CMM as Calibration Tool

[Underspec]

Curious if anyone out there is using your CMM for calibration. If so, can you list examples of what you calibrate? We are looking to use our new machine to help with calibrations.

[cmmguy]

All depends on tolerances of the gages and your CMM. Most likely fixture gaging would be the uses - like surface plate layout type of calibrations

[John Kingston]

It depends on a lot. What do you want to calibrate? What is the tolerance required for the gage?
I would NEVER use the CMM for calibrating gage blocks or ring gages. But I do use it to calibrate some of our fixtures that are used for part fit up. The tolerances on those are usually fairly liberal. (+/- .005 inch)

[Underspec]

I heard talk of gage blocks

[Rob_K]

We are calibrating longer Calipers ( 300 -1500mm), using 3-2-1 alignment set on Caliper

[rangerboat72]

I heard talk of gage blocks

No way. The CMM is not accurate enough. We only use our machine's for fixture or attribute gage (with large tolerance's) checks.

[#2#]

Well, it depends on what you use the gage blocks for doesn't it. I mean, if you use the gage blocks to calibrate something that only reads to two decimal places, a cmm would probably be good enough.

The only thing I've calibrated on ours is a 36 inch scale (overall length only).

They use it in drop testing units. They have to be dropped from 36 inches. We used to just have a steel bar but that wasn't good enough for an auditor. He said we needed something with markings so we could easily tell if someone cut off an inch or something - makes sense but wow is that being picky.

[Tested]

We use it a lot.
Any time the CMM is 10time better than the tolerance allowed I try to use the CMM.
The pwoers that be here continue to want me to layout fixture gauges to a gauge print; For the most part I refuse. Not only do the gauge print tolerances mean nothing to the actual part or part print. They also don't see the gauge the way the part will.

[cmmguy]

Well, it depends on what you use the gage blocks for doesn't it. I mean, if you use the gage blocks to calibrate something that only reads to two decimal places, a cmm would probably be good enough.

Classification of the blocks is more important than their use. Classification defines their possible use and that is what you calibrate to. I can't think of a any gage block standard - no matter how loose the tolerance - that would allow you to calibrate them on a cmm

[Matthew D. Hoedeman]

Classification of the blocks is more important than their use. Classification defines their possible use and that is what you calibrate to. I can't think of a any gage block standard - no matter how loose the tolerance - that would allow you to calibrate them on a cmm

Well, there are ways you CAN classify them and calibrate them on a CMM. First of all, it will depend on the actualy end use of the blocks.

Now, I KNOW that I am gonna get a ton of hate mail for this, BUT:

If you de-classify them, (no longer A, AA or AAA rated, or whatever they are) and state in your calibration paperwork that the acceptable tolerance for those gage blocks is, lets say, +/-0.0005", then you can do them with the CMM.

I AM NOT saying that this is acceptable to the original intent of the purpose of the gage blocks, BUT, if YOU can assign YOUR OWN acceptable limits, then yes, YOU can do it (waterboy)

[craiger_ny]

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Now, I KNOW that I am gonna get a ton of hate mail for this, BUT:
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I will spare you and send all of your hate mail to Paul instead. That way he can proof read it and forward it to you as appropriate.

[cmmguy]

Well, there are ways you CAN classify them and calibrate them on a CMM. First of all, it will depend on the actualy end use of the blocks.

Now, I KNOW that I am gonna get a ton of hate mail for this, BUT:

If you de-classify them, (no longer A, AA or AAA rated, or whatever they are) and state in your calibration paperwork that the acceptable tolerance for those gage blocks is, lets say, +/-0.0005", then you can do them with the CMM.

I AM NOT saying that this is acceptable to the original intent of the purpose of the gage blocks, BUT, if YOU can assign YOUR OWN acceptable limits, then yes, YOU can do it (waterboy)

Well, that is basically what I said... your thoughts arent incorrect, you just sort of finished the sentence. But there are other tolerances for flatness, surface finish, etc... that also would need to be declassified. Any gage can have its capability reduced - it just needs to be documented and identified.

[Hilton Roberts]

[QUOTE=Matthew D. Hoedeman;84677]Well, there are ways you CAN classify them and calibrate them on a CMM. First of all, it will depend on the actualy end use of the blocks.

We used to do a lot of that in Saint Louis. When gage blocks exceeded their size tolerance, they were moved into less accurate sets. Those blocks ended up as feeler gages for shop parts. Not the cleanest system in the world but we were able to do it.

[Steven69]

Curious if anyone out there is using your CMM for calibration. If so, can you list examples of what you calibrate? We are looking to use our new machine to help with calibrations.

I use the CMM to calibrate longer Venier calipers (yes, some people still use them), protractors, and holding fixtures for datum references. Simple gages with simple tolerances.

[Perry Fisher]

I calibrate attribute gages for metal stampings where applicable. Our tightest gage tolerance in ±.0002" on a small quantity of gages. Most of them are ±.0005" minimum.

Doing this I have greatly reduced the amount of manual data entry for gage calibration records. I shoot the CMM report to a .PDF file stored on the company server. If you start using your CMM for gage calibrations you can use that as a Continuous Improvement as well.