Calibration of "Z" class ring gauges internally using a CMM

[Bob Gallinger - 2007]

Does anyone calibrate "Z" class ring gauges internally using a CMM ????
What other equipment should be used for calibrating rings.
"Z" class tolerance is +/- 0.0025mm (I believe)
Thanks

 

[sarasheed]

The question asked is not clear.
Do you want to check the ring gauges(Go & NoGo) manufactured to check the Shafts made as per ISO 286-2:1988 to" z" class tolerances.If so,the tolerances on Go and NOGO ring gauge will depend on size of the shaft and the Grade of tolerance to which the shaft has been made(Say Dia.20z6 ).

To check such ring gauges we use SIP-214 Universal Length Measuring Machine.An accurate CMM's like Zeiss UUM with automatic temparature compensation facility can also be used for this purpose.If the Ring Gauges are more of the same size,"Air Gauges "can be used for checking


Regards,
sarasheed

 

[Bob Gallinger - 2007]

I have about 15 ring gauges in-house. We use to have a Universal Measuring Machine (SIP) to calibrate these. The SIP has been sold and I'm left with finding out another method of measuring these gauges. I don't want to have these gauges sent out for external calibration every 5 years if I can measure them on my CMM. How do I prove to the auditor that my CMM is capable of measuring these class "Z" rings ?????
Thanks.

 

[qualitytrec]

My understanding is that you should be able to measure to within a tenth of the tolerance allowed for the item being measured. so take your tolerance on the rings divide it by ten and see if your CMM is at least that accurate. It has been awhile but I believe this is the case. Can anyone validate what I am saying or is the lid off of my white out again?

 

[CalRich]

Does anyone calibrate "Z" class ring gauges internally using a CMM ????
What other equipment should be used for calibrating rings.
"Z" class tolerance is +/- 0.0025mm (I believe)
Thanks

My understanding is that you should be able to measure to within a tenth of the tolerance allowed for the item being measured. so take your tolerance on the rings divide it by ten and see if your CMM is at least that accurate. It has been awhile but I believe this is the case. Can anyone validate what I am saying or is the lid off of my white out again?

Typically the 10:1 ratio is geared towards gage tolerance vs. part tolerance. For measuring gages, a 4:1 ratio between working gage and master is more the standard. Of course, if you can manage 10:1, that's even better.

We have a CMM that is accurate to only +/-.0051mm, so it would not be appropriate at all for measuring Z rings. (or any class, for that matter). For cylindrical rings, we use a universal measuring machine with some ID jaws that is accurate to about +/-.00025mm.

I would think that a simple bench mic would do the job. With only 15 rings calibrated every 5 years, I wouldn't invest too much $$ into it, unless you can find other items to calibrate with it as well (plain plugs, thread plugs, indicators). But if you just have the 15 rings calibrated every 5 years, I don't see why you wouldn't go to an accredited outside lab.

Keep in mind, too, that the .0025 is the Class Z tolerance only between .254mm and 20.95mm. The entire chart can be found here [.pdf]

 

[Bob Gallinger - 2007]

Thanks for your replies. I thought about the 4:1 ratio and my CMM won't be even close to accurate enough, no CMM could measure with that high degree of accuracy. I guess I'll have to get the rings externally calibrated.\
Thanks.