I'M TRYING TO FIND HOW TO HOOK UP MY GAGES TO MY CAR. I BOUGHT MY GAGES AT A YARD SALE AND IT HAD NOTHING TELLING ME WHAT WIRE IS WHAT. "CAN YOU HELP ME.!!!!!
I work at a calibration Lab. We have found this "expanding thread gages" is not new to us. We have experienced that one manufacturer in particular runs most thread plug gages +.00025" to +.00035" over the tolerance on 50-60% of the gages we have seen. There are many manufacturers of thread gages and not all of them make gages to the tolerances i.e. 2B or 3B. What you have to know is does the manufacturer use his uncertainty in his manufacturing acceptance. If so, if they use an older model Supermic with .0001" graduations and their uncertainty is .0001" you can be +.0002" over the max and they may still consider this OK. Also the cal lab you used may do the same thing.
No one has mentioned the visual and cleaning aspects of this. I always view a suspect thread gage under a powerfull microscope. I also use an ultrasonic cleaner with alcohol and them throughly wipe all threads with a kimwipe and alcohol by hand until very clean. What I usually see is dings, scored thread flanks, and sometimes foreign material imbedded in the steel of the gage. All these can slso cause oversize readings of pitch dia.
easyr,
If you wish you can mail me one of your out of tolerance gages and I will compare the readings with the measurements I take. I am not a commercial calibration house but all of my instruments are certified and traceable to NIST. Email me and I will give you the address if you choose to accept. But I will have to send it back to you on your account#.
Hi Mike,
Thanks for the reply and offer. Unfortunately I authorized them to replace the rejected member. I could just change labs, but how would I ever know that this a just a very good lab and are doing it correctly while the other labs maybe just rushing the cal or using a less accurate method. I guess for now I will just err on the side of caution and replace the rejected members since it is only 3 gages out of about 200
Having calibrated my own thread plug gages and those of others (I used to work in a calibration lab), I have seen these gages grow. Normally it was caused by corrision or built up material on the threads (steel gage used on aluminum threads). When I calibrated a gage, either mine or someone else's, if I had a gage to "grow", whether it was a thread plug or cylindrical plug, I always double checked my entire setup/process and performed a visual inspection of the gage. I am not confirming the results from the new calibration lab, but I am confirming that this can happen. If I were you, I would send one or two of these "growing" gages to a third lab, don't use the original lab and see what kind of results you get with them.
One other thing to look at is the equipment used by each lab to perform the calibration. I have used a Pratt & Whitney Supermicrometer and a Labmaster. With the tolerances for thread plugs, I have seen some labs use digital micrometers. The difference in measurement uncertainties may the culprit.
Thanks for the reply Ramona,
They tell me that they also use a P&W Supermic. They tell me that they clean each gage and let the gage acclimate to their environmemt for 48 hours prior to cal. We manufacture Teflon parts which is actually a solid lubricant and will not abrade gages. It would be easy just to use a different lab but how would I ever know that this lab is maybe just a really accurate lab and the other guys are rushing through the cal?. Maybe for now I will just accept their results and replace the gages.
This is interesting, I just received ANSI B1.2 and in process of certifying all of our thread gages. We use the 3 wire method and a supermic for determining PD and of course the supermic for determining the MD (major Diameter). I have found out that some of the 2B thread gages are out of spec on the high end using the X tolerances. When you find an answer to this, I would like to know. I haven’t written any out of tolerance reports as of yet until I investigate further.
I just saw Mike's question and it made me remember something very important to the calibration of thread plugs. You must make sure that you are using the correct measuring force when using the 3-wire method. Using the wrong measuring force will give an incorrect measurement for that size thread. The measuring force is determined by the pitch of the thread and can be found in Table B2, page 176, of ASNI B1.2-1983.
