Basis for Establishing Gage Tolerancing - "Gage Maker's Tolerances"

Can anyone tell me the basis for establishing gage tolerancing? Is there a national standard or is this left up to the company for their specific applications?

We use the standard "Gage Maker's Tolerances" for our plug gages and ring gages but other gaging such a go/nogo overall gage we use 10% of part tolerance from the control plan.

Also, do you have to write this in your calibration procedure?

Thank you
Kat.k.

Kat.k
I know for ring gauges US standard ANSI/ASME B89.1.6M can apply, I am sure a quick search of the ANSI web site will reveal more

Hi, Kat!

Some customers have explicit requirements for gage toleranes (GM, Ford, Navistar, et.al). It also depends on the whole gaging system and the discrimination required at the bounds of the process or product tolerance range. The 10% rule is an accepted rule of thumb.

Tolerances for both process and product have tightened in the competitive race for quality so much that some measuring systems cannot be used without reference to the original MIL-105 standard which allowed a master to use 25% of tolerance (ndc equivalent = 4). This is manifested routinely in the round-robin testing done by primary labs on gage blocks.

I hope this helps!

kat.k. said:

... Is there a national standard ... We use the standard "Gage Maker's Tolerances" for our plug gages and ring gages but other gaging such a go/nogo overall gage we use 10% of part tolerance from the control plan.

Click to expand...

It sounds like B89 is the place to look. B89.6 was given earlier and I know B89.5 also deals in the same topic. There may be more.

Just for fun; here is a 10% Tolerance Calculator.

kat.k. said:

Can anyone tell me the basis for establishing gage tolerancing? Is there a national standard or is this left up to the company for their specific applications?

We use the standard "Gage Maker's Tolerances" for our plug gages and ring gages but other gaging such a go/nogo overall gage we use 10% of part tolerance from the control plan.

Also, do you have to write this in your calibration procedure?

Thank you
Kat.k.

Click to expand...

This is actually a fairly broad question given the number of different types of gages out there.
To an extent it is going to depend on the company, what you make, who the customer is and so forth. Things like threads generally call out a tolerance spec on blue prints that goes to a standard for instance (0.50-13-2B) for an internal thread where the 2B is a specific thread tolerance and the gaging needs to reflect this.
Other dims or features may not be so specific.

For "homemade" gages, used strictly in house to check features, there is no reason that I know of that you can't set your own specs. Just be very careful in setting them so that you are certain you are taking into account all pertinant variables.
And - Yes I would say try to document these specs for the specific gage in your system.

Peace
James