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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Change gear pressure angle
I have a Jet 1024 lathe with a QC gear box. The box has a broken gear
that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. |
#2
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Change gear pressure angle
On 21/01/17 18:53, Bob Engelhardt wrote:
I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. There are some programs or javascripts on the net which will generate gear profiles such as http://woodgears.ca/gear_cutting/template.html and others so maybe try a few and print off the result to compare with. Have you considered it may be a module gear size rather than DP. |
#3
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Change gear pressure angle
Bob Engelhardt wrote:
I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. AFAIK the 2 most common PA's are 20° and 14.5° . My Logan is all 14.5 ° .... -- Snag |
#4
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Change gear pressure angle
On Sat, 21 Jan 2017 13:53:29 -0500, Bob Engelhardt
wrote: I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. I assume you tried Jet already to see if a new gear is available and found out it is not. Since you are only making one gear you could grind a fly cutter to fit the existing gear. I have done this and it works well if only one gear is being made. Do you have any radius gauges? It may be that one will fit your gear teeth exaclty and if so you can use it as a gauge to grind a cutter. I know, the teeth have an involute form but only the beginning of the curve is used and it is so close to a true circle that a true circle shape is within the manufacturing toleranceof the original gear. As to the picture shown all the teeth of a particular DP are the same size so the gear diameter shouldn't matter, you just need to see if your tooth matches the shape of a sample tooth. You may be able to determine the pressure angle by tracing your gear teeth carefully on a piece of paper. Now, find the center of the tracing as close as you can and use this with a compass to draw a circle that is midway between the O.D. of the gear and the bottom of the space between the teeth, and another circle that is the same diameter as the bottom of the space between the teeth. Next, draw a line the bisects a tooth and pases through the center of the gear tracing. Where this line intersects the larger of the circles you drew make a point. From this point draw a line that is tangent to the smaller of the two circles you drew. Make another point at the tangent point. Finally, draw a line from this tangent point through the center. The angle between the two lines you drew that pass through the center of the tracing is the pressure angle. You should get an angle that is close to either 14.5 degrees or 20 degrees if everything is drawn right and the gear is made to one of the two most common pressure angles. It will be off a little because the smaller circle is a little smaller than the base circle where the pressure angle is measured from but I don't think it will make much of a difference, especially since you are working from a tracing. Eric |
#5
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Change gear pressure angle
On Sat, 21 Jan 2017 13:53:29 -0500, Bob Engelhardt
wrote: I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. What's the biggest gear in the box? The greater the number of teeth, the closer the tooth form gets to the trapezoidal shape of a rack tooth. For a rack, the pressure angle is equal to half the included angle of the tooth profile. If there isn't a gear with enough teeth to give you confidence in that method, you can measure the gear with pins, though this can get confusing if you're dealing with a non-standard pitch or tooth form (for example, stub teeth). Machinerys HB has info on measuring over pins. http://www.zakgear.com/Over_Pins.html -- Ned Simmons |
#6
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Change gear pressure angle
On 1/21/2017 2:04 PM, David Billington wrote:
There are some programs or javascripts on the net which will generate gear profiles such as http://woodgears.ca/gear_cutting/template.html and others so maybe try a few and print off the result to compare with. ... Thanks - I tried that. It took about 6 attempts to get it printed at full size, but it did. The problem was resolution: these teeth are only 3mm deep and 5mm pitch, so trying to match profiles is really hard. It did look like 20 degree PA, though. Bob |
#7
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Change gear pressure angle
On Sat, 21 Jan 2017 18:28:32 -0500, Ned Simmons
