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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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A different single-point threading question....
All,
I also have a question concerning single-point threading. I recently started practicing making a few *small* parts for a miniature hit n miss engine I'm going to build (never had to make stuff this small before). One of the pieces is a downsized "grease cup" as is seen on some bigger machinery for greasing the bearings. Simply a threaded fixture to screw into the bearing cap, and a reservoir with a grease cap to be tightened to force grease down through a small hole into the bearing. As I very seldom had to thread mating parts without having the "other half" to try for fit, I'm in the process of "bettering" my accuracy so when I make the female thread, the male thread will fit as it should. I have a nice threading book (using 29 degrees angle) from Sears/Atlas showing a lot of info, but I also wanted to try something. Example: 1/4-20 threaded male piece. Charts show the major diameter of .2500 with a minor diameter of .1850 which corresponds to the National Form Tool Double Depth of Thread of .0650. (.2500 minus .0650 equals .1850). The manual I have shows depth of compound feed for the thread to be .037. So all is well and good so far. The chart also shows calculations for VEE form tool being Double Depth of Thread of .0758. Therefore, .2500 minus .0758 leaves minor diameter of .1742. The compound feed is shown to be .043 for the VEE thread. Again, okay so far. Now... I have Guy Lautard's bedside reader showing a formula for diameter reduction and also length reduction. Using the VEE form example above, I need to reduct the diameter of the shaft by .0650 in the threading process. Dividing this number by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth of thread. Using Lautard's system for small crossslide infeeds by using the compound, his formula is: Amount of crossslide infeed needed divided by sin of compound angle setting. Therefore .0325 divided by sin(29 degrees) should give me the correct amount of compound infeed to equal the amount of crossslide infeed I'm attempting to get. Formula yields .0670. Wrong answer..... what am I overlooking? The charts in the manual work well and the fit is good, but I was just trying to use a method which prevents looking up everything. Thanks. Ken. |
#2
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A different single-point threading question....
Hi Ken
for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". at the same time the thread form says that each of the thread crests should be flat and the width of the flat should be equal to 1/8 th of the thread pitch. So that leaves 7/8 ths of the thread pitch to form the top of the equilateral triangle that defines the shape of the thread. So in a 1/4-20 threaded male the pitch is .050" and 7/8 ths of that is ..04375" So all the sides of the equilateral triangle are .04375" So the distance from first touch (with a sharp tool) using a 29.5 degree compound is close enough to .04375" to be just that. If for some reason you need the double depth then it is cos 30 or .866 times the length of the sides (.04375") which gives the height of the equilateral triangle and twice that is the double depth. (.866*.04375*2= .075775") Nothing to look up! Bill "Ken Sterling" wrote in message s.com... All, I also have a question concerning single-point threading. I recently started practicing making a few *small* parts for a miniature hit n miss engine I'm going to build (never had to make stuff this small before). One of the pieces is a downsized "grease cup" as is seen on some bigger machinery for greasing the bearings. Simply a threaded fixture to screw into the bearing cap, and a reservoir with a grease cap to be tightened to force grease down through a small hole into the bearing. As I very seldom had to thread mating parts without having the "other half" to try for fit, I'm in the process of "bettering" my accuracy so when I make the female thread, the male thread will fit as it should. I have a nice threading book (using 29 degrees angle) from Sears/Atlas showing a lot of info, but I also wanted to try something. Example: 1/4-20 threaded male piece. Charts show the major diameter of .2500 with a minor diameter of .1850 which corresponds to the National Form Tool Double Depth of Thread of .0650. (.2500 minus .0650 equals .1850). The manual I have shows depth of compound feed for the thread to be .037. So all is well and good so far. The chart also shows calculations for VEE form tool being Double Depth of Thread of .0758. Therefore, .2500 minus .0758 leaves minor diameter of .1742. The compound feed is shown to be .043 for the VEE thread. Again, okay so far. Now... I have Guy Lautard's bedside reader showing a formula for diameter reduction and also length reduction. Using the VEE form example above, I need to reduct the diameter of the shaft by .0650 in the threading process. Dividing this number by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth of thread. Using Lautard's system for small crossslide infeeds by using the compound, his formula is: Amount of crossslide infeed needed divided by sin of compound angle setting. Therefore .0325 divided by sin(29 degrees) should give me the correct amount of compound infeed to equal the amount of crossslide infeed I'm attempting to get. Formula yields .0670. Wrong answer..... what am I overlooking? The charts in the manual work well and the fit is good, but I was just trying to use a method which prevents looking up everything. Thanks. Ken. |
#3
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A different single-point threading question....
"Ken Sterling" wrote in message s.com... All, I also have a question concerning single-point threading. I recently started practicing making a few *small* parts for a miniature hit n miss engine I'm going to build (never had to make stuff this small before). One of the pieces is a downsized "grease cup" as is seen on some bigger machinery for greasing the bearings. Simply a threaded fixture to screw into the bearing cap, and a reservoir with a grease cap to be tightened to force grease down through a small hole into the bearing. As I very seldom had to thread mating parts without having the "other half" to try for fit, I'm in the process of "bettering" my accuracy so when I make the female thread, the male thread will fit as it should. I have a nice threading book (using 29 degrees angle) from Sears/Atlas showing a lot of info, but I also wanted to try something. Example: 1/4-20 threaded male piece. Charts show the major diameter of .2500 with a minor diameter of .1850 which corresponds to the National Form Tool Double Depth of Thread of .0650. (.2500 minus .0650 equals .1850). The manual I have shows depth of compound feed for the thread to be .037. So all is well and good so far. The chart also shows calculations for VEE form tool being Double Depth of Thread of .0758. Therefore, .2500 minus .0758 leaves minor diameter of .1742. The compound feed is shown to be .043 for the VEE thread. Again, okay so far. Now... I have Guy Lautard's bedside reader showing a formula for diameter reduction and also length reduction. Using the VEE form example above, I need to reduct the diameter of the shaft by .0650 in the threading process. Dividing this number by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth of thread. Using Lautard's system for small crossslide infeeds by using the compound, his formula is: Amount of crossslide infeed needed divided by sin of compound angle setting. Therefore .0325 divided by sin(29 degrees) should give me the correct amount of compound infeed to equal the amount of crossslide infeed I'm attempting to get. Formula yields .0670. Wrong answer..... what am I overlooking? The charts in the manual work well and the fit is good, but I was just trying to use a method which prevents looking up everything. Thanks. Ken. Hi Ken, Cutting threads by major and minor diameter is not a good idea due to the random flat that usually accompanies a threading tool. Without a comparator to know its width, the formulas are useless. I strongly recommend you use thread wires and threading charts to cut your threads. The use of any of the trick calculations are only as reliable as the information you have concerning your threading tool, and the degree of precision with which you pick up the surface to be threaded, taking into account the variation in major diameter. On small threads its entirely possible you'd have more error than the small amount of tolerance common to some threads. Relying on threading charts removes all the questions, because you machine to known dimensions. Pretty much anything you need to know is published in Machinery's Handbook. This may sound like overkill to you, but it is a part of learning to cut threads properly. Harold |
#4
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A different single-point threading question....
