Thread Ring Gages - Discrepancies - Is the manufacturer specification wrong?

P

pancho-2007

#1
Hopefully someone can explain this one in more detail. We have a supplier that makes our Antenna end plugs for us and they have a spec of 6.7945 - 6.9723 tolerance on an M7x1 size. However my Ring Gage M7x1.0 6g GO gage is 6.324. Why would there be such a discrepancey for the sizes? From what I can see all calibrated by an A2LA lab uses the 6.324 as the standard for GO tolerance. Is the manufacturer spec wrong??
 
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Hershal

Metrologist-Auditor
Staff member
Super Moderator
#2
Your accredited cal provider does not set the specs for the go/no-go, they only report the measurement.....and they rely on external sources for that requirement.....

It is possible the manufacturer made a mistake.....contacting them with the question may be the best first step.

Hope this helps.

Hershal
 
C

Cordon - 2007

#3
Found this in some old notes of mine, used to do incoming inspection.

-M7x1.0 6g 6.974/6.794 (.2745"/.267")
-go gage 6.324
-no go gage 6.212

Hope this helps!
 

Wayne

Gage Crib Worldwide
#4
pancho said:
We have a supplier that makes our Antenna end plugs for us and they have a spec of 6.7945 - 6.9723 tolerance on an M7x1 size. However my Ring Gage M7x1.0 6g GO gage is 6.324. Why would there be such a discrepancy for the sizes?
I think that you are talking apples and oranges.
The supplier specification of 6.7945/6.9723mm is most likely the major diameter.
Your M7x1.0 6g GO Ring Gage has a pitch diameter of 6.324mm.

What is the class-of-fit specified on the print?
What is the specified pitch diameter on the print?
What is the major diameter specified on the print?

For pitch diameter there are many choices allowed in the thread standard.
Allowance for the pitch diameter: e; f; g; or h
Grade for the pitch diameter: 3; 4; 5; 6; 7; 8; or 9

For major diameter there are a few less choices allowed in the thread standard.
Allowance for the major diameter: e; f; g; or h
Grade for the major diameter: 4; 6; or 8

Other than choices in the standard, major diameters are some times reduced for mechanical reasons by design engineering.

See below the thread specifications for the most common class-of-fit used in he USA, 6g.

Pitch diameter tolerances and other data for M7.000 X 1.000-6g external thread:
Allowance class is................................. g
Tolerance grade for pitch dia. is.............. 6
Tolerance grade for major dia. is.............. 6
Number of starts.................................. 1
Metric Inch
Pitch is......................... 1.000 0.03937

Major dia. is................from 6.974 0.27457
to 6.794 0.26748

Pitch dia. is................from 6.324 0.24898
to 6.212 0.24457

Allowance is....................... 0.026 0.00102
Major dia. tolerance is.......... 0.180 0.00709
Pitch dia. tolerance is.......... 0.112 0.00441
Best wire size is................. 0.57735 0.022730
Constant is....................... 0.86603 0.034096
Max. width of flat at minor dia.. 0.250 0.00984
Min. width of flat at minor dia.. 0.144 0.00567
Max. flat form minor dia......... 5.891 0.23193
Measurement over wires, go........ 7.19003 0.283072
Measurement over wires, no go.... 7.07803 0.278663
The helix angle is....................... 2.881
Or if you prefer 2 Degrees 52 Minutes 53 Seconds
Data generated by: http://www.ring-plug-thread-gages.com/catalogs/thread_check/software.htm
 
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