Plug Gages and Pin Gages

[eliot15]

Just trying to get clear on the difference between plug gages and pin gages.

Pin gages come in the plus or minus variety. I get that. We have a minus set at work which is -.0002. So a nominal .5000 pin gage is really .4998. Right? We generally don't work in tenths on my job, 'cept when reaming and what not.

Plug gages I take it come in a go or no-go variety. Never used them. Are they just like pin gages, only with a niffty red and green holder? But what are the sizes of a go and a no-go plug gage? Are they also plus or mius or something? Are they the same length as pin gages?

[txcncman]

Most shops just use their pin gages as go/no go gages. You can buy the pretty little green/red handles separately. There are generally no "accepted sizes" of go/no go gages. It is entirely dependent on the part blueprint and the standard in force. Standards for hole clearances vary by standard and application and engineering call out.

[eliot15]

From a purchasing perspective, I'm finding the terminology confusing.

For example, the MSC on-line catalog lists:

"Plug & Pin Gages (Go/No Go Gages) & Accessories"

...but then they don't make any distinction between the two. They also list:

"Plug Gage Handles"

So as far as I can make out, plug gages and pin gages are the same thing. A pin gage just becomes a plug gage when you stick it in a plug gage handle.

If your shop is anything like ours, half of the pin gages you need to use all the time got lost a couple of years ago and are "on order". But there are plenty of ones you'll never use. So I thought I'd pick up a few I need all the time.

Also notice the ZZ and X grades seem to be the most popular. For my purposes, I imagine I could get away with the ZZ grade.

Thanks

[eliot15]

I just downloaded the Vermont Gage catalog. They break it down like this

Plain Plug Gages

-Class ZZ Standards

--Economical General Purpose Pin Gages

---Go (Plus) or NoGo ( Minus)

-Class X Standards

--Standard Class X Plug Gages

---Go (Plus) or No-Go (Minus) tolerance

There is no top level category called Plain Pin Gages, but the General Purpose Pin Gages are listed in the Plain Plug Gage category.

Then the ones with the handles are called Class ZZ and Class X assemblies.

So again pin and plug gages seem to be the same thing. Am Go = minus, and No-Go = +.

Confused yet...me either...

[txcncman]

I am going out on a limb and guessing you are pretty new to machining and pretty young too.

You are making a mountain out of a mole hill.

If you hole tolerance is 0.525 +0.003 / -0.000 you would select a 0.526 pin (the +/-0.0002 won't really matter) as the GO gage and select a 0.528 pin (the +/-0.0002 still won't really matter) as the NO GO gage.

[txcncman]

I want to add that I appreciate you taking time to sort this out for yourself. But you stopped a little too soon in your analysis, and not soon enough.

[eliot15]

Thanks

[fizzissist]

So as far as I can make out, plug gages and pin gages are the same thing. A pin gage just becomes a plug gage when you stick it in a plug gage handle.

If your shop is anything like ours, half of the pin gages you need to use all the time got lost a couple of years ago and are "on order". But there are plenty of ones you'll never use. So I thought I'd pick up a few I need all the time.

Careful here...... Just sticking a pin in a handle is fine IF....

YOU KEEP TRACK OF YOUR GAGES!!!

If you use a pin that's a +/- as a gage, you need to either mark the pin itself and note what it IS when using it. A pin is not a "gage". A gage is calibrated, and usually more accurate by an order of magnitude than your typical pin.

It's too easy to end up with scattered pins that you don't know if they're over or under, and today's customers won't be thrilled having to deal with time consuming QC issues.

Today's customers are going to be more demanding of your QC standards and documentation. Trust me. Don't take a casual approach to it if you want to compete.