Hi Ken
for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". at the same time the thread form says that each of the thread crests should be flat and the width of the flat should be equal to 1/8 th of the thread pitch. So that leaves 7/8 ths of the thread pitch to form the top of the equilateral triangle that defines the shape of the thread. So in a 1/4-20 threaded male the pitch is .050" and 7/8 ths of that is .04375" So all the sides of the equilateral triangle are .04375" So the distance from first touch (with a sharp tool) using a 29.5 degree compound is close enough to .04375" to be just that. If for some reason you need the double depth then it is cos 30 or .866 times the length of the sides (.04375") which gives the height of the equilateral triangle and twice that is the double depth. (.866*.04375*2= .075775") Nothing to look up! Bill "Ken Sterling" wrote in message ws.com... All, I also have a question concerning single-point threading. I recently started practicing making a few *small* parts for a miniature hit n miss engine I'm going to build (never had to make stuff this small before). One of the pieces is a downsized "grease cup" as is seen on some bigger machinery for greasing the bearings. Simply a threaded fixture to screw into the bearing cap, and a reservoir with a grease cap to be tightened to force grease down through a small hole into the bearing. As I very seldom had to thread mating parts without having the "other half" to try for fit, I'm in the process of "bettering" my accuracy so when I make the female thread, the male thread will fit as it should. I have a nice threading book (using 29 degrees angle) from Sears/Atlas showing a lot of info, but I also wanted to try something. Example: 1/4-20 threaded male piece. Charts show the major diameter of .2500 with a minor diameter of .1850 which corresponds to the National Form Tool Double Depth of Thread of .0650. (.2500 minus .0650 equals .1850). The manual I have shows depth of compound feed for the thread to be .037. So all is well and good so far. The chart also shows calculations for VEE form tool being Double Depth of Thread of .0758. Therefore, .2500 minus .0758 leaves minor diameter of .1742. The compound feed is shown to be .043 for the VEE thread. Again, okay so far. Now... I have Guy Lautard's bedside reader showing a formula for diameter reduction and also length reduction. Using the VEE form example above, I need to reduct the diameter of the shaft by .0650 in the threading process. Dividing this number by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth of thread. Using Lautard's system for small crossslide infeeds by using the compound, his formula is: Amount of crossslide infeed needed divided by sin of compound angle setting. Therefore .0325 divided by sin(29 degrees) should give me the correct amount of compound infeed to equal the amount of crossslide infeed I'm attempting to get. Formula yields .0670. Wrong answer..... what am I overlooking? The charts in the manual work well and the fit is good, but I was just trying to use a method which prevents looking up everything. Thanks. Ken. Thanks, Bill. I worked out the numbers on a bunch of different thread profiles and they seem to match the charts in my threading manual for my lathe. (Some of the numbers in the charts were of course, rounded off, but working out the formula carries out more decimal places than these eyes will ever be able to see, :-) ) Thanks for the info - I think it will be handy - Now to find some more "free" time to get back to the lathe..... Thanks again. Ken. |
#5
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A different single-point threading question....
"Ken Sterling" wrote in message ws.com... All, I also have a question concerning single-point threading. I recently started practicing making a few *small* parts for a miniature hit n miss engine I'm going to build (never had to make stuff this small before). One of the pieces is a downsized "grease cup" as is seen on some bigger machinery for greasing the bearings. Simply a threaded fixture to screw into the bearing cap, and a reservoir with a grease cap to be tightened to force grease down through a small hole into the bearing. As I very seldom had to thread mating parts without having the "other half" to try for fit, I'm in the process of "bettering" my accuracy so when I make the female thread, the male thread will fit as it should. I have a nice threading book (using 29 degrees angle) from Sears/Atlas showing a lot of info, but I also wanted to try something. Example: 1/4-20 threaded male piece. Charts show the major diameter of .2500 with a minor diameter of .1850 which corresponds to the National Form Tool Double Depth of Thread of .0650. (.2500 minus .0650 equals .1850). The manual I have shows depth of compound feed for the thread to be .037. So all is well and good so far. The chart also shows calculations for VEE form tool being Double Depth of Thread of .0758. Therefore, .2500 minus .0758 leaves minor diameter of .1742. The compound feed is shown to be .043 for the VEE thread. Again, okay so far. Now... I have Guy Lautard's bedside reader showing a formula for diameter reduction and also length reduction. Using the VEE form example above, I need to reduct the diameter of the shaft by .0650 in the threading process. Dividing this number by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth of thread. Using Lautard's system for small crossslide infeeds by using the compound, his formula is: Amount of crossslide infeed needed divided by sin of compound angle setting. Therefore .0325 divided by sin(29 degrees) should give me the correct amount of compound infeed to equal the amount of crossslide infeed I'm attempting to get. Formula yields .0670. Wrong answer..... what am I overlooking? The charts in the manual work well and the fit is good, but I was just trying to use a method which prevents looking up everything. Thanks. Ken. Hi Ken, Cutting threads by major and minor diameter is not a good idea due to the random flat that usually accompanies a threading tool. Without a comparator to know its width, the formulas are useless. I strongly recommend you use thread wires and threading charts to cut your threads. The use of any of the trick calculations are only as reliable as the information you have concerning your threading tool, and the degree of precision with which you pick up the surface to be threaded, taking into account the variation in major diameter. On small threads its entirely possible you'd have more error than the small amount of tolerance common to some threads. Relying on threading charts removes all the questions, because you machine to known dimensions. Pretty much anything you need to know is published in Machinery's Handbook. This may sound like overkill to you, but it is a part of learning to cut threads properly. Harold Thanks Harold. Your point is understood and well taken. My question in my original post, though, kind of reflected on the fact that when I determined Major Dia, and then Minor Dia, I knew how much the diameter had to be reduced to get to the Minor Dia. What I couldn't understand is why, using Guy Lautard's Diameter Reduction Formula (amount of diameter reduction, divided by the sin(29 degrees)) would not give me the proper amount of compound infeed. Still haven't figured out that one - I guess it really doesn't matter, but I hate it when I can see the formula, and it works with the example, but when applied to another situation - it sucks. Thanks again for your response. Ken. |
#6
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A different single-point threading question....
In article m,
Ken Sterling Ken Sterling wrote: [ ... ] Thanks Harold. Your point is understood and well taken. My question in my original post, though, kind of reflected on the fact that when I determined Major Dia, and then Minor Dia, I knew how much the diameter had to be reduced to get to the Minor Dia. What I couldn't understand is why, using Guy Lautard's Diameter Reduction Formula (amount of diameter reduction, divided by the sin(29 degrees)) would not give me the proper amount of compound infeed. Is your compound set to 29 degrees? If to some other angle, you will need to calculate using the sine of whatever angle you are actually using. And after all -- the pitch diameter is what really matters. Hence the measuring over wires. Enjoy, DoN. -- Email: | 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 --- |
#7
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A different single-point threading question....
