Go / No Go Pins - Verification question

M

MEDQA

Hello -

I am seeking an educated confirmation that I understand the process of verifying go / No Go pins.

Using Class Z pins (+.0025mm / -.0025mm) as a reference.

A .250mm GO pin must be between .250 & .2525 (+.0025mm / - 0mm)?

A .250mm NO GO pin must be between .2475 & .250 (+0 / -.0025)?

A standard or master .250mm pin with bilateral tolerance must be between .2475 & .2525 (+.0025mm / .0025mm)?

I believe some of our verification / calibration records are wrong in that a GO pin and a NO-GO pin reference a bilateral tolerance when I believe they should be a shown above. The pins are measuring where correctly.

thank you
 
Jim Wynne

Jim Wynne

Leader
Admin
Re: Go / No Go Verification question

MEDQA said:
Hello -

I am seeking an educated confirmation that I understand the process of verifying go / No Go pins.

Using Class Z pins (+.0025mm / -.0025mm) as a reference.

A .250mm GO pin must be between .250 & .2525 (+.0025mm / - 0mm)?

A .250mm NO GO pin must be between .2475 & .250 (+0 / -.0025)?

A standard or master .250mm pin with bilateral tolerance must be between .2475 & .2525 (+.0025mm / .0025mm)?

I believe some of our verification / calibration records are wrong in that a GO pin and a NO-GO pin reference a bilateral tolerance when I believe they should be a shown above. The pins are measuring where correctly.

thank you
Click to expand...

In general, gage pins are sold as either "plus" or "minus" with regard to nominal size. A Class Z .250mm "plus" pin will be .2525mm, while a "minus" pin will be .2475mm. The primary reason for this is that if you are checking a hole with (for example) a lower tolerance limit of .250mm, a pin that's exactly sized at .250 won't fit if the hole is in fact at the low limit. This means parts that meet the specification will be rejected.
 
A

aliasJohnQ

And when checking the pin gages, check with a master micrometer within your company or have it checked by a knowledgable company.
When using a master mic, make sure it's a master=being capable of at least twice the measurement as you are seeking.
One company I was working at a few years ago, with several individuals involved, couldn't save their lives with just trying to grasp the concept of this including the Quality Manager. And this is a medical device company where you need to know what your doing!
 
M

MEDQA

Re: Go / No Go Verification question

Jim Wynne said:
In general, gage pins are sold as either "plus" or "minus" with regard to nominal size. A Class Z .250mm "plus" pin will be .2525mm, while a "minus" pin will be .2475mm. The primary reason for this is that if you are checking a hole with (for example) a lower tolerance limit of .250mm, a pin that's exactly sized at .250 won't fit if the hole is in fact at the low limit. This means parts that meet the specification will be rejected.
Click to expand...

So I am correct, what is recorded for the go or plus pin must be between .250 & .2525, not 2475 & .2525?
 
Jim Wynne

Jim Wynne

Leader
Admin
Re: Go / No Go Verification question

MEDQA said:
So I am correct, what is recorded for the go or plus pin must be between .250 & .2525, not 2475 & .2525?
Click to expand...

I don't know whether you're dealing with "plus" or "minus" pins, or what your company's requirements are. The tolerance or acceptability of a gage pin should be based on the tolerances of the things it's used to verify.
 
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