wrote: On Sat, 21 Jan 2017 13:53:29 -0500, Bob Engelhardt wrote: I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. What's the biggest gear in the box? The greater the number of teeth, the closer the tooth form gets to the trapezoidal shape of a rack tooth. For a rack, the pressure angle is equal to half the included angle of the tooth profile. If there isn't a gear with enough teeth to give you confidence in that method, you can measure the gear with pins, though this can get confusing if you're dealing with a non-standard pitch or tooth form (for example, stub teeth). Machinerys HB has info on measuring over pins. http://www.zakgear.com/Over_Pins.html Forgot to mention: You can generate a rack by rolling your gear thru a lump of clay. Measure the teeth of the clay rack. -- Ned Simmons |
#8
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Change gear pressure angle
On 1/21/2017 3:06 PM, Terry Coombs wrote:
AFAIK the 2 most common PA's are 20° and 14.5° . My Logan is all 14.5 ° Oh, yeah - I forgot to mention that. The 2 Boston Gear profiles are 20 & 14-1/2 degrees. Old gears are most likely 14-1/2 & new ones 20, but I don't know if one made in 1980 in old or new. Bob |
#9
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Change gear pressure angle
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#10
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Change gear pressure angle
wrote in message
... On Sat, 21 Jan 2017 13:53:29 -0500, Bob Engelhardt wrote: I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. I assume you tried Jet already to see if a new gear is available and found out it is not. Since you are only making one gear you could grind a fly cutter to fit the existing gear. I have done this and it works well if only one gear is being made. .... Eric I cut two satisfactory (not perfect) gears with flycutter bits too. The job required a jig that guided the bit blank into centered alignment with the tooth space. Bluing didn't transfer or print well on the smooth hardened lathe bit so I held the bit and old gear up to the light to see the contact and marked the blank's top surface to show where to grind. Roughing out the tooth spaces first with a more efficient cutter helped a lot. The tooth spaces can be cut nearly to size before the bit has been ground to final fit so it will be freshly sharp for the finish cut. The grinding jig might serve as a gauge for depth of cut. -jsw |
#11
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Change gear pressure angle
On Sat, 21 Jan 2017 13:53:29 -0500, Bob Engelhardt
wrote: I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. Greetings Bob, I read my post after posting it and I though I would add a little clarification, or maybe obfuscation, your pick. So, the pitch circle is the point of contact of the meshed gear teeth. The base circle is the theoretical base of the gear tooth. Any pair of gears must have the same ratio between the base circle and pitch circle in order to work together. This ratio is usually expressed as an angle, the pressure angle, for simplicity. Gear teeth are cut a little below the base circle diameter a little bit for clearance. So if you use the method I described to find the pressure angle it may come out wrong because you will be drawing a line tangent to a diameter that is slightly smaller than the base circle diameter. This will have the effect of making the apparent pressure angle larger. Not much different but if I didn't point out my error somebody else would have, and I don't want to look any worse than I already do. I should also point out that gears close to the same size with the same pressure angle and pitch will have teeth that closely resemble each other. But gears with a large difference in diameter will have teeth with curves that look much different. For example a rack, which is a gear of infinite diameter, has teeth with straight sides, with the angle of the sides being at the pressure angle, whereas a pinion with only a few teeth that meshes perfectly with the rack will have markedly curved teeth. Eric |
#12
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Change gear pressure angle
On Sat, 21 Jan 2017 18:31:22 -0500, Ned Simmons
wrote: On Sat, 21 Jan 2017 18:28:32 -0500, Ned Simmons wrote: On Sat, 21 Jan 2017 13:53:29 -0500, Bob Engelhardt wrote: I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. What's the biggest gear in the box? The greater the number of teeth, the closer the tooth form gets to the trapezoidal shape of a rack tooth. For a rack, the pressure angle is equal to half the included angle of the tooth profile. If there isn't a gear with enough teeth to give you confidence in that method, you can measure the gear with pins, though this can get confusing if you're dealing with a non-standard pitch or tooth form (for example, stub teeth). Machinerys HB has info on measuring over pins. http://www.zakgear.com/Over_Pins.html Forgot to mention: You can generate a rack by rolling your gear thru a lump of clay. Measure the teeth of the clay rack. Greetings Ned, That's a great simple solution. Thanks for posting it. Eric |
#13
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Change gear pressure angle