Also, I am assuming that none of the gages are for pipe threads. That is a whole different ballgame, not to mention another standard. LOL
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Comments
scott125 7/13/2005
I work at a calibration Lab. We have found this "expanding thread gages" is not new to us. We have experienced that one manufacturer in particular runs most thread plug gages +.00025" to +.00035" over the tolerance on 50-60% of the gages we have seen. There are many manufacturers of thread gages and not all of them make gages to the tolerances i.e. 2B or 3B. What you have to know is does the manufacturer use his uncertainty in his manufacturing acceptance. If so, if they use an older model Supermic with .0001" graduations and their uncertainty is .0001" you can be +.0002" over the max and they may still consider this OK. Also the cal lab you used may do the same thing.
rsternberg 6/6/2005
No one has mentioned the visual and cleaning aspects of this. I always view a suspect thread gage under a powerfull microscope. I also use an ultrasonic cleaner with alcohol and them throughly wipe all threads with a kimwipe and alcohol by hand until very clean. What I usually see is dings, scored thread flanks, and sometimes foreign material imbedded in the steel of the gage. All these can slso cause oversize readings of pitch dia.
mike.brandon 6/1/2005
easyr,
If you wish you can mail me one of your out of tolerance gages and I will compare the readings with the measurements I take. I am not a commercial calibration house but all of my instruments are certified and traceable to NIST. Email me and I will give you the address if you choose to accept. But I will have to send it back to you on your account#.
easyr 6/2/2005
Hi Mike,
Thanks for the reply and offer. Unfortunately I authorized them to replace the rejected member. I could just change labs, but how would I ever know that this a just a very good lab and are doing it correctly while the other labs maybe just rushing the cal or using a less accurate method. I guess for now I will just err on the side of caution and replace the rejected members since it is only 3 gages out of about 200
Thanks again for your help and kind offer
rcade 6/1/2005
Having calibrated my own thread plug gages and those of others (I used to work in a calibration lab), I have seen these gages grow. Normally it was caused by corrision or built up material on the threads (steel gage used on aluminum threads). When I calibrated a gage, either mine or someone else's, if I had a gage to "grow", whether it was a thread plug or cylindrical plug, I always double checked my entire setup/process and performed a visual inspection of the gage. I am not confirming the results from the new calibration lab, but I am confirming that this can happen. If I were you, I would send one or two of these "growing" gages to a third lab, don't use the original lab and see what kind of results you get with them.
One other thing to look at is the equipment used by each lab to perform the calibration. I have used a Pratt & Whitney Supermicrometer and a Labmaster. With the tolerances for thread plugs, I have seen some labs use digital micrometers. The difference in measurement uncertainties may the culprit.
Hope this is helpful.
Ramona
easyr 6/2/2005
Thanks for the reply Ramona,
They tell me that they also use a P&W Supermic. They tell me that they clean each gage and let the gage acclimate to their environmemt for 48 hours prior to cal. We manufacture Teflon parts which is actually a solid lubricant and will not abrade gages. It would be easy just to use a different lab but how would I ever know that this lab is maybe just a really accurate lab and the other guys are rushing through the cal?. Maybe for now I will just accept their results and replace the gages.
Thanks again
mike.brandon 6/1/2005
This is interesting, I just received ANSI B1.2 and in process of certifying all of our thread gages. We use the 3 wire method and a supermic for determining PD and of course the supermic for determining the MD (major Diameter). I have found out that some of the 2B thread gages are out of spec on the high end using the X tolerances. When you find an answer to this, I would like to know. I haven’t written any out of tolerance reports as of yet until I investigate further.
Mike
rcade 6/1/2005
I just saw Mike's question and it made me remember something very important to the calibration of thread plugs. You must make sure that you are using the correct measuring force when using the 3-wire method. Using the wrong measuring force will give an incorrect measurement for that size thread. The measuring force is determined by the pitch of the thread and can be found in Table B2, page 176, of ASNI B1.2-1983.
Also, I am assuming that none of the gages are for pipe threads. That is a whole different ballgame, not to mention another standard. LOL
Good Luck,
Ramona