"DoN. Nichols" wrote in message ... snip------- And after all -- the pitch diameter is what really matters. Hence the measuring over wires. Enjoy, DoN. Yep, my point, exactly. All the rest does is cloud the issue. None of it is close enough to use for proper threading. Harold |
#8
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A different single-point threading question....
"DoN. Nichols" wrote in message ... snip------- And after all -- the pitch diameter is what really matters. Hence the measuring over wires. Enjoy, DoN. Yep, my point, exactly. All the rest does is cloud the issue. None of it is close enough to use for proper threading. Harold Points well taken, but in this particular situation, I'm threading 5/16-40, internal, 3/16 deep to a solid bottom. Don't know any way to check this so just wanted to get the numbers as close as I can. Thanks. Ken. |
#9
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A different single-point threading question....
"Ken Sterling" wrote in message s.com... "DoN. Nichols" wrote in message ... snip------- And after all -- the pitch diameter is what really matters. Hence the measuring over wires. Enjoy, DoN. Yep, my point, exactly. All the rest does is cloud the issue. None of it is close enough to use for proper threading. Harold Points well taken, but in this particular situation, I'm threading 5/16-40, internal, 3/16 deep to a solid bottom. Don't know any way to check this so just wanted to get the numbers as close as I can. Thanks. Ken. In a case such as this, what I've done is turn my own plug gage. By using (proper) wires and cutting the thread to proper form you can enjoy considerable success, although the gage is subject to change, so it is good for only a minimum amount of use. It's a good idea to use something like O6 tool steel (Graph-Mo, for example), which tends to leave a better finish than carbon steel. A leaded steel might be a good choice for a very small amount of usage. It is also critical to have the use of a comparator, or at least good magnification, so the proper amount of flat can be ground on the threading tool, which, in the case of such a fine thread, is very slight. If the thread in question is critical (such as having to pass inspection) the chance of hitting the proper pitch diameter by trusting the compound movement would be very small due to the minimal tolerance, although certainly possible. The problem is you don't really have any idea if the thread being generated is where you think it is, so it's very easy to stop at the proper number on the dial and be off, either too large or too small on the pitch diameter. Hope this helps, Ken. It's not intended to give you a bad time. Good luck! Harold |
#10
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A different single-point threading question....
"Ken Sterling" wrote in message ws.com... "DoN. Nichols" wrote in message ... snip------- And after all -- the pitch diameter is what really matters. Hence the measuring over wires. Enjoy, DoN. Yep, my point, exactly. All the rest does is cloud the issue. None of it is close enough to use for proper threading. Harold Points well taken, but in this particular situation, I'm threading 5/16-40, internal, 3/16 deep to a solid bottom. Don't know any way to check this so just wanted to get the numbers as close as I can. Thanks. Ken. In a case such as this, what I've done is turn my own plug gage. By using (proper) wires and cutting the thread to proper form you can enjoy considerable success, although the gage is subject to change, so it is good for only a minimum amount of use. It's a good idea to use something like O6 tool steel (Graph-Mo, for example), which tends to leave a better finish than carbon steel. A leaded steel might be a good choice for a very small amount of usage. It is also critical to have the use of a comparator, or at least good magnification, so the proper amount of flat can be ground on the threading tool, which, in the case of such a fine thread, is very slight. If the thread in question is critical (such as having to pass inspection) the chance of hitting the proper pitch diameter by trusting the compound movement would be very small due to the minimal tolerance, although certainly possible. The problem is you don't really have any idea if the thread being generated is where you think it is, so it's very easy to stop at the proper number on the dial and be off, either too large or too small on the pitch diameter. Hope this helps, Ken. It's not intended to give you a bad time. Good luck! Harold No "bad time" taken, Harold. I appreciate the info and tips. This application is certainly not critical, but for my own use and I think (after a couple of different tries) I'm getting the "hang" of it. :-) I like the idea of a "temporary" plug gauge.... I may just take that route. Thanks Ken. |
#11
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A different single-point threading question....
Bill Darby wrote:
for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". Bill, you have sadi this many times and now I wonder if we both mean the same thing by "major diameter". I mean the mesurement I get if I close a flat faced micrometer over the outside of a male thread having removed any burrs if present. What do you mean? I ask because I understand that the only 1/4" thread with a full 0.2500" o.d. would be one with a sharp V-topped thread. Any comercial 1/4" thread I have measured has always been rather less than 0.2500 o.d., typically by about 1/8 of the nominal thread depth. Also, any thread I have single pointed has always needed to be cut a little deeper to fit than you indicate, assuming I understand you correctly. I would like to understand this better. Ted |
#12
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A different single-point threading question....
Harold & Susan Vordos wrote:
Yep, my point, exactly. All the rest does is cloud the issue. None of it is close enough to use for proper threading. Guess I'm going to have to cut some music wire and make a holder. Otherwise this could be awkward with only two hands. :-) Any ideas on this holder? Ted |
#13
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A different single-point threading question....
for a 1/4 " shaft the major diameter is supposed to be a 1/4 ".
Bill, you have sadi this many times and now I wonder if we both mean the same thing by "major diameter". This is confusing, to say the least. Here is a good approach: Always take "diameter" to mean the actual outside, full diameter of the rod or bolt to be threaded; as in 1/4-20, diameter is 0.250; 3/8-16 diameter is 0.375, etc. For bolt or rod to thread use the formula: Bolt size = Diameter - ((1.299 x %) / pitch)) Where diameter is as explained above, % is expressed as a decimal, and pitch is the number of threads per inch. Bob Swinney |
#14
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A different single-point threading question....
