Inspecting Full Thread Depth with a Plug Gage

T

Thetree

Hello all,
What is the correct way to use a thread plug gage to inspect the depth of a threaded hole? One of my guys thinks you should check to the end of the plug gage because the truncated thread is basically replicating the same engagement length you would get with a threaded part with a chamfer on it. My inspector always puts the gage on the comparator to check the length of the plug gage from the start of the truncated thread. His reasoning is that the print calls for example ".88 min full thread" so you have to inspect from the start of a full thread. I can see both arguments as being reasonable but I was hoping for some guidance.
Thanks for any input you can offer. -Dan
 

Michael_M

Trusted Information Resource
Re: Inspecting full thread depth with plug gage

I always measure from the first thread. The 'lead' on the thread gage may or may not be the same depth as the chamfer and that would only count if you 'count turns' not use a comparator to measure overall length.
 
H

Hodgepodge

Re: Inspecting full thread depth with plug gage

Hello all,
...My inspector always puts the gage on the comparator to check the length of the plug gage from the start of the truncated thread. His reasoning is that the print calls for example ".88 min full thread" so you have to inspect from the start of a full thread. I can see both arguments as being reasonable but I was hoping for some guidance.
Thanks for any input you can offer. -Dan

If you do it this way you won't mistakenly accept a thread that is out of tolerance.
 
T

Thetree

Re: Inspecting full thread depth with plug gage

If you do it this way you won't mistakenly accept a thread that is out of tolerance.

We also get "max full thread" so that is not exactly the case.

Is there a written guideline anywhere that could be printed as a "gauging instruction" and posted in inspection or put into our quality manual that specifically spells out the proper way to use a plug gage to inspect a thread depth?

"two guys on this forum say it is the right way to do it" rarely goes over well.

Maybe we could check all the gages and etch them with the gage length to save a step? Do you guys do this or just check them every time?

Thanks, Dan
 
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