"Ned Simmons" wrote in message
... On Sat, 21 Jan 2017 18:28:32 -0500, Ned Simmons wrote: Forgot to mention: You can generate a rack by rolling your gear thru a lump of clay. Measure the teeth of the clay rack. -- Ned Simmons Crafts stores sell polymer clay that hardens when heated to 130C in an oven or with a hot air gun. -jsw |
#14
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Change gear pressure angle
On 2017-01-21, Bob Engelhardt wrote:
On 1/21/2017 2:04 PM, David Billington wrote: There are some programs or javascripts on the net which will generate gear profiles such as http://woodgears.ca/gear_cutting/template.html and others so maybe try a few and print off the result to compare with. ... Thanks - I tried that. It took about 6 attempts to get it printed at full size, but it did. The problem was resolution: these teeth are only 3mm deep and 5mm pitch, so trying to match profiles is really hard. It did look like 20 degree PA, though. Hmmm ... Given that the lathe was from Taiwan (or maybe mainland China -- not sure at that date) are you *sure* that it is an involute gear which matches an Imperial DP? Look for "Module" gears to see what you can find which is close to it in the metric world. It does not really look like the usual involute profile -- of either DP. I'm not sure what the pressure angles are for Module gears -- or whether they even offer two common angles. If that is the case, I'm not sure where you would go to get gear cutters of the right size. Your two sample images are both labeled "16 DP", but I do not see a pressure angle label on either. I would guess that the one on the left is the 20 degree PA. Good Luck, DoN. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#15
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Change gear pressure angle
On 1/21/2017 6:28 PM, Ned Simmons wrote:
What's the biggest gear in the box? The greater the number of teeth, the closer the tooth form gets to the trapezoidal shape of a rack tooth. For a rack, the pressure angle is equal to half the included angle of the tooth profile. Oh - good idea! I thought there was a much larger one, but I just checked and the broken one is the largest. 8-( If there isn't a gear with enough teeth to give you confidence in that method, you can measure the gear with pins, though this can get confusing if you're dealing with a non-standard pitch or tooth form (for example, stub teeth). Machinerys HB has info on measuring over pins. http://www.zakgear.com/Over_Pins.html OK, but I hope that I don't have to go there. About the rack having trapezoidal teeth: as a rack is "bent" to become a gear, the teeth center lines go from parallel to lines intersecting at the center (and the profile changes, too). Basically, the tooth-sides included angle is bigger by the angle between the center lines. So, if you could approximate where the trapezoidal side has morphed during the transformation, measure the included angle, subtract the tooth-to-tooth center line angle, and divide by 2 you would have the (approximate) pressure angle. It only has to be close enough to resolve between 14.5 and 20 degrees. http://imgur.com/a/DAT5P The angle between the white arrows is 51 degrees. It's a 36 tooth gear, so the tooth-tooth included angle is 10. (52 - 10) / 2 = 21 degrees. The red arrows are 38 degrees apart. (38 - 10) / 2 = 14 degrees. The zakgear page that you linked to has a drawing that suggests that the red lines would be the rack sides (the rack tooth is wider the top than the gear tooth). Thanks, Bob |
#16
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Change gear pressure angle
On 1/21/2017 6:31 PM, Ned Simmons wrote:
Forgot to mention: You can generate a rack by rolling your gear thru a lump of clay. Measure the teeth of the clay rack. I had read that on some forum and had tried it - the clay stuck to the gear and generally was very uncooperative. I thought I might try using epoxy putty in its almost-set state, but never got around to it. Also, the teeth are so small that I don't think that I could have measured the angles very well. |
#18
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Change gear pressure angle
On 1/21/2017 7:34 PM, DoN. Nichols wrote:
Hmmm ... Given that the lathe was from Taiwan (or maybe mainland China -- not sure at that date) are you *sure* that it is an involute gear which matches an Imperial DP? Look for "Module" gears to see what you can find which is close to it in the metric world. It does not really look like the usual involute profile -- of either DP. I'm not sure what the pressure angles are for Module gears -- or whether they even offer two common angles. ... I _think_ that are just 2 different measuring systems. That any gear can be described as having a certain DP or a certain module. There is a simple arithmetic relationship between them. The teeth are the same shape and that's what matters. |
#19
