Zero part to part variation - Gage R&R project

Bev D

Heretical Statistician
Leader
Super Moderator
Do you not have access to automotive parts and their specifications?
 

Eng.Hamad

Registered
Brake rotors are precision machined on all dimensions. Digital calipers would be woefully inadequate to even begin to see the variation in the dimensions. This would be a resolution issue.
Hi Miner,
I am sure it is what you said, it is a resolution issue. The resolution of the digital caliper I have is 0.01 in! If I will use a digital caliper, I will need one with a higher resolution like 0.001 in.
Thank you,
 

Bev D

Heretical Statistician
Leader
Super Moderator
why is your instructor requiring automotive parts? if you do not work in automotive you aren't going to get the things you need to measure automotive parts. No automotive manufacturer is just going to give you a bunch of parts and the tolerances. Usually when teaching MSA the instructor will assign things that are commonly available and in large enough to volume to get you part to part variation.
 

Ron Rompen

Trusted Information Resource
Just to echo Miner's comments. A GRR of 100% states clearly that your measurement system is not appropriate for the feature you are measuring. 0 part-to-part variation tells you the same thing - a caliper cannot accurately discriminate a precision machined dimension like the one you are measuring.
One other tip - unless you have a HUGE tolerance, calipers are TERRIBLE at measuring inside diameters.
 

tmayur21

Registered
I come from a brake manufacturing company. Looks like you are trying to measure diameter of hub mounting surface with a vernier caliper.
It is an incorrect instrument to measure such a precision machined hole. Usually, such holes are measured by CMM or an inline measurement equipment like Renishaw Equator. If you still want to run Gage R&R on hub mounting holes of the rotor, you might want to get yourself a bore gage. Those are pretty expensive though.
 
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