How to use NoGo thread plug gage?

[bakerbj]

I would like to know the proper use of NoGo thread plug gages. My customer contacts aren't around today so I can't get the standard from them, it's not on the print, and I don't have it. That's some important information I need obviously.

The production manager believes the part can make up to 2 turns max onto the NoGo side and still be good. I don't buy it since the part only has 3 complete threads. (1.5 mm pitch)

 

[DennisP]

Our standard for No Go thread gages is that the gage can go no more than 3 turns. The information comes from Machinery's Handbook. Unfortunately, with only 3 threads, this creates something of a dilemma. Do you feel any drag after 3 turns? If it is a ring gage, are you sure the lead threads are not worn and the gage is set correctly using the proper set plug?

 

[bakerbj]

I'm only getting 1 - 1.25 turns on the NoGo side right now.(plug gage) Usually, we don't even get a half turn, but this shipment a taps I received seems to be cutting a little larger than the last few.

There's no drag on the go side at all. I'm having the gage checked for wear.

 

[DennisP]

In that case, I would consider the threads to be OK.

 

[MikeHalloran]

Now, you need a REALLY-WON'T-GO gage.

;-)



Mike Halloran
Pembroke Pines, FL, USA

 

[JR97]

bakerjb,

FED-STD-H28/6 paragraph 3.1.1:

Threads are acceptable when the HI thread plug gage is applied to the product internal thread if: (a) it does not enter, or if (b) all complete internal product threads can be entered, provided that a definite drag from contact with the product material results on or before the third turn of entry.

I would say it can go all three turns provided the gage doesn't bottom out in the hole and there is definite drag on the third turn.

JR97

 

[caseynick]

Here's another one

ANSI/ASME B1.2 paragraph 4.2.1 says
"NOT GO (HI) functional diameter is acceptable when the NOT GO (HI) thread plug gage applied to the product internal thread does not enter more than three complete turns. The gage should not be forced. Special requirements such as exceptionally thin or ductile material, small number of threads, etc., may nececssitate modification of this practice."

Not much help in this particular case, but there it is