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HI LO Set Masters for Thread Rings - Calibration Procedure

#12
This is not covered in the B1.2.

The pitch diameter isn't really "different" per se. The lo is the min pitch diameter of the ring and the hi is the max.

So if you have a 1-8 2A thread ring- your P.D. is 0.9168-0.0004 on the Go. So your lo end on your hi-lo would be 0.9164 and your hi would be 0.9168. But if you look at the handle, or the shank of the member, it will list the P.D. of the go plug as 0.9168.

NoGo should be the same way. The thread ring is 0.9100 +0.0004 so your lo is 0.9100 and your hi is 0.9104, but the P.D. listed on the handle or shank would be 0.9100.
 
#13
Thank you for your response. If I want to measure a regular plug gage, for the GO, I will take the nominal pitch diameter (minimum pitch diameter of the internal thread) and add the gage tolerance to set my upper limit. If I want to measure my GO HI-LO plug gage, for the HI, I will take the nominal pitch diameter and add the gage tolerance to set my upper limit. What are the specifications for setting the LO tolerances? How do I determine what number to subtract from the HI nominal to get my LO nominal? In your example you subtract 0.0004 (then you will still need to add/subtract gage tolerances to set your upper and lower limits) but what about other sizes?
 
#14
You would need a copy of the B1.2 or B1.16 standard to get the tolerance. The 0.0004 that I used above is the is the tolerance band for that particular size thread ring.

Beyond that, the tolerance is ±0.000050 for the Lo portion and +0.0001 for the Hi.

So your dimensions altogether would be:

Go
Lo PD 0.9164 ±0.00005
Hi PD 0.9168 +0.0001
Truncated Major 0.9809 -0.0006
Full Major 0.9980 +0.0007

NoGo
Lo PD 0.9100 ±0.00005
Hi PD 0.9104 +0.0001
Truncated Major 0.9641 -0.0007
Full Major 0.9980 +0.0007
 
#15
You would need a copy of the B1.2 or B1.16 standard to get the tolerance. The 0.0004 that I used above is the is the tolerance band for that particular size thread ring.

Beyond that, the tolerance is ±0.000050 for the Lo portion and +0.0001 for the Hi.

So your dimensions altogether would be:

Go
Lo PD 0.9164 ±0.00005
Hi PD 0.9168 +0.0001
Truncated Major 0.9809 -0.0006
Full Major 0.9980 +0.0007

NoGo
Lo PD 0.9100 ±0.00005
Hi PD 0.9104 +0.0001
Truncated Major 0.9641 -0.0007
Full Major 0.9980 +0.0007
Thank you again for all of your help. Why us it that we add the 0.0001 to the hi and add/subtract half of that for the lo?
 
#16
Hi All,

PMC used to make unm hilo thread setting plug gages, but they don't make them anymore. They still make hilos but not the unm variety. These are used for setting adjustable unm ring gages. Does anyone know if adjustable unm ring gages exist?


Thank you,
Jo
 
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