"Ted Edwards" wrote in message ... Harold & Susan Vordos wrote: Yep, my point, exactly. All the rest does is cloud the issue. None of it is close enough to use for proper threading. Guess I'm going to have to cut some music wire and make a holder. Otherwise this could be awkward with only two hands. :-) Any ideas on this holder? Ted No holder. The use of thread wires with your object still in a lathe is very easy, with a holder only adding to problems. One of the problems would be the influence the holder would have over the wires. That may sound trivial, but it's not, and a caution of this very thing accompanies good wires. The wires must be free to conform to the thread. Even a little tape on one end can influence a reading, especially on larger wires. People with your ability with math would have no trouble calculating the proper measurement over wires when choosing random diameters for measuring, but folks like me, with only a high school education, one that did not consist of any advanced mathematics, would have a difficult time calculating the proper readings. Further, and in this case it likely makes no difference at all, if you were chasing threads that needed acceptance by inspection, the readings would most likely be disputed by an inspection department. Standard thread wires (not the little cheap PeeDee sets, but the wires sold by such firms as Deltronics) are precision instruments, with diameters held to millionths, and come with certification. The wires are of such a quality that they can be used for certification of thread gages. These wires come with a constant that is added to the maximum and minimum thread pitch, which one fetches from a source such as Machinery's Handbook. Measuring threads by this method is very simple and is acceptable by inspection. It is likely well overkill for the home shop type, but is good and acceptable practice in any shop. Back to the use of thread wires. To use them, one sets the mike so it's opened slightly larger than the intended reading, places two wires on the top side of the item to be measured, spread a distance slightly narrower than the diameter of the spindle, then straddles the wires with the spindle. lightly pressing the wires to keep them from falling. The third wire, which is held in one's lips, is then slid between the anvil and the part, splitting the distance between the top wires, so a three point reading can be taken. When the open distance is fairly close, the wires will stay in place with no trouble at all once the third wire is installed. One then tightens the spindle, keeping the face parallel with the top two wires, rocking the mike for feel, until it is measuring the distance over the wires. Once learned this way, it's very easy, and fast, and requires no holder. One word of caution, and it matters not the source of your wires, be they the expensive commercial wires such as the Deltronics, P&W, or just the simple set sold be PeeDee: ALWAYS clean out your chip pan when measuring threads. It's amazing how a long wire looks like the rest of the chips when you drop them. Good luck! Harold |
#15
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A different single-point threading question....
"Robert Swinney" wrote in message ... for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". Bill, you have sadi this many times and now I wonder if we both mean the same thing by "major diameter". This is confusing, to say the least. Here is a good approach: Always take "diameter" to mean the actual outside, full diameter of the rod or bolt to be threaded; as in 1/4-20, diameter is 0.250; 3/8-16 diameter is 0.375, etc. For bolt or rod to thread use the formula: Bolt size = Diameter - ((1.299 x %) / pitch)) Where diameter is as explained above, % is expressed as a decimal, and pitch is the number of threads per inch. Bob Swinney I would assume that, for the home shop types, it may be confusing, but it's not when a thread is specified. Part of the information provided by threading charts is the *proper* major diameter, which varies depending on the nature of a thread. In other words, not all 1/4-20 threads are created equally. One example: 1/4-20 2A Major diameter range: .2489"/.2408" 1/4-20 3A Major diameter range: .2500"/.2419" None of the features of threads are left to discretion. Simply referencing the charts will provide the necessary information in order to chase proper threads. The only exception is the width of the flat for modified V form threads, which is not included in most charts, although the minor diameter is specified. Harold |
#16
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A different single-point threading question....
Hi Ted
I wonder if we both mean the same thing by "major diameter". I mean the measurement I get if I close a flat faced micrometer over the outside of a male thread Yes I meant that they were one in the same IE : "major diameter. I mean the measurement I get if I close a flat faced micrometer over the outside of a male thread" Yes they are one in the same. In regard to Harold's point depending on the class of thread the actual measurement will not necessarily be the same as the designated diameter. (as he elaborated upon) IE: A given class of 1/4" thread might call for a major diameter something less then .25" I ask because I understand that the only 1/4" thread with a full 0.2500" o.d. would be one with a sharp V-topped thread. No this is not a true assertion. The 1/8 th * pitch flat on the crest of the thread is supposed to be made at the actual major diameter. Without getting into various classes of threads and their associated major diameters (see Harold's post) this is why I wanted to stick to a generic 1/4 thread with a 1/4 major diameter because it illustrates very clearly that the 1/8 * pitch flat occurs at the major diameter. As I see it the thread form designers were quite smart and cost conscious. They probably wanted to throw away the very weak pip portion of the V-topped thread because it meant that the diameter of the stock was quit large to accommodate the sharp V-tops. So they truncated useless top 1/8 th of the thread height and made the resulting flat occur at the major diameter which is essentially the same size of the stock used to form the thread. Also, any thread I have single pointed has always needed to be cut a little deeper to fit than you indicate, assuming I understand you correctly. I would like to understand this better. I also have had this same experience. The answer lies in the various classes of thread you may be trying to mate your thread with. What I have said (I believe to be correct) but it is a generic explanation. As you would be aware, all the various classes of threads call for various dimensions, Not that the various dimensions change the thread form but they call for various major diameters. The Major diameter varies with each class of thread but the one thing about the thread form that is always constant, is the width of the flat. It is always 1/8 th * the pitch. This means that equilateral triangle that forms the thread shape is always the same, ie 7/8 ths of the pitch length on edge. All of which simply means that all classes of external threads are cut the same, except that the start diameter should conform to the stated major diameter of the class of thread you want to cut. Sorry I talked so much I am kind of on the fly! Bill Ted Edwards wrote: Bill Darby wrote: for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". Bill, you have sadi this many times and now I wonder if we both mean the same thing by "major diameter". I mean the mesurement I get if I close a flat faced micrometer over the outside of a male thread having removed any burrs if present. What do you mean? I ask because I understand that the only 1/4" thread with a full 0.2500" o.d. would be one with a sharp V-topped thread. Any comercial 1/4" thread I have measured has always been rather less than 0.2500 o.d., typically by about 1/8 of the nominal thread depth. Also, any thread I have single pointed has always needed to be cut a little deeper to fit than you indicate, assuming I understand you correctly. I would like to understand this better. Ted |
#17
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A different single-point threading question....
Harold sez:
" The only exception is the width of the flat for modified V form threads, which is not included in most charts, although the minor diameter is specified." I didn't do a lot of research on this but, I think the formula I gave is for the diameter of a bolt for cutting sharp "V" threads on a lathe. Without going into a lot of "class distinction" I believe the formula will also work quite well for the basic starting diameter for rods to be threaded (chased ??) with a die. As Harold said, it is OK for us home-shop types. Granted, it may get into trouble with extremely hard material. Then, one would be well advised to go to "class". Bob Swinney "Harold & Susan Vordos" wrote in message ... "Robert Swinney" wrote in message ... for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". Bill, you have sadi this many times and now I wonder if we both mean the same thing by "major diameter". This is confusing, to say the least. Here is a good approach: Always take "diameter" to mean the actual outside, full diameter of the rod or bolt to be threaded; as in 1/4-20, diameter is 0.250; 3/8-16 diameter is 0.375, etc. For bolt or rod to thread use the formula: Bolt size = Diameter - ((1.299 x %) / pitch)) Where diameter is as explained above, % is expressed as a decimal, and pitch is the number of threads per inch. Bob Swinney I would assume that, for the home shop types, it may be confusing, but it's not when a thread is specified. Part of the information provided by threading charts is the *proper* major diameter, which varies depending on the nature of a thread. In other words, not all 1/4-20 threads are created equally. One example: 1/4-20 2A Major diameter range: .2489"/.2408" 1/4-20 3A Major diameter range: .2500"/.2419" None of the features of threads are left to discretion. Simply referencing the charts will provide the necessary information in order to chase proper threads. Harold |
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A different single-point threading question....
