Where I can find the grade requirement for an inspection plate

[Russ]

Does anyone know where I can find the grade requirement for an inspection plate used in a QS9000 shop? All of our granite plates are certified to Grade B however we have many steel plates that are used from time to time that really need calibrated. However, we are having trouble finding any shop who can calibrate them to Grade B which is the standard we have in our QMS. Anyone know where and if this is spelled out in QS9000?

[Sam]

Gaging is not specifically called out in the standard. However 4.11.2.a of QS states that "the supplier shall determine the measurements to be made and the accuracy rfequired, and . . . . .

It is up to you to select the equipment you need to do the job. Some people use a 10:1 rule some use as low as 4:1. The standatd for surface plates is GGG-P-463. Two plates are listed Gradw A Inspection grade & Grade B shop grade. If yours can not be calibrated to grade B then it may not be of much use.

[Russ]

Sam,

Thru exhaustive research I see where you are on this. We state we calibrate our inspection plates to Grade B. Since we need to spell out our specifications, can we seperate certain inspection routines from the rest, i.e. say we use plates calibrated to a custom Grade C for checking only concentricity? I think this would simplify most of my problems with this issue.

So simple yet so complicated

[Ryan Wilde]

GGG-P-463c is the Fed Std for Granite Surface Plates only, and does not apply for steel or cast iron surface plates. I can't recall what the Fed Std for metallic plates is off-hand, but I will look when I get home tonight. As I recall, the specification on non-granite plates was much looser.

That said, it is very difficult to find a company that can measure/resurface a metallic surface plate because it is not cost effective. The process of resurfacing them is very time consuming and very close to artistic. In the hundreds of locations that I have been in doing surface plates, all but one had marked their cast surface plates as "Reference Only" and replaced them with granite surface plates, due to the very well characterized elasticity modulus of granite, the availability of service, etc.

If you must keep the steel/cast iron plates, then you should spec them as you need them, and hope that they never require resurfacing. The only company I ran into that could resurface them used the same method that they used for mill surfaces, which was a hand scraping that took a few days labor. If you are looking for a company to do the plates, then a mill resurfacing company will probably be you best bet, although it may be difficult to find any that are accredited to provide that calibration.

Ryan