M4 nogo plug gage torque limits

[connick]

Hello everyone,

First timer here. My company is dealing with a supplier who believes that I, the incoming inspector, am forcing the no go side of my plug gage into some threaded holes. I use two fingers to turn the gage and I am by no means using a lot of force. For sanity's sake I'd like to measure the torque used, but I haven't been able to find torque specifications. Does anyone know of a torque standard for no go plug gages?

 

[MintJulep]

A No-Go plug gage should not enter a female threads more than three turns. ASME B1.2 simply states that the gage "should not be forced".

I'm a bit confused by the stated argument. A threaded feature deemed acceptable by forcing a No-Go gage into it is disadvantageous to the purchaser and advantageous to the supplier.

 

[connick]

I suppose I should have elaborated a little to mitigate confusion.

We are receiving parts from a supplier which has M4 threaded holes. When I check the holes with my no go gage some accept the gage well beyond three turns. As such, I deem the parts unacceptable.

The supplier believes that their process is just fine and that the reason my gage is being accepted in the holes is because I am forcing it in.

Obviously, I disagree with their analysis of the problem. I plan to measure/limit the torque applied to the gage, but I am looking for an industry standard that is more specific than simply stating the gage "should not be forced".

 

[MintJulep]

I doesn't exist, and you don't want to go there anyway.

You've rejected the parts and won't pay for them.

It's up to the supplier to convince you, in a way satisfactory to you, that the parts are good, or give you good parts.

ANY compromise on your part will ultimately result in you with a pile of bad parts.

 

[CoryPad]

Just to support what MintJulep has stated, here is what is stated in ISO 1502 IS0 general-purpose metric screw threads - Gauges and gauging:

The NOT GO screw plug gauge, when screwed by hand without using excessive force, may enter into both ends of the threaded part, but by not more than two turns of thread.

 

[TVP]

I looked through the various IFI (Industrial Fasteners Institute) publications, but did not find anything that provides any requirements on force, torque, etc. It sounds like this is a supplier problem, but if you are so inclined, allow their personnel to participate in the NOT GO procedure in your quality lab: lay out 10 or 20 or x parts for you to inspect and 10 or 20 or x parts from the same lot for them to inspect. Regardless of the exact number of rejected parts in your pile vs. theirs, as long as you reject some parts and they reject some parts, I would say that the entire lot is rejectable.

 

[connick]

Thank you all for the responses.

The supplier has come in already and we have both checked several pieces at the same time, but the parts had already been inspected once by me. In this case they found that their no go gage entered into the same holes as mine and agreed that those parts were rejectable.

Their most recent lot was inspected simultaneously by the supplier and I for the first time. None of the M4 holes on these parts accepted a no go gage. Naturally, I'm happy to accept this new lot, but I don't want them to send in parts with oversized holes in the future and claim that their process is perfect and my inspection is the cause for the defect. They often send parts that are missing holes, missing threads in holes and in one case there was a broken tap in a hole that was supposedly checked with both go and no go gages. I, on the other hand, am quite confident that I am not applying excessive force on the gage, but I can't really say that definitively.

It's unfortunate that there isn't some standard for the force applied on plug gages, as "excessive force" is an extremely subjective term.

Thank you all again.