of people when your working. Im more than aware that stuff Swells up when hot G..and let things cool down before measuring things like ID and whatnot. The feel is the most important, got to plant your head in the Zen zone. Got me, I'd have to be there. I have real trouble visualizing the written word to objects for some reason. SW "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
"Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 08:25:12 -0400, "Rick" wrote: "Gunner Asch" wrote in message . .. On Wed, 11 Aug 2010 08:17:02 GMT, "Harold & Susan Vordos" wrote: "Don Foreman" wrote in message m... snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. When you start using telescoping gauges as they should be used, you'll come to realize they are very precise measuring instruments. Harold Pretty much what Ive found and up until this project..Ive never had any problems using the damned things. And Ive machined a thing or two to far less than 2 grand. Afterall..I got the IDs perfectly each and every time. 12 of the damned things. Its been the simple as **** ODs that were giving me the ass. Shrug...so no one has any hints on how to calculate what a good intereference fit is? A double interference? Gunner I think the fact it's a double press is being overlooked. Were/are you able to measure the OD after it was pressed on the shaft? No..I wasnt. WHich is where I think things turned to ****. In case you missed the link....hoop stress http://www.eng-tips.com/viewthread.c...=184053&page=1 |
Press and interference fits...Help!
Gunner Asch wrote:
On Wed, 11 Aug 2010 03:36:09 -0400, "Buerste" wrote: "Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 01:57:58 -0400, "Buerste" wrote: "Gunner Asch" wrote in message ... Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... This doesn't make sense. Are you measuring correctly? Is the inner race cracked? Or, I'm not seeing the issue, re-explain it. (I often cheat with some .001" brass foil.) I know it doesnt make sense. And yes..Im measuring correctly and machining correctly. So what is the formula? I like the brass foil idea. Hell..I told them that Id give it a couple tiny shots with the TIG, so it would be removable years later when it needed to be serviced again...no dice. My 2 hour bill has turned into an unpaid 12 hours so far. Granted..Im learning lots of stuff...Id like to learn how to do it properly Gunner Sorry dude, you're NOT measuring correctly. Telescoping gauges are very tricky and somewhat subjective. Turn a piece of scrap until you get the fit you want then turn your piece to those numbers. Id have to press the piece of scrap and then press it on..and figure out how to get it back off, or out. Cringe.... Ive got a number of those Mity 3 fingered mics..but none that size range. Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 You probably know it already, if a bearing is a smidgen loosein its housing, unless the mission is critical an old dodge is to put say 30 center punch detents all around inside the housing. This raises a little ridge on each punch mark, and collectively will make the bearing surprisingly tight to press in, especially if you use one of those locktite glues to infill as well. |
Press and interference fits...Help!
On Wed, 11 Aug 2010 10:29:06 -0400, "Rick" wrote:
"Gunner Asch" wrote in message .. . On Wed, 11 Aug 2010 08:25:12 -0400, "Rick" wrote: "Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 08:17:02 GMT, "Harold & Susan Vordos" wrote: "Don Foreman" wrote in message om... snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. When you start using telescoping gauges as they should be used, you'll come to realize they are very precise measuring instruments. Harold Pretty much what Ive found and up until this project..Ive never had any problems using the damned things. And Ive machined a thing or two to far less than 2 grand. Afterall..I got the IDs perfectly each and every time. 12 of the damned things. Its been the simple as **** ODs that were giving me the ass. Shrug...so no one has any hints on how to calculate what a good intereference fit is? A double interference? Gunner I think the fact it's a double press is being overlooked. Were/are you able to measure the OD after it was pressed on the shaft? No..I wasnt. WHich is where I think things turned to ****. In case you missed the link....hoop stress http://www.eng-tips.com/viewthread.c...=184053&page=1 I got the link after posting. Sometimes things come in out of order. I cant use a split bushing, unfortunately, but Ill definately check out the calcs for hoop stress.... Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 15:33:13 +0100, Ted Frater