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Change gear pressure angle
On Sat, 21 Jan 2017 20:47:20 -0500, Bob Engelhardt
wrote: On 1/21/2017 6:31 PM, Ned Simmons wrote: Forgot to mention: You can generate a rack by rolling your gear thru a lump of clay. Measure the teeth of the clay rack. I had read that on some forum and had tried it - the clay stuck to the gear and generally was very uncooperative. I thought I might try using epoxy putty in its almost-set state, but never got around to it. Mold release spray is your friend. Also, the teeth are so small that I don't think that I could have measured the angles very well. Know anyone with an optical comparator? -- There is s no such thing as a hyphenated American who is a good American.* The only man who is a good American is the man who is an American and nothing else.* We are a nation, not a hodge-podge of foreign nationalities.* We are a people, and not a polyglot boarding house. --Theodore Roosevelt |
#20
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Change gear pressure angle
On 2017-01-22, Larry Jaques wrote:
On Sat, 21 Jan 2017 20:47:20 -0500, Bob Engelhardt wrote: [ ... ] Also, the teeth are so small that I don't think that I could have measured the angles very well. Know anyone with an optical comparator? Well ... I have one, but whether I am convenient is a different matter. I'm too close to Washington DC (Northern Va, and I'm not sure where the OP is located. Enjoy, DoN. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#21
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Change gear pressure angle
On Saturday, January 21, 2017 at 1:53:40 PM UTC-5, Bob Engelhardt wrote:
I have a Jet 1024 lathe with a QC gear box. The box has a broken gear that is really oddball in that its dimensions are inconsistent with published standards. Such that I cannot find a replacement in any of the usual places. Anyhow, I intend to make a new gear on my horizontal mill and will have to buy a gear cutter. That means that I need to know the pressure angle. I found a website with a procedure to do that, but it requires CAD and before I get into that, I'm trying here. (http://mikesworkshop.weebly.com/chan...ure-angle.html) Here is a photo of a couple of teeth on my gear and profiles of the same DP from Boston Gear. The Boston Gear profiles are a different diameter, so I can't compare by overlaying. I can't tell which angle is closest to mine. Anybody know gears well enough to tell? http://imgur.com/a/7O4O3 Thanks, Bob BTW - the lathe is from 1980 or so - if that helps. Just a few suggestions: 1) Make a friend at a precision machine shop that has an optical comparator.. You'l be able to look at the gear in excruciating detail and make all the measurements you need. 1a) Take a good, sharp close-up photo, making sure that the camera is square with the gear. Blow it up to several times actual size and take your measurements off the print. You can help this along by including a ruler in the photo for scale (or scribing some lines on the gear). 2) send the busted gear to Boston Gear and ask them to match it. Make sure to talk to someone first and to provide a return shipping label. |
#22
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Change gear pressure angle
On 1/23/2017 8:29 AM, rangerssuck wrote:
Just a few suggestions: 1) Make a friend at a precision machine shop that has an optical comparator. You'l be able to look at the gear in excruciating detail and make all the measurements you need. 1a) Take a good, sharp close-up photo, making sure that the camera is square with the gear. Blow it up to several times actual size and take your measurements off the print. You can help this along by including a ruler in the photo for scale (or scribing some lines on the gear). 2) send the busted gear to Boston Gear and ask them to match it. Make sure to talk to someone first and to provide a return shipping label. Thanks - I'll keep those in mind. |
#23
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Change gear pressure angle
I was looking at a picture of the lathe and the rack for the carriage
power feed caught my eye. That rack won't have the same DP as the broken gear, but it will _probably_ have the same pressure angle. I mean, what's the chance that a lathe maker would use different pressure angles in his gears? The point being, of course, that the rack teeth have straight sides and easily measured angles. |
#24
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Change gear pressure angle
On Mon, 23 Jan 2017 13:12:23 -0500
