GR&R Data from Caliper Measurements

[Tsutorus]

Hello!
I'm new to the board and want to get your opinion on a GR&R. I have a supplier that provided a GR&R in a PPAP that I'm questioning.
They have a part with a 100.8mm - 102.4mm range. It is measured with a caliper, and the GR&R is reflecting variances to a resolution of .01mm which I don't believe a caliper can achieve.
Do you believe they can get their resolution down that low?

Thanks,

Timothy

 

[howste]

Re: GR&R Data

Hi Tsutorus, and welcome to The Cove!

Calipers can come with a resolution of .01mm. They may not be very repeatable at tight tolerances though. How do the GR&R results look?

 

[David-D]

Re: GR&R Data

Those numbers seem pretty tight to me. My experience with good 6" or 8" calipers (Mitutoyo, etc) is that according to their Manufacturer's spec sheets they are accurate to 0.001" (.025 mm) and the digital ones have resolution to 0.0005" (which generally gives people a false sense of accuracy). I'm always very cautious of all the extra digits of resolution because they don't actually convey any additional accuracy.

Something seems strange with the numbers - perhaps they are reporting the resolution of the gage instead of the R&R results, perhaps the calculations are off (i'd request the data/calculations), or maybe they are using a micrometer (which I've sometimes heard of referred to as callipers - dont remember the country).

David

 

[Project Man]

My 0-6" Brown & Sharp digital calipers have a .01mm resolution. While we don't want to confuse resolution with accuracy, it is perfectly acceptable to use these calipers and document the entire readout for a GR&R.