wrote: Gunner Asch wrote: On Wed, 11 Aug 2010 03:36:09 -0400, "Buerste" wrote: "Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 01:57:58 -0400, "Buerste" wrote: "Gunner Asch" wrote in message ... Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... This doesn't make sense. Are you measuring correctly? Is the inner race cracked? Or, I'm not seeing the issue, re-explain it. (I often cheat with some .001" brass foil.) I know it doesnt make sense. And yes..Im measuring correctly and machining correctly. So what is the formula? I like the brass foil idea. Hell..I told them that Id give it a couple tiny shots with the TIG, so it would be removable years later when it needed to be serviced again...no dice. My 2 hour bill has turned into an unpaid 12 hours so far. Granted..Im learning lots of stuff...Id like to learn how to do it properly Gunner Sorry dude, you're NOT measuring correctly. Telescoping gauges are very tricky and somewhat subjective. Turn a piece of scrap until you get the fit you want then turn your piece to those numbers. Id have to press the piece of scrap and then press it on..and figure out how to get it back off, or out. Cringe.... Ive got a number of those Mity 3 fingered mics..but none that size range. Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 You probably know it already, if a bearing is a smidgen loosein its housing, unless the mission is critical an old dodge is to put say 30 center punch detents all around inside the housing. This raises a little ridge on each punch mark, and collectively will make the bearing surprisingly tight to press in, especially if you use one of those locktite glues to infill as well. Indeed. that was my first suggestion. The guy who tasked me with this indicated that they put a 1 yr warranty on the work..and didnt want it to move. I blinked..advised him it wouldnt move..and he refused nonetheless. So..I had to get it right..which evidently Im unable to do. Blush! Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
"Gunner Asch" wrote in message ... On Wed, 11 Aug 2010 10:29:06 -0400, "Rick" wrote: "Gunner Asch" wrote in message . .. On Wed, 11 Aug 2010 08:25:12 -0400, "Rick" wrote: "Gunner Asch" wrote in message m... On Wed, 11 Aug 2010 08:17:02 GMT, "Harold & Susan Vordos" wrote: "Don Foreman" wrote in message news:tde4665vbk633t429ror3nojhl8flef9n3@4ax. com... snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. When you start using telescoping gauges as they should be used, you'll come to realize they are very precise measuring instruments. Harold Pretty much what Ive found and up until this project..Ive never had any problems using the damned things. And Ive machined a thing or two to far less than 2 grand. Afterall..I got the IDs perfectly each and every time. 12 of the damned things. Its been the simple as **** ODs that were giving me the ass. Shrug...so no one has any hints on how to calculate what a good intereference fit is? A double interference? Gunner I think the fact it's a double press is being overlooked. Were/are you able to measure the OD after it was pressed on the shaft? No..I wasnt. WHich is where I think things turned to ****. In case you missed the link....hoop stress http://www.eng-tips.com/viewthread.c...=184053&page=1 I got the link after posting. Sometimes things come in out of order. I cant use a split bushing, unfortunately, but Ill definately check out the calcs for hoop stress.... Gunner There's a comment on using "constant volume" to calculate the diameter changes from press fits. I didn't do them based on your numbers, but a thou here and there..well, you know... |
Press and interference fits...Help!
"Gunner Asch" wrote in message ... Id have to press the piece of scrap and then press it on..and figure out how to get it back off, or out. Cringe.... Ive got a number of those Mity 3 fingered mics..but none that size range. Gunner Only turn a stub a couple of inches long. press it through. You only need new numbers from it. |
Press and interference fits...Help!
Gunner Asch wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? You know that the ODs you have been turning are round, but are you sure the matching ID you have been measuring is round? have you measured it in several different orientations to check this? Just a thought... |
Press and interference fits...Help!
