Why Do They Make Gage Pins Minus And Plus

[Ed ke6bnl]

Not sure why they make gage pin Minus and Plus. The kits seem to have them increments of .001 anyway.

 

[mmcmdl]

Accuracy . If a small bore has a 2 tenths tolerance , the kit with the .001 increments are useless .

 

[Ed ke6bnl]

so with the minus pin gage set lets say .250 labeled pin is really .2498 or so.

 

[mmcmdl]

I answered a question from a member . It wasn't a slam . If you take it as one , so be it .

To answer the question . Yes , if you had a tolerance of .250 +0 -.0002 , you would need a .2498 pin and a .2500 pin for no-go , go gages .

 

[P T Schram]

I've been machining for 40+ years and didn't know.

 

[Bill Gruby]

OK, let's take it easy here. Relax and take a deep breath.

"Billy G"

 

[P T Schram]

And, before I forget

KE6BNL DE WD9HRP

73

 

[RJSakowski]

If super accuracy is required, pin gages are available in .0001" increments. Minus pin gages normally found in sets can be anywhere between .0002" undersize to the nominal dimension and plus pin gages anywhere between nominal and .0002" oversize. Every pin that I have checked has been .0002" undersize or oversize but that is not a universal given.

If you really want to get in tight, both minus and plus pins would be desirable.If you were trying to verify a .2500" hole with pin gages that were exactly nominal, you would not be able to insert the .250" pin. All you could say was the hole was greater than .249" and less than .251". A .250" minus pin would enter a .250o" hole and a .250" plus pin would not. If I could only afford one set, I would get the minus pins.

 

[planeflyer21]

To answer the question . Yes , if you had a tolerance of .250 +0 -.0002 , you would need a .2498 pin and a .2500 pin for no-go , go gages .

Exactly right. We used them for go/no-go gauges on tight tolerances. IIRC on the holes we were making would the no-go ever go but we had to change cutter compensation (or replace the cutter) when the go would no-go.

 

[planeflyer21]

I'll add this: when you are checking 2 dozen of the same parts and one of your QC checks is a hole that is 0.032", that would be some tedious measuring all day if you didn't have gauge pins.