Bob Engelhardt wrote: On 1/23/2017 8:29 AM, rangerssuck wrote: Just a few suggestions: 1) Make a friend at a precision machine shop that has an optical comparator. You'l be able to look at the gear in excruciating detail and make all the measurements you need. 1a) Take a good, sharp close-up photo, making sure that the camera is square with the gear. Blow it up to several times actual size and take your measurements off the print. You can help this along by including a ruler in the photo for scale (or scribing some lines on the gear). 2) send the busted gear to Boston Gear and ask them to match it. Make sure to talk to someone first and to provide a return shipping label. Thanks - I'll keep those in mind. I hadn't seen it mentioned yet, but the book "Workshop Practice Series No 17 - Gears and Gear Cutting by Ivan Law" may help. If your lucky you might find it at the library. Otherwise its around $23: https://www.amazon.com/Gears-Gear-Cu...dp/0852429118/ It used to get mentioned here when your kind of question came up... -- Leon Fisk Grand Rapids MI/Zone 5b Remove no.spam for email |
#25
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Change gear pressure angle
Leon Fisk wrote:
On Mon, 23 Jan 2017 13:12:23 -0500 Bob Engelhardt wrote: On 1/23/2017 8:29 AM, rangerssuck wrote: Just a few suggestions: 1) Make a friend at a precision machine shop that has an optical comparator. You'l be able to look at the gear in excruciating detail and make all the measurements you need. 1a) Take a good, sharp close-up photo, making sure that the camera is square with the gear. Blow it up to several times actual size and take your measurements off the print. You can help this along by including a ruler in the photo for scale (or scribing some lines on the gear). 2) send the busted gear to Boston Gear and ask them to match it. Make sure to talk to someone first and to provide a return shipping label. Thanks - I'll keep those in mind. I hadn't seen it mentioned yet, but the book "Workshop Practice Series No 17 - Gears and Gear Cutting by Ivan Law" may help. If your lucky you might find it at the library. Otherwise its around $23: https://www.amazon.com/Gears-Gear-Cu...dp/0852429118/ It used to get mentioned here when your kind of question came up... I think I got my copy on Amazon for 17 bucks . Definitely a must-have for a beginner gear-cutter . BTW Bob , what dp is your gear ? I have a full set of 16 dp and a few 20 dp's . Ping me offline , my reply-to is good . -- Snag |
#26
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Change gear pressure angle
On Mon, 23 Jan 2017 14:21:11 -0400, Leon Fisk
wrote: On Mon, 23 Jan 2017 13:12:23 -0500 Bob Engelhardt wrote: On 1/23/2017 8:29 AM, rangerssuck wrote: Just a few suggestions: 1) Make a friend at a precision machine shop that has an optical comparator. You'l be able to look at the gear in excruciating detail and make all the measurements you need. 1a) Take a good, sharp close-up photo, making sure that the camera is square with the gear. Blow it up to several times actual size and take your measurements off the print. You can help this along by including a ruler in the photo for scale (or scribing some lines on the gear). 2) send the busted gear to Boston Gear and ask them to match it. Make sure to talk to someone first and to provide a return shipping label. Thanks - I'll keep those in mind. I hadn't seen it mentioned yet, but the book "Workshop Practice Series No 17 - Gears and Gear Cutting by Ivan Law" may help. If your lucky you might find it at the library. Otherwise its around $23: https://www.amazon.com/Gears-Gear-Cu...dp/0852429118/ It used to get mentioned here when your kind of question came up... Always check eBay, too. $14.73 delivered from the UK http://tinyurl.com/jx6jzbe -- There is s no such thing as a hyphenated American who is a good American.* The only man who is a good American is the man who is an American and nothing else.* We are a nation, not a hodge-podge of foreign nationalities.* We are a people, and not a polyglot boarding house. --Theodore Roosevelt |
#27
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Change gear pressure angle
On 2017-01-23, Bob Engelhardt wrote:
On 1/23/2017 8:29 AM, rangerssuck wrote: Just a few suggestions: [ ... ] 1a) Take a good, sharp close-up photo, making sure that the camera is square with the gear. Blow it up to several times actual size and take your measurements off the print. You can help this along by including a ruler in the photo for scale (or scribing some lines on the gear). If you have a scanner, put the gear flat in the middle of the scanner's plate, and scan it. That will probably be as good an image as you can get, and will make sure that the "camera" is square with the gear. Use the highest resolution (maximum DPI setting) on the scanner. You can possibl even use a sub-program in an image processing software package (e.g. GIMP or PhotoShop -- whichever you have) to get an outline of the gear -- better to work on importing that to a CAD program. Good Luck, DoN. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#28
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Change gear pressure angle
"Bob Engelhardt" wrote in message