On Wed, 11 Aug 2010 10:07:08 -0500, "Pete C."
wrote: Gunner Asch wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? You know that the ODs you have been turning are round, but are you sure the matching ID you have been measuring is round? have you measured it in several different orientations to check this? Just a thought... Yes...chuckle..that did come to me and I did check em. Simliar to within a tenth in all directions. Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
Hnadbook clip. lot more there
Allowance for Forced Fits.—The allowance per inch of diameter usually ranges from 0.001 inch to 0.0025 inch, 0.0015 being a fair average. Ordinarily the allowance per inch decreases as the diameter increases; thus the total allowance for a diameter of 2 inches might be 0.004 inch, whereas for a diameter of 8 inches the total allowance might not be over 0.009 or 0.010 inch. The parts to be assembled by forced fits are usually made cylindrical, although sometimes they are slightly tapered. The advantages of the taper form are that the possibility of abrasion of the fitted surfaces is reduced; that less pressure is required in assembling; and that the parts are more readily separated when renewal is required. On the other hand, the taper fit is less reliable, because if it loosens, the entire fit is free with but little axial movement. Some lubricant, such as white lead and lard oil mixed to the consistency of paint, should be applied to the pin and bore before assembling, to reduce the tendency toward abrasion. Pressure for Forced Fits.—The pressure required for assembling cylindrical parts depends not only upon the allowance for the fit, but also upon the area of the fitted surfaces, the pressure increasing in proportion to the distance that the inner member is forced in. The approximate ultimate pressure in tons can be determined by the use of the following formula in conjunction with the accompanying table of “Pressure Factors.” Assuming that A = area of surface in contact in “fit”; a = total allowance in inches; P = ultimate pressure required, in tons; F = pressure factor based upon assumption that the diameter of the hub is twice the diameter of the bore, that the shaft is of machine steel, and that the hub is of cast iron: |
Press and interference fits...Help!
On Wed, 11 Aug 2010 10:48:11 -0500, Karl Townsend
wrote: Hnadbook clip. lot more there Allowance for Forced Fits.—The allowance per inch of diameter usually ranges from 0.001 inch to 0.0025 inch, 0.0015 being a fair average. So I could have gone 3-5 inches rather than 2. I should have, damnit!! "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Tue, 10 Aug 2010 23:37:23 -0700, Gunner Asch
wrote: Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. They can be accurate to within a couple of tenths with enough practice but I don't trust them to better than a thou in my hands and that only after five measurements that agree. The Enco bore gages use consistent spring force and a DI so they don't depend on "feel". How big will they go? The biggest one that's on sale has a range of 2" to 6". |
Press and interference fits...Help!
On Wed, 11 Aug 2010 01:54:42 -0700, Gunner Asch
wrote: Indeed. ID of the race was 2.667 based on the average of 10 measurements. With telescoping gages, the "right" reading is probably the largest of several similar readings, not the average. It's easy to screw them up right at the instant of locking them before withdrawal. It's also easy to have them slip when miking them. |
Press and interference fits...Help!
On Wed, 11 Aug 2010 08:17:02 GMT, "Harold & Susan Vordos"
wrote: "Don Foreman" wrote in message .. . snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Exactly. So there are two "feels" involved that must be identical. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. And you've been a professional machinist for over 50 years. |
Press and interference fits...Help!
