Gage Identification Methods in a Job Shop



I would like to clarify some methods we are using versus what I think we need to do.

We are a job shop using Swiss Style CNC Lathes. We frequently have jobs with +/- .0002. We use mics (plenty of varieties), calipers, ring gages, plug gages, pins, indicators, etc.

Right now, we have a "shift change over" form that each machinist completes at the beginning of his/her shift. One of the steps to follow on this form is to validate the accuracy of your mics against a .2500Z pin that everyone uses ONLY for this purpose. As for the plug gages, we have a laser comparator that checks the pitch and other dimensions of the threads in a matter of seconds, so we use that before a gage is used for any job. We do the same thing with plug gages in order to verify the accuracy of ring gages as well.

There is some discussion around the shop about how we should calibrate all tooling and gages at our shop. Some higher-ups just think you need to have a color sticker on the equipment that means it's within calibration. My issue with this is, they've said that you don't need to individually identify each micrometer set, caliper, etc. It seems to me you need to be able to identify each piece so you know when to calibrate that specific piece. Their belief is that if you calibrate every single mic at the same time, you're good to go. Although it does make some sense, it just doesn't seem kosher to me.

Ideally I would prefer to mark each device (MIC0001, MIC0002, CAL0001, CAL0002, etc.) I still like the color coding sticker option, but thought it might be a good idea to write the calibration expiration date inside the sticker. To me, this doesn't seem like a huge endeavor but would raise fewer auditors' eyebrows.

One thing we're focusing on is to keep this SIMPLE. We want an effective system, but we don't want to over think it and create unnecessary additional work.

As for pin gages, we use the infamous For Reference Only stickers since we have so many. Each machinist double checks the pins he/she is using, but it is not documented anywhere. Is this a problem? Do we need any pins to be identified as calibrated or can we just stick with the FRO approach? We could easily use the laser comparator to check the accuracy of the pins, but that would take quite some time given the quantity we have. I don't want to spend all that time calibrating each pin, since not every pin is used regularly, if at any point during the calibrated time period.

I'm looking for any thoughts about the system we're using vs the system I envision. If anyone would care to share their system I would appreciate that as well. Thanks for your help!


Quite Involved in Discussions
Re: Gage Identification

"For Reference Only" is not the best term to use. I prefer Reference Artifact, Reference Standard, Working Standard, etc.
The metrology ID scheme is up to you. Any numeric or alpha-numeric that works for you. Just be consistent. Remember, the longer the ID, the more room you'll need on the calibration tag.
Speaking of which, it seems you don't have a standard metrology quality system in place. One of the requirements is for all calibrated tools/instruments to have a unique identifier, date calibrated, date due(sometimes), cal tech ID.
Even though calibrated, equipment suffers all kinds of abuse throughout the calibration cycle, so having a check standard to use more frequently as you do is a good idea.


Re: Gage Identification

I set up the calibration system at the machine shop I am presently employed at. Each instrument has a number assigned to it and that is both etched, if possible, on it and it is written on a commercially available calibration label. The label also shows when the instrument was calibrated when it is next due and who did it. I don't use labels for anything which we have calibrated from an outside supplier. All of this information is kept in a commercially available software package which tracks dates and all other information about the instrument.
I have included both company owned instruments and because this is the machining industry employee owned instruments. It's a lot to keep track of but if its kept up its doable and is necessary for this industry.


Trusted Information Resource
The problem with calibrating all the gages at the same time is over time they are not all calibrated at the same time. What happens when a gage gets run over? Or you get a new gage? By individualizing each gage, you may be able to extend some calibration requirements based on their lack of use. Use software to track.

As for the pins, we put them on a several year schedule to send out for calibration. We then "calibrate" each use.


dgriffith, I am in the process of creating a compliant system, so you're right, we're not meeting requirements as of now. I'm giving myself a max of four weeks to do get this squared away, but I'm hoping to have it done in three or less.