news I was looking at a picture of the lathe and the rack for the carriage power feed caught my eye. That rack won't have the same DP as the broken gear, but it will _probably_ have the same pressure angle. I mean, what's the chance that a lathe maker would use different pressure angles in his gears? The point being, of course, that the rack teeth have straight sides and easily measured angles. Bearing Specialty in Nashua NH might be able to help you. Their phone is (603) 889-2222. -jsw |
#29
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Change gear pressure angle
"Bob Engelhardt" wrote in message
news On 1/23/2017 8:29 AM, rangerssuck wrote: Just a few suggestions: 1) Make a friend at a precision machine shop that has an optical comparator. You'l be able to look at the gear in excruciating detail and make all the measurements you need. 1a) Take a good, sharp close-up photo, making sure that the camera is square with the gear. Blow it up to several times actual size and take your measurements off the print. You can help this along by including a ruler in the photo for scale (or scribing some lines on the gear). 2) send the busted gear to Boston Gear and ask them to match it. Make sure to talk to someone first and to provide a return shipping label. Thanks - I'll keep those in mind. http://www.ereplacementparts.com/sea...et+change+gear |
#30
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Change gear pressure angle
On Tuesday, January 24, 2017 at 12:40:37 PM UTC-5, Jim Wilkins wrote:
"Bob Engelhardt" wrote in message news On 1/23/2017 8:29 AM, rangerssuck wrote: Just a few suggestions: 1) Make a friend at a precision machine shop that has an optical comparator. You'l be able to look at the gear in excruciating detail and make all the measurements you need. 1a) Take a good, sharp close-up photo, making sure that the camera is square with the gear. Blow it up to several times actual size and take your measurements off the print. You can help this along by including a ruler in the photo for scale (or scribing some lines on the gear). 2) send the busted gear to Boston Gear and ask them to match it. Make sure to talk to someone first and to provide a return shipping label. Thanks - I'll keep those in mind. http://www.ereplacementparts.com/sea...et+change+gear Nice! never heard of that place before, I'll file it away for the future. |
#31
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Change gear pressure angle
On 1/23/2017 1:21 PM, Leon Fisk wrote:
I hadn't seen it mentioned yet, but the book "Workshop Practice Series No 17 - Gears and Gear Cutting by Ivan Law" may help. ... I have the book. Good background & it even describes how to make a tool to make a cutter. I'm not good enough to do that. |
#32
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Change gear pressure angle
On 1/23/2017 11:54 PM, DoN. Nichols wrote:
If you have a scanner, put the gear flat in the middle of the scanner's plate, and scan it. That will probably be as good an image as you can get, and will make sure that the "camera" is square with the gear. Use the highest resolution (maximum DPI setting) on the scanner. ... That is a good idea! Why didn't I think of that? I did do a scan, at 1200dpi (not max) and got a great image: http://imgur.com/Zi8ZueK Not exactly straight-on, probably because I had it at one end of the scanner. It blows-up nicely: http://imgur.com/jrykApV Thanks, Bob |
#33
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Change gear pressure angle
On 1/24/2017 12:41 PM, Jim Wilkins wrote:
http://www.ereplacementparts.com/sea...et+change+gear One of those might be my gear. But their part numbers do not match mine. And their model list doesn't have mine, so I can't find the part in a drawing. Thanks anyhow, Bob |
#34
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Change gear pressure angle
On 1/23/2017 1:19 PM, Bob Engelhardt wrote:
I was looking at a picture of the lathe and the rack for the carriage power feed caught my eye. That rack won't have the same DP as the broken gear, but it will _probably_ have the same pressure angle. I mean, what's the chance that a lathe maker would use different pressure angles in his gears? The point being, of course, that the rack teeth have straight sides and easily measured angles. I took a photo of the rack & measured the angles: 20 degrees http://imgur.com/pRfDmj8 I haven't yet convinced my self that the rack HAS to have the same pressure angle. |
#35
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Change gear pressure angle
"Bob Engelhardt" wrote in message
news On 1/24/2017 12:41 PM, Jim Wilkins wrote: http://www.ereplacementparts.com/sea...et+change+gear One of those might be my gear. But their part numbers do not match mine. And their model list doesn't have mine, so I can't find the part in a drawing. Thanks anyhow, Bob The page gives their phone number. |
#36
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Change gear pressure angle = FOLLOWUP
I ordered a 20 degree cutter. 20 degrees seems the mostly likely angle.
