Calibration tolerances needed - Calipers, digital indicators, feeler gages, etc

[ozziegood]

Is there some master list out there that will tell me the tolerances of calipers, digital indicators, feeler gages, gage blocks, and gage pins?

Thakns, Marie

 

[Jim Wynne]

The manufacturers of those devices will provide specifications and tolerances, although those can be loosened in your applications if it makes good sense to do so.

 

[Miner]

Is there some master list out there that will tell me the tolerances of calipers, digital indicators, feeler gages, gage blocks, and gage pins?

Thakns, Marie

Do a web search on "gagemakers tolerance". This will give you the tolerances for plug and ring gages for each class (xxx, xx, x, y, z) of gage. Most of the sites also provide guidance on how to select the appropriate class based on the tolerance as well as how the tolerance is applied in the case of a GO or NO-GO gage.

Here is a tip to save external calibration expense: If you have a set of gage pins, class xx, but you really only need class y, specify calibration to class y. Most calibration services charge less for calibration to lower class gages. It also guards against replacing a gage that does not meet xx limits due to wear, but is functionally acceptable.

As pointed out above, the manufacturers are good sources as well as the GIDEP program sponsored by the government.

 

[Dave Dunn]

A rule of thumb for calipers, mics and other instruments with a graduated readout (i.e. digital, vernier scales, etc.) is they should be accurate to ± 1 graduation of their scale. For example, a caliper whose smallest increment of reading is .0005" should be accurate to ±.0005"

As the others have mentioned, you can downgrade your instruments by calibrating to looser tolerances, but they should be noted with their calibrated accuracy. The caliper above could be calibrated to ±.001" if it's not used for measurements that require finer reading, but it should not be used thereafter for finer measurements unless recalibrated and proven capable of doing the measurement accurately.

 

[Charles Wathen]

A rule of thumb for calipers, mics and other instruments with a graduated readout (i.e. digital, vernier scales, etc.) is they should be accurate to ± 1 graduation of their scale. For example, a caliper whose smallest increment of reading is .0005" should be accurate to ±.0005"

Your best bet would be to visist the mfg's web site for accuracy statements. The example above may not always be true since the last digit can toggle between .0005 to .0010. Here is an example for a Mitutoyo Digimatic Thickness Gage. The resolution is 0.00005, but the accuracy stated on Mitutoyo's site is ±.00012".