Walnut, thanks for describing your system. It sounds like the approach we may be taking. One issue we will have is that we use oil coolant in our machines, which means we have oil all over EVERYTHING in the shop. I'm trying to avoid using adhesive labels because most everything we've tried to stick to anything has fallen off rather quickly. If I were to use a sticker I would have an almost daily project of checking each piece of equipment to ensure everything was good to go. Obviously that wouldn't work. Having something tied to each gage wouldn't work either. Would you be able to tell me the name of the label you use? I may be able to contact them about this issue.

Golfman25, thanks for your input too. I thought that might save some hassle, but now see that it would be creating much more work for me over time.

If I label (etch or laser engrave) each metrology tool, could I just keep a list of calibrated equipment with the appropriate info in other columns (date calibrated, due date, by whom, etc) in a highly visible place? That way I don't have to worry about having labels and anyone can quickly verify that their tool is okay to use. Meets the simple aspect I'm seeking, but will it fly with ISO 9001?


The labels I happen to use are from SPI and are purchased through a distributor. We use coolant also in all the CNC machines and I've found that if I cover the SPI label with a piece of clear desk tape it stays on pretty good and stays readable.
If you etch the tool with a number and have it traceable in a database to when it was calibrated by who and when due I think that will meet all of the ISO requirements. Maybe one of the CB auditors that hang out here can correct me if I'm wrong.
The key to the system is to keep it up as you add new equipment and dispose of old and set a reasonable calibration interval to begin with. You can always change it if you have data to justify it.


The gage pins in my shop are all "Verify Before Each Use," and there is a work instruction that defines tolerance limits for them upon each verification. We don't really log the result; if the pin is bad, the user brings it to the lab, where it is discarded and a new one issued/ordered.

Unless, of course, they are part of a go/no go assembly, and all of those are identified by their drawing number (A-0001, A-0002, etc) along with any other gages, and are calibrated on an interval determined mostly by their usage (3 to 12 months, generally). Even standard sized thread plug gages have drawings in the files, and are identified by those numbers. The gage number is written on the label, and where possible, etched into the gage itself.

SMTE is tracked by the manufacturer's serial number, and I simply asked the people who order equipment to only buy from companies that serialize their products. Most everything gets the SPI sticker, covered by a piece of tape where required to keep it from falling off. We may be moving toward printing calibration labels through Gagetrak, in order to prevent transcription errors and people complaining about my handwriting abilities (or lack thereof). Brother makes a special extra-adhesive label specifically for harsh/dirty environments, which is what I'll be using, so if it happens soon, I'll let you know how that works out


Quite Involved in Discussions
All of our company tools are etched, (many from as far back as the 70's, before serial numbers), employee tools are also etched when possible, (letter "E" then last four of their employee number). Tools that have them, manufacturer, model, and serial numbers are maintained.

Stickers with clear tape are placed on all tools, or if tool is too small or a large set (i.e.: gage blocks), on its case. Each year I get about five books of multi-colored stickers, (one color per page) and separate the pages so I can use the colors in sequence so I can also tell visually when they are due.

Long before I got here, someone got a software program to track all calibrations; unfortunately the program does not allow me to see history beyond the last calibration entry. So I am starting to use a spreadsheet for each tool that I calibrate, to track each calibration and deviations. I know, this is tedious, but company is migrating to WIN7 and we will lose our current software and they are looking at a vendor?s cloud-based system, will probably lose it all anyway.

The QA table in the shop has a 1-12? Caliper Master (tree) and a .5?-11.5? Depth Master, these are calibrated annually by an outside lab. Machinist?s use these to check their tools prior to use. I have another set in my Cal-room that I use to calibrate tools.

It seems to work for now and we have gotten through a number of ISO Audits. I am also the ISO Management Rep. and lead auditor.



Involved In Discussions
Maybe I am to late to reply to this but here is the system we use in our shop. We have the Uni-Point system which electronically keeps records of all our calibrations. It informs you when an item is coming up for calibration or is past due. Each of our micrometers are labeled with a calibration sticker which tells us the micrometer number, example M-1, M-2, M-3 and so on, as well as the date it was last calibrated and when it is due next. Same goes for our calipers as well. Our system monitors all measuring devices including ring gauges, right up to the testing equipment, like the Rockwell tester. It also has a place to store scanned certificates from outside calibration vendors. Hope this helps and I'm not just repeating what someone else has said. :D
Top Bottom