On 08/11/2010 01:54 AM, Gunner Asch wrote:
On Wed, 11 Aug 2010 16:45:25 +1000, wrote: "Gunner wrote in message ... On Wed, 11 Aug 2010 01:09:45 -0500, Don Foreman wrote: On Tue, 10 Aug 2010 21:46:38 -0700, Gunner wrote: Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? I'd guess your problem is in measurement. An interference fit of .002" does not slide on with a wee bump from a block of wood. No kidding. Did you measure the bearing race ID or go with published specs? If you measured, how did you do it? ID's are tricky to measure accurately with telescoping gages or inside mikes and impossible with dial or digital calipers. Telescoping gages and mics. Its all I have. There are no published specs I could get easily. Enco has a hell of a sale going on bore gages right now, about 30 bux which is about 1/3 usual price. I just got three sizes with the money I didn't spend on smokes the past couple of weeks. They're Chinese, but they look like they'll work very nicely. I see no reason not to trust them to a couple of tenths since the outside mikes I'll use to calibrate them are known to be good to a tenth. Indeed. ID of the race was 2.667 based on the average of 10 measurements. Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. They can be accurate to within a couple of tenths with enough practice but I don't trust them to better than a thou in my hands and that only after five measurements that agree. The Enco bore gages use consistent spring force and a DI so they don't depend on "feel". How big will they go? Gunner The only good thing about this problem is that,if someone with your experience is having trouble, then it makes us amatures feel a little better when we get it wrong. If you can give me the bearing number, I might be able to find the specified diameter. They got tired of me ****ing around, delivering perfect and well machined spacers that were the wrong size, so they pulled a pair off a junk machine and hammered them in with a sledge hammer.....sigh. Dimples and Loctite would have been better! I was going to suggest that you just dick around a bit machining the spacers just a bit bigger and bigger until you got the fit you wanted -- but it's too late now. I suspect that just going .0005 or .001 bigger than what you're doing now would have achieved a nice* press fit. * Not a "light" or a "hard" press fit -- a "nice" press fit, as in "that's nice enough for now, declare victory and run like hell". -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
Press and interference fits...Help!
On 08/11/2010 12:36 AM, Buerste wrote:
"Gunner wrote in message ... On Wed, 11 Aug 2010 01:57:58 -0400, wrote: "Gunner wrote in message ... Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... This doesn't make sense. Are you measuring correctly? Is the inner race cracked? Or, I'm not seeing the issue, re-explain it. (I often cheat with some .001" brass foil.) I know it doesnt make sense. And yes..Im measuring correctly and machining correctly. So what is the formula? I like the brass foil idea. Hell..I told them that Id give it a couple tiny shots with the TIG, so it would be removable years later when it needed to be serviced again...no dice. My 2 hour bill has turned into an unpaid 12 hours so far. Granted..Im learning lots of stuff...Id like to learn how to do it properly Gunner Sorry dude, you're NOT measuring correctly. Telescoping gauges are very tricky and somewhat subjective. Turn a piece of scrap until you get the fit you want then turn your piece to those numbers. Is that the pro machinists advice to pro machinists, or the pro machinists advice to pikers? It's what I do -- that, or I leave a bit of extra length on the end of the piece I'm turning, use that to establish the fit, then once I find it I turn that diameter all the way down, and trim off the excess length. This works for everything from a running fit to a light press fit (if the piece I'm fitting to isn't bell mouthed, in which case the fit turns into an "oh ****" press fit). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
Press and interference fits...Help!
On Wed, 11 Aug 2010 11:34:54 -0500, Don Foreman
wrote: On Tue, 10 Aug 2010 23:37:23 -0700, Gunner Asch wrote: Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. They can be accurate to within a couple of tenths with enough practice but I don't trust them to better than a thou in my hands and that only after five measurements that agree. The Enco bore gages use consistent spring force and a DI so they don't depend on "feel". How big will they go? The biggest one that's on sale has a range of 2" to 6". That would work just hunky for me Now if I can come up with some bucks...... "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On Wed, 11 Aug 2010 11:38:49 -0500, Don Foreman
wrote: On Wed, 11 Aug 2010 01:54:42 -0700, Gunner Asch wrote: Indeed. ID of the race was 2.667 based on the average of 10 measurements. With telescoping gages, the "right" reading is probably the largest of several similar readings, not the average. Yes..which makes doing an interference fit really problematical. Cause it should be the smallest reading one should be going for. It's easy to screw them up right at the instant of locking them before withdrawal. It's also easy to have them slip when miking them. Ayup. While Im nowhere qualified to be a machinist..its not exactly my first rodeo..and it kicked my ass well and proper. And its ****ing me off that I couldnt get it right. It was an interesting learning experience...indeed. Slapped the smug right the **** out of me. Gunner "A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9 |
Press and interference fits...Help!