Bill, Your rationale is quite clear and one that many "thread cutters" would
be the better off to understand. Key to working one's way through the thread jungle is that originally, depending on how far back you want to go, all threads were cut on the lathe. I would guess that, originally, they all started out as sharp "Vs". As I understand it, departures from sharp "Vs" began in England with Sir Jos. Whitworth's 55 degree thread. Than gradually after that, standardized types and classes began to appear. Now, with ISO, I would suppose the standards are now, welll, errr, standardized. From what I read, standards were not fully defined until after WWII. Bob Swinney "Bill" wrote in message ... Hi Ted I wonder if we both mean the same thing by "major diameter". I mean the measurement I get if I close a flat faced micrometer over the outside of a male thread Yes I meant that they were one in the same IE : "major diameter. I mean the measurement I get if I close a flat faced micrometer over the outside of a male thread" Yes they are one in the same. In regard to Harold's point depending on the class of thread the actual measurement will not necessarily be the same as the designated diameter. (as he elaborated upon) IE: A given class of 1/4" thread might call for a major diameter something less then .25" I ask because I understand that the only 1/4" thread with a full 0.2500" o.d. would be one with a sharp V-topped thread. No this is not a true assertion. The 1/8 th * pitch flat on the crest of the thread is supposed to be made at the actual major diameter. Without getting into various classes of threads and their associated major diameters (see Harold's post) this is why I wanted to stick to a generic 1/4 thread with a 1/4 major diameter because it illustrates very clearly that the 1/8 * pitch flat occurs at the major diameter. As I see it the thread form designers were quite smart and cost conscious. They probably wanted to throw away the very weak pip portion of the V-topped thread because it meant that the diameter of the stock was quit large to accommodate the sharp V-tops. So they truncated useless top 1/8 th of the thread height and made the resulting flat occur at the major diameter which is essentially the same size of the stock used to form the thread. Also, any thread I have single pointed has always needed to be cut a little deeper to fit than you indicate, assuming I understand you correctly. I would like to understand this better. I also have had this same experience. The answer lies in the various classes of thread you may be trying to mate your thread with. What I have said (I believe to be correct) but it is a generic explanation. As you would be aware, all the various classes of threads call for various dimensions, Not that the various dimensions change the thread form but they call for various major diameters. The Major diameter varies with each class of thread but the one thing about the thread form that is always constant, is the width of the flat. It is always 1/8 th * the pitch. This means that equilateral triangle that forms the thread shape is always the same, ie 7/8 ths of the pitch length on edge. All of which simply means that all classes of external threads are cut the same, except that the start diameter should conform to the stated major diameter of the class of thread you want to cut. Sorry I talked so much I am kind of on the fly! Bill Ted Edwards wrote: Bill Darby wrote: for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". Bill, you have sadi this many times and now I wonder if we both mean the same thing by "major diameter". I mean the mesurement I get if I close a flat faced micrometer over the outside of a male thread having removed any burrs if present. What do you mean? I ask because I understand that the only 1/4" thread with a full 0.2500" o.d. would be one with a sharp V-topped thread. Any comercial 1/4" thread I have measured has always been rather less than 0.2500 o.d., typically by about 1/8 of the nominal thread depth. Also, any thread I have single pointed has always needed to be cut a little deeper to fit than you indicate, assuming I understand you correctly. I would like to understand this better. Ted |
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A different single-point threading question....
No holder. The use of thread wires with your object still in a lathe is very easy, with a holder only adding to problems. One of the problems would be the influence the holder would have over the wires. That may sound trivial, but it's not, and a caution of this very thing accompanies good wires. The wires must be free to conform to the thread. Even a little tape on one end can influence a reading, especially on larger wires. People with your ability with math would have no trouble calculating the proper measurement over wires when choosing random diameters for measuring, but folks like me, with only a high school education, one that did not consist of any advanced mathematics, would have a difficult time calculating the proper readings. Further, and in this case it likely makes no difference at all, if you were chasing threads that needed acceptance by inspection, the readings would most likely be disputed by an inspection department. Standard thread wires (not the little cheap PeeDee sets, but the wires sold by such firms as Deltronics) are precision instruments, with diameters held to millionths, and come with certification. The wires are of such a quality that they can be used for certification of thread gages. These wires come with a constant that is added to the maximum and minimum thread pitch, which one fetches from a source such as Machinery's Handbook. Measuring threads by this method is very simple and is acceptable by inspection. It is likely well overkill for the home shop type, but is good and acceptable practice in any shop. Back to the use of thread wires. To use them, one sets the mike so it's opened slightly larger than the intended reading, places two wires on the top side of the item to be measured, spread a distance slightly narrower than the diameter of the spindle, then straddles the wires with the spindle. lightly pressing the wires to keep them from falling. The third wire, which is held in one's lips, is then slid between the anvil and the part, splitting the distance between the top wires, so a three point reading can be taken. When the open distance is fairly close, the wires will stay in place with no trouble at all once the third wire is installed. One then tightens the spindle, keeping the face parallel with the top two wires, rocking the mike for feel, until it is measuring the distance over the wires. Once learned this way, it's very easy, and fast, and requires no holder. One word of caution, and it matters not the source of your wires, be they the expensive commercial wires such as the Deltronics, P&W, or just the simple set sold be PeeDee: ALWAYS clean out your chip pan when measuring threads. It's amazing how a long wire looks like the rest of the chips when you drop them. Good luck! Harold For practical home shops is there any advantage to using wires instead if a thread Mic ? The cheap imports look a lot more convienient . Ken Cutt |
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A different single-point threading question....
On Sun, 30 May 2004 17:33:36 GMT, Ted Edwards
wrote: Harold & Susan Vordos wrote: Yep, my point, exactly. All the rest does is cloud the issue. None of it is close enough to use for proper threading. Guess I'm going to have to cut some music wire and make a holder. Otherwise this could be awkward with only two hands. :-) Any ideas on this holder? Ted A small lump of Plasticene (modelling clay)! Jim |
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A different single-point threading question....
"Harold & Susan Vordos" wrote The third wire, which is held in one's lips, is then slid between the anvil and the part, splitting the distance between the top wires, so....... That's the hard part.... "which is held in one's lips"........ Harold, you forgot to mention the first step..... turn the lathe off..... ! Mark |
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A different single-point threading question....
"M" mark@maxmachinedotcom wrote in message ... "Harold & Susan Vordos" wrote The third wire, which is held in one's lips, is then slid between the anvil and the part, splitting the distance between the top wires, so....... That's the hard part.... "which is held in one's lips"........ Harold, you forgot to mention the first step..... turn the lathe off..... ! Mark Chuckle! Yep, should have mentioned that, Could prove real interesting otherwise. :-) Harold |
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A different single-point threading question....
