Gage pin calibration procedure for accurately calibrating gage pins

  • Thread starter Coleman Donnelly
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C

Coleman Donnelly

#1
Could someone please point me to a comprehensive procedure for accurately calibrating gage pins to a specific standard?

TIA
 
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Jen Kirley

Quality and Auditing Expert
Staff member
Admin
#2
Re: Gage pin calibration procedure

I wonder why you need a specific procedure for that? Pin gages have a good deal in common with gage blocks and ring gages, as calibration checks go.

In any case, I did a search in the Post Attachments List (see the green button in the web page header) and found this list for you to peruse.
 
C

Coleman Donnelly

#3
Re: Gage pin calibration procedure

I am trying to determine if it is necessarry for us to calibrate using a super mic and why.
Thanks for your response!
 
J

jfgunn

#5
Re: Gage pin calibration procedure

The national standard for calibration of plug gages is the following:

ASME B89.1.5-1998
Sections 4.5.1, 4.8, 6.1, 6.2, Table 3

Note that two of the above sections talk about calibration by a noncontact method (ie laser micrometer) and the other talks about the method you would use with a bench micrometer.

You can purchase this document from www.asme.org.

Note that table 3 gives the specifiction for different calsses of plug gages. There is another paragraph that talks about plug gages that are class ZZ which is most likely what you have since you referred to them as "pin gages" .

In general, when people talk about pin gages, they are talking about the sets which are mostly class zz thiough class z are getting to be more popular.

Table 3 gives you all of the specifications based upon class.

For class zz pins tolerance is typicall +0/-0.0002" or +0.0002"/-0.

Wether you need a bench mic ior not depends on your needs for accuracy. If you sent these to me (which you could do since I am in Cleveland as well), I would use a laser micrometer whose accuray is +/- 30uin and the calibration would have a total uncertainty of about +/-70uin. If you required better accuracy, I would use somehting different to getthe uncertainty down to about 7uin (you can get 10 times the accuracy for about 5 times the cost). Note that if I didn't have the laser micrometer, I would use a bench micrometer for ZZ pins.

At a minimum, you should use about 4:1, so if the accuracy of the pins is 200uin, you should use an instrument accurate to about 50uin. Don't confuse the accuracy of the gage you might use with the resolution orf that gage. You can get a digital micrometer to show this many digits, but it really is not that accurate.

I hope this helps some.
 

bobdoering

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#6
Re: Gage pin calibration procedure

Don't confuse the accuracy of the gage you might use with the resolution of that gage. You can get a digital micrometer to show this many digits, but it really is not that accurate.
Absolutely true!


Also make sure you check along the length of the pin, and around the pin. Pins can get burrs or wear near the edge that will give false readings. There is a roundness issue that needs verified, too. You need to be certain that the entire working area of the pin falls within tolerance - or depending on the feature you are measuring, you can get false readings. Do not just check on diameter at one end and another at the other end and call it quits. That is not calibration! :cool:
 
C

Coleman Donnelly

#8
Re: Gage pin calibration procedure

. Do not just check on diameter at one end and another at the other end and call it quits. That is not calibration! :cool:
This is more along the lines of what i was looking for... I have heard many different opinions about how to calibrate a pin/plug gage. I have heard everything from checking it at one location with a set of mics to needing a bench/laser mic and cheking 3 locations at 3 different rotations. Now I am hearing about the importance of roundness and length (all of which makes more sense) so i feel the need to further explaing myself and my situation so that all of you can give me the "best" advice for my situation...

We are a TS16949 production company. We would like to at some point be able to do external work within the internal quality lab that this standard acredits us to. I am working toward improving good practice within the lab to compliance to the ISO 17025 standard but that is a long term and distant goal... We currently calibrate are gage pins / plug gages using a set of micrometers that is accurate to +/-o.oo1". Are tightest tollerance that these gage pins would be used for "in production" is +/- 0.005" - This means we would satisfy a 4:1 but not a 10:1 which would increase our overall uncertainty (I think). I am trying to justify the cost of a super mic / laser mic or whatever else would be best by showing the cost of sending out the gage pins every year for calibration vs. buying the equipment to do it myself. The problem is i can not find proof that could be shown to management that a super mic is even necessarry. That is the reason for my original post.

Thankyou for all of the input so far!
 

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
#9
Re: Gage pin calibration procedure

I have never been a fan of micrometers, just based on gage pressure. With calibration, I am even more leery of their limitations. I like Laser because of their non-contact. They are also fast and require less fixturing to measure correctly. The laser beam is a narrower area then a micrometer anvil. Micrometer anvils tend to give MMC, and making them smaller to reduce that impact increase gage pressure and potential for wear. Plus, it is not the discrimination but the statistical discrimination that you need to consider for 4:1 (based on gage R&R because of measurement error). But, you are thinking correctly that you do not need to calibrate to the stated gage tolerance if you do not intend to use them to that tolerance in practice. But, you need to protect users from using a gage calibrated to a lesser standard to be used to the original standard.

You may need to use something like a Mitutoyo Dial Snap Meters - Series 523. These control gage pressure and read to .00005". It may be a reasonable compromise with the big pens if they will not swing for a laser. Get a stand with it, though. Maybe go with the digital version.

The calibration of the micrometer used to calibrate the pins needs to be meticulous - flatness and parallelism of the anvils needs to be analyzed and determined to be statistically insignificant to your pin measurement.

Hope that gives more to ponder. :cool:
 

Jen Kirley

Quality and Auditing Expert
Staff member
Admin
#10
Re: Gage pin calibration procedure

When I was doing calibrations of any kind, or even inspections for that matter, the rule of thumb was that sensitivity in the gage used to perform the test would be 10X that of the item being tested.

That means your micrometer, if it reads in thousandths, is capable to inspect to a tolerance in hundredths. But a gage pin's tolerance is much finer! Indeed, when I used gage pins they were commercially bought and it was decided the only reliable, cost effective approach would be to replace them when their identification writing had rubbed off from the wear in use.

It sounds to me like your company needs more information before deciding to take on something like this. Might I recommend a class like QC Inspection Services offers? I am not affiliated with QC Inspection services.
 
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