Today I just happened to be using some epoxy putty for another project & I had a little left over. So I rolled the gear in it, to get a rack & measure it. Even though the putty was stiffer than plasticine and set up hard, it was not ideal. It tended to deform some from the perfect rack that it was supposed to be. Here is a photo of the molded epoxy, ground flat on one side & with straight lines fitted to the profile: http://imgur.com/a/ixovG Right-leaning lines are 18-19-19-20 degrees and left leaning ones 14 (all). Inconclusive, although closer to 14.5 on average. Bob |
#37
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Change gear pressure angle
On 2017-01-25, Bob Engelhardt wrote:
On 1/23/2017 11:54 PM, DoN. Nichols wrote: If you have a scanner, put the gear flat in the middle of the scanner's plate, and scan it. That will probably be as good an image as you can get, and will make sure that the "camera" is square with the gear. Use the highest resolution (maximum DPI setting) on the scanner. ... That is a good idea! Why didn't I think of that? I did do a scan, at 1200dpi (not max) and got a great image: http://imgur.com/Zi8ZueK Not exactly straight-on, probably because I had it at one end of the scanner. Right! That is why I suggested it be in the center of the scanner's plate. It blows-up nicely: http://imgur.com/jrykApV Yes -- enough to read into a CAD program and draw the tangent lines to pick up the pressure angle. Good Luck, DoN. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#38
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Change gear pressure angle
On 2017-01-25, Bob Engelhardt wrote:
On 1/23/2017 1:19 PM, Bob Engelhardt wrote: I was looking at a picture of the lathe and the rack for the carriage power feed caught my eye. That rack won't have the same DP as the broken gear, but it will _probably_ have the same pressure angle. I mean, what's the chance that a lathe maker would use different pressure angles in his gears? The point being, of course, that the rack teeth have straight sides and easily measured angles. I took a photo of the rack & measured the angles: 20 degrees http://imgur.com/pRfDmj8 I haven't yet convinced my self that the rack HAS to have the same pressure angle. It only *has* to be the same pressure angle as the pinion in the carriage -- but it is unlikely that a maker would use different pressure angles in different parts of a lathe. The main difference is how much force is generated trying to move the axles of the gears apart. And probably a difference in how much rubbing is going on between the surfaces of the teeth. They proably buy all the gears from one vendor, or just buy the equipment to make the gears from one vendor. The only time I might think that there would be different PAs would be in an *old* company, which continues to use some parts from earlier designs, and uses newer parts for things which have been re-designed in later years. Enjoy, DoN. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#39
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Change gear pressure angle = FOLLOWUP
On 1/26/2017 6:39 PM, Bob Engelhardt wrote:
I ordered a 20 degree cutter. 20 degrees seems the mostly likely angle. ... I've posted this question on the HSM forum and a fellow there (Paul Alciatore) played with my high-res 4-tooth scan and showed that my gear has 20 PA _stub_ form teeth. I never hear of stub form teeth, but they're regular teeth with the root & crest shortened. Makes them stronger, they say. His post is on page 3 of the HSM thread: http://bbs.homeshopmachinist.net/thr...re-angle/page3 |
#40
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Change gear pressure angle
On Thursday, January 26, 2017 at 10:26:26 PM UTC-5, DoN. Nichols wrote:
On 2017-01-25, Bob Engelhardt wrote: On 1/23/2017 1:19 PM, Bob Engelhardt wrote: I was looking at a picture of the lathe and the rack for the carriage power feed caught my eye. That rack won't have the same DP as the broken gear, but it will _probably_ have the same pressure angle. I mean, what's the chance that a lathe maker would use different pressure angles in his gears? The point being, of course, that the rack teeth have straight sides and easily measured angles. I took a photo of the rack & measured the angles: 20 degrees http://imgur.com/pRfDmj8 I haven't yet convinced my self that the rack HAS to have the same pressure angle. It only *has* to be the same pressure angle as the pinion in the carriage -- but it is unlikely that a maker would use different pressure angles in different parts of a lathe. The main difference is how much force is generated trying to move the axles of the gears apart. And probably a difference in how much rubbing is going on between the surfaces of the teeth. They proably buy all the gears from one vendor, or just buy the equipment to make the gears from one vendor. The only time I might think that there would be different PAs would be in an *old* company, which continues to use some parts from earlier designs, and uses newer parts for things which have been re-designed in later years. Enjoy, DoN. It's been almost 40 years since I covered gear making for American Machinist, so I forget much of the technology, but, FWIW, all of the machine tool builders I visited in those days hobbed their own gears. As for using different pressure angles, one hob can cut a variety of gear diameters, but only one pressure angle. So they normally settled on one angle for their gears and stuck with it. Some of the gears in a lathe have to handle a decent load, but the change gears are just timing gears. The load actually is very light. And, as long as any pair of gears are within a reasonable size range of each other, they don't encounter problems with undercutting or excessive sliding motion. All of the gear trains in a lathe, and in most machine tools, are pretty simple and standard -- although stub gear-tooth shapes were pretty common. This was all pre-CNC. -- Ed Huntress |
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