"Ken Cutt" wrote in message ... snip--- For practical home shops is there any advantage to using wires instead if a thread Mic ? The cheap imports look a lot more convienient . Ken Cutt I don't like thread mikes. Never have, although they are fine for home usage, probably even so good as to be considered over-kill. My personal preference is to use wires, not even triangles. Both thread mikes and triangles have the potential to measure a thread off the pitch diameter when there's the slightest error in thread form. That's not true with wires. All of this is probably not all that important as long as you're not trying to sell threads under government contract, which is where I acquired all my "bad" habits. In spite of the fact that I closed my commercial shop over 20 years ago, the years of running government contract work still steers my thinking to this day. I've long maintained that if you choose methods that are accepted by industry/government, that you'll achieve a level of excellence that is difficult to challenge, and have a yield that is consistently better than those that don't. It's worked for me for years, so I hesitate to abandon my ways. It's hard to relax, and I don't know that I really want to because it's no more difficult to work to exacting standards than to be a hack if you always practice working in what I consider to be a better way. Therefore, I stay the coarse, using wires. I don't find them any more difficult to use than thread mikes, which, to me, have a terrible feel. (Proper) wires can be used for calibrating gages, thread mikes can not. That alone speaks volumes about their ability to provide erroneous readings. Harold |
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A different single-point threading question....
wrote in message ... On Sun, 30 May 2004 17:33:36 GMT, Ted Edwards wrote: Harold & Susan Vordos wrote: Yep, my point, exactly. All the rest does is cloud the issue. None of it is close enough to use for proper threading. Guess I'm going to have to cut some music wire and make a holder. Otherwise this could be awkward with only two hands. :-) Any ideas on this holder? Ted A small lump of Plasticene (modelling clay)! Jim That's a bigger pain in the butt than loose wires, and by a long shot. I've tried any and everything in my years on the machines. There's nothing that replaces learning how to do it without aids of any sort. Nothing! That includes a loop of masking tape, by the way. Like I said, I've tried it all. None of it works as well as free wires. Harold |
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A different single-point threading question....
In article , Harold & Susan Vordos says...
I don't like thread mikes. Never have, although they are fine for home usage, probably even so good as to be considered over-kill. My personal preference is to use wires, not even triangles. Both thread mikes and triangles have the potential to measure a thread off the pitch diameter when there's the slightest error in thread form. That's not true with wires. Harold I cannot argue with using the best method for the job, even at home, but it would seem to me that the wires cannot meausure properly if there *is* an error in the thread form. For example, what if the threads were cut to some odd angle, say, 63 degrees or so. Unless one used a comparator to actually measure the thread angle, wouldn't the wires give some reading that would allow one to *think* the threads were properly formed when in fact they were not? What role do thread gages play in all this? Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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A different single-point threading question....
"jim rozen" wrote in message ... In article , Harold & Susan Vordos says... I don't like thread mikes. Never have, although they are fine for home usage, probably even so good as to be considered over-kill. My personal preference is to use wires, not even triangles. Both thread mikes and triangles have the potential to measure a thread off the pitch diameter when there's the slightest error in thread form. That's not true with wires. Harold I cannot argue with using the best method for the job, even at home, but it would seem to me that the wires cannot meausure properly if there *is* an error in the thread form. For example, what if the threads were cut to some odd angle, say, 63 degrees or so. Unless one used a comparator to actually measure the thread angle, wouldn't the wires give some reading that would allow one to *think* the threads were properly formed when in fact they were not? What role do thread gages play in all this? Jim I fully agree, Jim. The tolerance of the thread form is very much a part of the equation, and it's relatively narrow. Certainly 3 degrees would be WAY out of tolerance. It's been a lot of years, but I seem to recall that the thread form is held to +/- 15 minutes. I think it's safe to say that most of us, especially us older dudes, can't even see it on a thread gage unless we're grinding a relatively large threading tool with broad faces. The harsh reality is that the wires *will* be measuring at the pitch diameter, it just won't be right because of form error. I think you can see that. The problem with triangles is they bear anywhere but at the pitch line if the angle is off, and it makes no difference which way. Mikes are slightly different because they have a truncated spindle and anvil as I recall. If the thread form is too narrow, they will make contact near the major diameter instead of at the pitch line. Wires always measure the pitch line, even with bad form. Actually, thread gages pick up thread form error to some degree. Considering the no go is generally truncated, if a go gage fits, but the form is off, the no go is likely to go on as well, depending on the thread form angle. Other features may be off, so it won't go. Because the gage checks angle to some degree, when you finally get a thread to fit the gage that is off form, it is usually off so far in other features that the no go betrays the bad form. If you kick this around in your head a bit, I think you'll see what I'm talking about. Ring gages, in particular, are very effective at determining many features, although they may not describe the degree of error that may exist. They actually check all major features, major diameter, pitch diameter and minor diameter, and by variations in how they fit, thread form. When a go gage fits well, but the no go does, too, you know something's amiss. All you have to do is determine what's wrong. There's nothing like having a comparator to help in working with threads when it's important that they be right. Harold |
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A different single-point threading question....
In article , Harold & Susan Vordos says...
The harsh reality is that the wires *will* be measuring at the pitch diameter, it just won't be right because of form error. I think you can see that. The problem with triangles is they bear anywhere but at the pitch line if the angle is off, and it makes no difference which way. I guess for me, the pitch diameter is a specific theoretical size based on the particular thread - so that if the form is off, the wires will be measuring at *some* pitch diameter - just the wrong one. Actually, thread gages pick up thread form error to some degree. Considering the no go is generally truncated, if a go gage fits, but the form is off, the no go is likely to go on as well, depending on the thread form angle. Other features may be off, so it won't go. Because the gage checks angle to some degree, when you finally get a thread to fit the gage that is off form, it is usually off so far in other features that the no go betrays the bad form. If you kick this around in your head a bit, I think you'll see what I'm talking about. Yes. I've seen this when single pointing threads with some error along the way - having the tool not set 90 deg to the work comes to mind. Or trying to fit a thread that was improperly cut to begin with as another example. Say if an ID thread has too large of a flat on the major diameter, or if the minor diameter has the threads too pointy (no flat). Then I've seen where the thread one is trying to single point to fit the part simply won't go unless it is either cut too far, but simply kissing the major diameter of the male thread will allow it to drop in nicely. Ring gages, in particular, are very effective at determining many features, although they may not describe the degree of error that may exist. They actually check all major features, major diameter, pitch diameter and minor diameter, and by variations in how they fit, thread form. When a go gage fits well, but the no go does, too, you know something's amiss. All you have to do is determine what's wrong. There's nothing like having a comparator to help in working with threads when it's important that they be right. For me at home I'm typically trying to fit some existing part with my single pointed thread. So I simply use the part as the 'gage' in a rough sense. Of course that leads to the problem that at some time I wind up trying to fit to another part I've already made, and I wind up with my own private local NBS for threads. :^) Anyway I've always found that getting the tool ground to the correct angle, getting it set perpendicular to the work, turning the major diameter correctly, and then leaving a bit of the part undersized (to be removed afterwards) to the minor diameter, are a few of the best ways to get a decent threading job. I'll have to see about this wire stuff - sounds like a better way to go. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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A different single-point threading question....
