ISO 6H Go Screw Plug Gauges Calibration to ANSI / B1.16M vs BS 3643

[Geoff Cotton]

ANSI / B1.16M vs BS 3643

Folks, can I have you URGENT help please.


We calibrate our M6 x 1.00mm ISO 6H Go Screw Plug Gauges to BS 3643 : part 2 :1981 and BS 919 part 3 : 1968.

i.e Pitch Dia 5.350mm, Tolerance +0.0065mm to +0.0175mm.

The reference on the Calibration Certificate forwarded to us by our supplier reads ANSI / B1.16M

Pitch Dia. 5.350mm +0.008mm

Does this match the American standard for 6mm screw plug gauges?


Thanks in advance.

 

[bobhall]

Standards for M6 X 1.0_6H thread plug gage is:

GO PD = 5.350 - 5.358
HI PD = 5.500 - 5.492

GO MAJOR = 6.00 - 6.013
HI MAJOR = 5.700 - 5.687

 

[Geoff Cotton]

Bob,

Thanks for the info.

Please enlighten me.... what does "Hi" refer to, is it somthing in the American standard?

 

[Wayne]

The reference on the Calibration Certificate forwarded to us by our supplier reads ANSI/B1.16M. Pitch Dia. 5.350mm +0.008mm. Does this match the American standard for 6mm screw plug gauges?

Yes, per ANSI B1.16M the pitch diameter tolerances and other data for M6.000 X 1.000-6H thread work plug gage are:
Allowance class is...................... H
Tolerance grade for pitch dia is.... 6
Tolerance grade for minor dia is.... 6
Number of starts....................... 1
Go major dia. is............. 6.000 + 0.013
Go pitch dia. is.............. 5.350 + 0.008
Not go major dia. is........ 5.700 - 0.013
Not go pitch dia. is......... 5.500 - 0.008
Allowance is............................. 0.000
Pitch dia. tolerance is................ 0.150
Best wire size is........................ 0.57735
Constant is.............................. 0.86603
Measurement over wires, go........ 6.21603
Measurement over wires, no go.... 6.36603
The projected half angle is......... 29.96 degrees
The helix angle is....................... 3.405
Or if you prefer: 3 Degrees 24 Minutes 17 Seconds
Data generated by: Thread Tech software

Standards for M6 X 1.0_6H thread plug gage is: GO PD = 5.350 - 5.358; HI PD = 5.500 - 5.492

Please enlighten me.... what does "Hi" refer to...?

While the GO gage is universally called ‘GO’, the NOGO gage has several popular designations. The NOGO plug gage is called: NO GO; NOT GO; and HI. The ‘HI’ is because the NOGO pitch diameter is larger than the GO. The NOGO ring gage is called: NO GO; NOT GO; and LO. The ‘LO’ is because the NOGO pitch diameter is smaller than the GO. I personally prefer ‘NOGO’.

 

[Wes Bucey]

FWIW
I just looked at my own personal stash of go/nogo ring and plug thread gages for straight threads - all read go/nogo from at least 3 different manufacturers.

 

[Wayne]

...the NOGO gage has several popular designations. ...I personally prefer...

...my own personal stash ... all read go/nogo from at least 3 different manufacturers.

To the point, the facts can be found documented in the standards. The nice part of these discussions is that it inspires me to search out the facts. The sad part is that ‘I personally prefer’ or ‘from my observation’ is sometimes flat out wrong. I spoke with an associate who sits on the B1 committee and received some historical data as well as the current requirements of the standards.

In 1947, when USA agreed to allow the metric system to be an authorized form of measurement in the USA, we also agreed to have our fasteners be interchangeable. In an effort to comply with this requirement, the current version of the ANSI B1.16M standard requires the NOGO thread ring gage to be identified as LO and NOGO thread plug gage to be identified as HI. In some previous version of the ANSI B1.16M standard the NOGO was required to be marked NOGO.

The reason for this relates to the tolerance convention of the gage members. The GO gages use identical tolerance convention wether ISO or ANSI; however; the NOGO gages are different. For the NOGO the ISO allows for a more liberal convention, which from a technical perspective could allow an out of tolerance part pass inspection, while the ANSI tolerance convention will pass only in tolerance parts. The discussion of the merits of the specific systems is beyond the scope of this thread.

The intention of the B1 committee was that if the gage was identified as HI or LO it would not have to be considered as a NOGO. What? That does not make sense! Well, yes it does after a fashion. The intention is that, if using the gage in the USA marketplace, the gage functions just like a gage made to ANSI B1.2. By this I mean the gage can be used as a NOGO and still inspect product that will always be compatible in both marketplaces. Where as, if using the gage under ISO requirements, and by modifying the usage procedure, it will operate acceptably. The modification to the usage procedure is that the gage is allowed to fully enter the product, but only with noticeable drag experienced after the second turn.

The marking of the NOGO gage for the Unified National Thread per ANSI B1.2 is a different story. There is not a constraint of complying with a 1947 agreement, yet the same discontinuity of the tolerance convention found in the metric series also exists in the UN series. A discussion of the differences can be found on the web. The marking requirements have changed over different revisions of the standard. The early method was to mark the NOGO gage NO GO, which was changed to HI or LO depending on plug or ring, and now the current revision requires NOT GO.

I suppose it may be a mark of the quality of the gage if the gage maker follows the minutia of the standard or not, but a quick survey of several gage makers found about half mark the NOGO as NOGO. As for myself, I still personally prefer NOGO.