On 08/11/2010 09:38 AM, Don Foreman wrote:
On Wed, 11 Aug 2010 01:54:42 -0700, Gunner wrote: Indeed. ID of the race was 2.667 based on the average of 10 measurements. With telescoping gages, the "right" reading is probably the largest of several similar readings, not the average. It's easy to screw them up right at the instant of locking them before withdrawal. It's also easy to have them slip when miking them. I stick the gauge into the hole, wiggle it around, tighten it, then wiggle it again -- if it doesn't feel right after I tighten it, I loosen it and try again. Not, mind you, that I resemble an experienced machinist in any way shape or form. Nor do I trust my ability to use a telescoping gauge to within less than .001 or .002. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
Press and interference fits...Help!
On Aug 10, 9:46*pm, Gunner Asch wrote:
Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. Well, remachining and shimming and additive welding are already mentioned. No one else said it, so here's my two cents worth: knurl |
Press and interference fits...Help!
On Wed, 11 Aug 2010 07:10:28 -0700, Gunner Asch
wrote: On Wed, 11 Aug 2010 07:27:01 -0500, Sunworshipper wrote: On Wed, 11 Aug 2010 02:00:29 -0700, Gunner Asch wrote: On Wed, 11 Aug 2010 08:17:02 GMT, "Harold & Susan Vordos" wrote: "Don Foreman" wrote in message m... snip--- Telescoping gages depend strongly on consistent "feel" and even good ones (Starrett) are easy to upset when locking to withdraw. [/quote] That's because you're not using them correctly. Rarely will you find *anyone* that will suggest you not lock after taking size, nor will you find many that say to go in the hole a second time before taking the measurement with your micrometer. They, unfortunately, are the ones that can't use them worth a damn, because they buy in to the BS that that's how it should be done. Well, it shouldn't. The lock should be set for a light drag feel, and the fit should be ascertained by going back in the hole a second time. If the gauge falls through the hole, you know the reading is bogus. If you can duplicate the feel, you know you have found center. You must then be able to transfer the same feel to the micrometer, otherwise you aren't reading the hole correctly. Anyone that tells you to measure several times and take an average of the reading can't use them, and likely never will, with success. That simply is not the way they should be used. I can use telescoping gauges and work to .0002" tolerance with reliability. Done it since I got started in the shop back in '57, often with a dial bore to verify my measurements. Most guys that can use them properly have the same success. I'm not "special"---I just use them correctly. When you start using telescoping gauges as they should be used, you'll come to realize they are very precise measuring instruments. Harold Pretty much what Ive found and up until this project..Ive never had any problems using the damned things. And Ive machined a thing or two to far less than 2 grand. Afterall..I got the IDs perfectly each and every time. 12 of the damned things. Its been the simple as **** ODs that were giving me the ass. Shrug...so no one has any hints on how to calculate what a good intereference fit is? A double interference? Gunner The main thing on my mind is the heat of machining, didn't see anyone mention it. Yeah yeah, I'm sure you know all too well about that, but I've met you, you seem to be one of those rush type of people when your working. Im more than aware that stuff Swells up when hot G..and let things cool down before measuring things like ID and whatnot. Angle of the dangle is proportionate to the heat ... Looks like ya got the answer, just 1.5 more. I'd love to have one of those red books just to read. I've only seen about 4 for a grand total of five minutes. And next on my wish list is a pointed diamond dresser. See I told ya, just a bit warm for 120F outside plus your 2 thou. They should have brought you one to copy if they wanted more than two! The feel is the most important, got to plant your head in the Zen zone. Got me, I'd have to be there. I have real trouble visualizing the written word to objects for some reason. SW |
Press and interference fits...Help!