"jim rozen" wrote in message ... In article , Harold & Susan Vordos says... The harsh reality is that the wires *will* be measuring at the pitch diameter, it just won't be right because of form error. I think you can see that. The problem with triangles is they bear anywhere but at the pitch line if the angle is off, and it makes no difference which way. I guess for me, the pitch diameter is a specific theoretical size based on the particular thread - so that if the form is off, the wires will be measuring at *some* pitch diameter - just the wrong one. Yeah, I think that's more what I had intended to say. The pitch line is wire diameter critical, so altering the form would have some minor effect on the true (desired theoretical) pitch line, although it would still be very close, certainly closer than a triangle that would bear either at the major or the minor diameter. The main idea is that the wire will be riding somewhere near the pitch line, which, obviously, thanks to form error, would not be proper. Not that it's any better, though. If anything is wrong, does it really matter which feature? Scrap is scrap. That's the reason we were never allowed to chase threads without the threading tool being inspected by QC with a comparator before making the setup. It was not uncommon to chase threads for a week at a time, and then repeat with a different part. All threads we generated were single pointed. There were no die heads in the facility, and that was by choice. Those of us that chased threads got very adept at doing so. Please keep in mind that this was years before insert tooling was available. Guys today would read this and wonder just what the hell I was talking about. In all my years in the missile industry, I never saw an insert threading tool, ever. What a far cry from today, where most CNC operators likely have no clue about sharpening a threading tool. Things change, not necessarily for the better! :-) I cherish my hand sharpening skills. Actually, thread gages pick up thread form error to some degree. Considering the no go is generally truncated, if a go gage fits, but the form is off, the no go is likely to go on as well, depending on the thread form angle. Other features may be off, so it won't go. Because the gage checks angle to some degree, when you finally get a thread to fit the gage that is off form, it is usually off so far in other features that the no go betrays the bad form. If you kick this around in your head a bit, I think you'll see what I'm talking about. Yes. I've seen this when single pointing threads with some error along the way - having the tool not set 90 deg to the work comes to mind. Or trying to fit a thread that was improperly cut to begin with as another example. Say if an ID thread has too large of a flat on the major diameter, or if the minor diameter has the threads too pointy (no flat). Then I've seen where the thread one is trying to single point to fit the part simply won't go unless it is either cut too far, but simply kissing the major diameter of the male thread will allow it to drop in nicely. Yep, I've seen that, too. These examples point out just how critical threads are, yet are treated as if they are insignificant by many. Threads, and gears, are almost an industry unto themselves. There's so much to learn and know that many never even scratch the surface. I've had some experience with threads, but know nothing about gears. I shudder to think now long it would take me to get up to speed with them. Ring gages, in particular, are very effective at determining many features, although they may not describe the degree of error that may exist. They actually check all major features, major diameter, pitch diameter and minor diameter, and by variations in how they fit, thread form. When a go gage fits well, but the no go does, too, you know something's amiss. All you have to do is determine what's wrong. There's nothing like having a comparator to help in working with threads when it's important that they be right. For me at home I'm typically trying to fit some existing part with my single pointed thread. So I simply use the part as the 'gage' in a rough sense. Of course that leads to the problem that at some time I wind up trying to fit to another part I've already made, and I wind up with my own private local NBS for threads. :^) Chuckle! That's one of the reasons I preach thread wires. If one is conscientious about grinding and setting the threading tool, you can work to known standards (P.D. from the charts) and get a good thread every time. You seldom stray far from interchangeability. Anyway I've always found that getting the tool ground to the correct angle, getting it set perpendicular to the work, turning the major diameter correctly, and then leaving a bit of the part undersized (to be removed afterwards) to the minor diameter, are a few of the best ways to get a decent threading job. I'll have to see about this wire stuff - sounds like a better way to go. Funny, I've used them as long as I've known how to thread (47 years now) and just assume others have had a similar experience in the course of their shop activities. The beautiful part about wires is that you have a complete inspection system, especially if you use pre-ground inserts for threading. Each wire size serves for any diameter thread with a like pitch, so even if purchasing the premium wires, which are expensive, your investment in gauging is minimal, yet of the utmost quality. Assuming you have the tool set up properly, and know about the proper major diameter (not always nominal), chasing a thread and sizing by wire will yield a proper thread automatically. For someone of your caliber, I think you'll enjoy using them, secure in the knowledge that you are no longer creating the "Jim Rozen" series of threads. On the other hand, maybe you'll miss the notoriety! g Give it a go, Jim, and give us your impressions of their use. Read my instructions of how to apply them. It works great, is very easy to do. Harold |
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A different single-point threading question....
jim rozen wrote:
For me at home I'm typically trying to fit some existing part with my single pointed thread. So I simply use the part as the 'gage' in a rough sense. Jim Yea this is my typical system as well . Not ideal yet still what I fall back on time and again Ken Cutt |
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A different single-point threading question....
Many years ago, right out of school, I worked at a gage shop in
Chicago grinding threaded plug gages. I measured pitch diameter all day using wires. We took a wire and wrapped sewing thread around one end and secured it with duco cement. Cut off about a foot of thread. Then tied all 3 wires together at the end of the foot long threads. The three wires were suspended over the work from a simple stand. We would check the gage pd using a supermicrometer. This set up made handling the wires very convenient. John Normile Guess I'm going to have to cut some music wire and make a holder. Otherwise this could be awkward with only two hands. :-) Any ideas on this holder? Ted |
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A different single-point threading question....
In article , Harold & Susan Vordos says...
For someone of your caliber, I think you'll enjoy using them, secure in the knowledge that you are no longer creating the "Jim Rozen" series of threads. On the other hand, maybe you'll miss the notoriety! g I was told a story once by a man who worked for Weston, the meter folks. He said that their operation pre-dated most of the standardized thread forms, going back before the turn of the century - and that they had their own in-plant thread standards which they supported with home-made gages of all sorts. Up until the late 70s they simply used their own standards and forms on all of the meters they manufactured. Amazing. Give it a go, Jim, and give us your impressions of their use. Read my instructions of how to apply them. It works great, is very easy to do. Hmm, lets see, first step is to get some copper wire of about the right size..... Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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A different single-point threading question....
"jim rozen" wrote in message ... In article , Harold & Susan Vordos says... For someone of your caliber, I think you'll enjoy using them, secure in the knowledge that you are no longer creating the "Jim Rozen" series of threads. On the other hand, maybe you'll miss the notoriety! g I was told a story once by a man who worked for Weston, the meter folks. He said that their operation pre-dated most of the standardized thread forms, going back before the turn of the century - and that they had their own in-plant thread standards which they supported with home-made gages of all sorts. Up until the late 70s they simply used their own standards and forms on all of the meters they manufactured. Amazing. Amazing, indeed! On the other hand, why not? Seems to me that thread standards are what they are only because everyone (?) agrees with standards set forth. Had Weston been aggressive in promoting their standards, maybe we'd have a completely different system today. Give it a go, Jim, and give us your impressions of their use. Read my instructions of how to apply them. It works great, is very easy to do. Hmm, lets see, first step is to get some copper wire of about the right size..... I've always favored #12 solid and a heavy hand on the mike. :-) Harold |
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A different single-point threading question....
"John Normile" wrote in message ... Many years ago, right out of school, I worked at a gage shop in Chicago grinding threaded plug gages. I measured pitch diameter all day using wires. We took a wire and wrapped sewing thread around one end and secured it with duco cement. Cut off about a foot of thread. Then tied all 3 wires together at the end of the foot long threads. The three wires were suspended over the work from a simple stand. We would check the gage pd using a supermicrometer. This set up made handling the wires very convenient. John Normile Of all systems I've ever seen or used, this one would be very acceptable. The thread would not influence the wires in any way, and you'd never lose them if you dropped them. Excellent suggestion in my opinion. Harold |
#34
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A different single-point threading question....
as a non-machinist I was having a hard time picturing this process. a quick search got this: http://www.precisiontwistdrill.com/t...h_diameter.asp which helped a lot..... |
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A different single-point threading question....
"Harold & Susan Vordos" wrote in message
... I've always favored #12 solid and a heavy hand on the mike. :-) So that's how they make thin triangular barstock... Tim -- "I have misplaced my pants." - Homer Simpson | Electronics, - - - - - - - - - - - - - - - - - - - - - - --+ Metalcasting and Games: http://webpages.charter.net/dawill/tmoranwms |
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A different single-point threading question....
"Tim Williams" wrote in message ... "Harold & Susan Vordos" wrote in message ... I've always favored #12 solid and a heavy hand on the mike. :-) So that's how they make thin triangular barstock... Tim Yeah, but with notches. :-) Harold |
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A different single-point threading question....
wrote in message news as a non-machinist I was having a hard time picturing this process. a quick search got this: http://www.precisiontwistdrill.com/t...h_diameter.asp which helped a lot..... Very cool site! It should help those that are confused on the issue. Thanks for the link! Harold |
#38
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A different single-point threading question....
Been wondering if I could get a fairly accurate depth of thread
measurment with only a single wire and a mic. ***************************** So I took a new 1/2" 13 bolt and miced it. The measurnent of the major diameter was .489" I miced it again with a .040" drill bit inserted in the thread. The measurnent was .496" In order to balance that reading I subtracted half the major diameter of the bolt (.496" - 489"/2) = .2515" and doubled the result .2515"*2 = ..503" So I now had the equivalent to a 3 wire reading. [IE .503"] So the sharp depth diameter reading would be 3 times the .040" drill diameter less or .503"- 3 * .040" = .383" The pitch diameter would be one pitch height greater or .383" + 1/13*.86603" = .4496" This .4496" pitch diameter falls nicely into the pitch diameter range of a class 3A thread. ****************************** Bill May seem complicated to do but you need no special kit, only two hands, and once you figure out the mechanics of it, it is easy and I would guess that the accuracy, while not as good as the proper three wires, it could serve most quite well. Bill (Hoping I didn't foul up my numbers) |
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A different single-point threading question....
On Wed, 2 Jun 2004 18:53:31 -0400, "Bill Darby"
wrote: Been wondering if I could get a fairly accurate depth of thread measurment with only a single wire and a mic. ***************************** So I took a new 1/2" 13 bolt and miced it. The measurnent of the major diameter was .489" I miced it again with a .040" drill bit inserted in the thread. The measurnent was .496" In order to balance that reading I subtracted half the major diameter of the bolt (.496" - 489"/2) = .2515" and doubled the result .2515"*2 = .503" So I now had the equivalent to a 3 wire reading. [IE .503"] So the sharp depth diameter reading would be 3 times the .040" drill diameter less or .503"- 3 * .040" = .383" The pitch diameter would be one pitch height greater or .383" + 1/13*.86603" = .4496" This .4496" pitch diameter falls nicely into the pitch diameter range of a class 3A thread. ****************************** Bill May seem complicated to do but you need no special kit, only two hands, and once you figure out the mechanics of it, it is easy and I would guess that the accuracy, while not as good as the proper three wires, it could serve most quite well. Bill (Hoping I didn't foul up my numbers) Of course, your one wire method only works if you first measure the OD of the part. And if doing several parts you must measure each part on the OD first. Unless your setup is good enough that the part to part variance is small enough that you can live with it. I hate thread wires. They are hard to hold on large diameter parts. And on coarse threads the wires may be so far apart that you are forced to use only one wire because the mike spindle is too small to bridge two wires.. And they don't check thread angle or minor diameter. And they are easy to lose in the chip pan. But I use 'em a lot anyway. ERS |
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A different single-point threading question....
"Eric R Snow" wrote in message news On Wed, 2 Jun 2004 18:53:31 -0400, "Bill Darby" wrote: Been wondering if I could get a fairly accurate depth of thread measurment with only a single wire and a mic. ***************************** So I took a new 1/2" 13 bolt and miced it. The measurnent of the major diameter was .489" I miced it again with a .040" drill bit inserted in the thread. The measurnent was .496" In order to balance that reading I subtracted half the major diameter of the bolt (.496" - 489"/2) = .2515" and doubled the result .2515"*2 = .503" So I now had the equivalent to a 3 wire reading. [IE .503"] So the sharp depth diameter reading would be 3 times the .040" drill diameter less or .503"- 3 * .040" = .383" The pitch diameter would be one pitch height greater or .383" + 1/13*.86603" = .4496" This .4496" pitch diameter falls nicely into the pitch diameter range of a class 3A thread. ****************************** Bill May seem complicated to do but you need no special kit, only two hands, and once you figure out the mechanics of it, it is easy and I would guess that the accuracy, while not as good as the proper three wires, it could serve most quite well. Bill (Hoping I didn't foul up my numbers) Of course, your one wire method only works if you first measure the OD of the part. And if doing several parts you must measure each part on the OD first. Unless your setup is good enough that the part to part variance is small enough that you can live with it. I hate thread wires. They are hard to hold on large diameter parts. And on coarse threads the wires may be so far apart that you are forced to use only one wire because the mike spindle is too small to bridge two wires.. And they don't check thread angle or minor diameter. And they are easy to lose in the chip pan. But I use 'em a lot anyway. ERS Yes Eric, this method, as far as I can see, will only work by first measuring the major diameter. It may work well if, as you suggest, part to part variance is small. In any case, I wasn't so much thinking of a production set up as I was a one of a kind deal where you are single point turning and you want to get a reading on how close you are to a specific fit. I personally have never tried the three wire system (don't have the wires) and was just doodling around trying to figure a way to do it with the things I have in the shop. PS I found that both my digital calipers and the mic could be used to get the same numbers. Bill |
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