Allowance for Forced Fits.—The allowance per inch of diameter usually ranges from 0.001 inch to 0.0025 inch, 0.0015 being a fair average. So I could have gone 3-5 inches rather than 2. I should have, damnit!! The one good thing about learning from the school of hard knocks... You don't forget the lesson. Karl |
Press and interference fits...Help!
Gunner Asch wrote:
Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... Anyone got any ideas/help/calcs that would fill in this blank space in my knowlege? Damn Gunner, you did have a bad day. My technique with telescoping gages is to insert them into a clean bore at an angle so they are longer than the ID. Lock the set screw, then wipe once. Carefully, with a light hand measure your telescoping gage, write down the number. Repeat. Really worried, repeat again. If you are not getting the same measurement with in the tolerance of what will be good try to figure out what you are doing wrong. You don't average, the largest measurement should be the correct one. I have a set of old Starrett telescoping gages at work. These are the type where only one side telescopes. I also have a newer set of gages where both sides telescope at home. I can honestly say, I'd rather have only one side telescope. I haven't shot myself in the foot with the new ones yet but I just don't like how they feel. On the fit. I tend to use 0.001" per inch but I know there are all sorts of fits and some are a bit more aggressive. Sorry if my post this morning shows up and turns this into a double post. I read enough to see they gave up on you. Oh well, that can happen. You need to try to fab up something similar to test your technique. This is fairly easy chit so I understand why you are asking for help. Heck if it is something that is weird enough, maybe you can save some face with them if you can explain wtf happened and they care. I have notchy bearings in my cross feed that I got to get fixed. I've blown a couple dimensions when .020" more became something else. I got to fix it soon. Got to work this weekend but I have the following one off. I'll put that on my to do list. -- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller |
Press and interference fits...Help!
"Tim Wescott" wrote in message ... On 08/11/2010 12:36 AM, Buerste wrote: "Gunner wrote in message ... On Wed, 11 Aug 2010 01:57:58 -0400, wrote: "Gunner wrote in message ... Ive made 6 pairs of spacers...between a driven shaft (both ends) and a bearing race and each and every time, Ive gotten the OD wrong. Each and every time..tap on the bearing race..and the ******* slides on. How the hell does one calculate such a thingy? This was off a pumping unit gearbox..and the people are starting to look at me like im an utter bumpkin...which it looks like I am...sigh. The ID was to have a .002" interference fit..and I accomplished this with no issues. I machined the OD to be .003 larger than the ID of the bearing race....and once the bearing race was tapped a couple times..the damned thing slid on with a tad bit more than hand pressure. Easy with a small block of wood. Blink blink.... This doesn't make sense. Are you measuring correctly? Is the inner race cracked? Or, I'm not seeing the issue, re-explain it. (I often cheat with some .001" brass foil.) I know it doesnt make sense. And yes..Im measuring correctly and machining correctly. So what is the formula? I like the brass foil idea. Hell..I told them that Id give it a couple tiny shots with the TIG, so it would be removable years later when it needed to be serviced again...no dice. My 2 hour bill has turned into an unpaid 12 hours so far. Granted..Im learning lots of stuff...Id like to learn how to do it properly Gunner Sorry dude, you're NOT measuring correctly. Telescoping gauges are very tricky and somewhat subjective. Turn a piece of scrap until you get the fit you want then turn your piece to those numbers. Is that the pro machinists advice to pro machinists, or the pro machinists advice to pikers? It's what I do -- that, or I leave a bit of extra length on the end of the piece I'm turning, use that to establish the fit, then once I find it I turn that diameter all the way down, and trim off the excess length. This works for everything from a running fit to a light press fit (if the piece I'm fitting to isn't bell mouthed, in which case the fit turns into an "oh ****" press fit). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html All the universe is a kludge! |
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