Exempt from Calibrating our Tape Measures and Micrometers

P

poprock7

Can I get away with saying we are exempt from calibrating our tape measures and micrometers due to the fact that we have a variance in our product from our supplier. a lil background. we use micrometers to check our thickness on our metal which will vary depending who we received it from, and as long as it is within a +- say 1/8 inch then its is ok. same thing goes for our cuts which we use our tape measures for as long as we cut to an 1/8 of an inch can we get away with saying we do not need to use a metal rule or gage to check our tape measures for accuracy.
 

BradM

Leader
Admin
Hi there! Welcome to the Cove!:bigwave:

I was interested in this line:
and as long as it is within a +- say 1/8 inch

To me, that is a specification. So if you never have calibration conducted on your instruments, how can you state with confidence that it is accurately measuring to 1/8 inch?

Now, how often you should have it verified/calibrated is another matter. If you have good data and haven't had problems, you can extend the due date.

Also, it could be possible to get some dimensional standards in-house, and verify the equipment yourself.

My thought is if the reading matters, then I would calibrate. :)
 

Ron Rompen

Trusted Information Resource
Without knowing what standard you are registered to it is difficult for anyone to give a completely correct answer. However, in my experience, there is no standard which does not require calibration of instruments which are used to verify/validate product quality.

As Brad correctly pointed out, however, your method and frequency of calibration are left up to you (in most cases). If you tolerance is ± 0.125", then you don't need to calibrate to .001",

An inexpensive 9pc set of gauge blocks (usually under $100) would be more than sufficient to do your calibration.
 
T

The Specialist

I agree with Brad and Ron.

I cannot see how the example you give provides exemption.

You will have to calibrate.
 
J

JustADude

You can't avoid what the ISO 9001 standard says. In scetion 7.6.a it says measuring equipment shall be calibrated or verified. You probably need to go along the "verified" trail. You should have a procedure for "Control of Measuring Equipment". In that procedure you need to talk about tolerances and what is allowed, based on customer requirements. You probably want to have one measurement standard, like a set of guage blocks, but possibly a good mmetal tape measure. That standard must be sent out to a calibration house for verification. In the beginning it would probably need to be sent out once a year. If it is graded as "acceptable as received" or some jargon like that, you can back off to once every two years as long as it continues to be "acceptable as received". You use this standard to verify your other measuring devices in-house per your procedure. Make sure to keep your standard put away so it is only used for verifying the other measurement devices. Make sure all devices have a tracking and recall number and you keep a recall list and record of how and when each device is verified.

I know it is a lot more trouble than doing nothing, but I don't think you want to do nothing. Even if your registrar allowed it, doing nothing might lead to people using measurement devices that are damaged or worn to the point that they can't read them. You don't want that.
 

harry

Trusted Information Resource
.............. long as it is within a +- say 1/8 inch then its is ok. ..............................

What do you do if it exceeds this limit/tolerance?

If you use this instrument to make an accept/reject decision, you'll need to calibrate it. However, if it is merely to satisfy yourself or to keep tab on the suppliers documented thickness (you can always go back to them to re-verify the thickness), then things are different.
 
P

poprock7

Harry you said something that interest me. We do receive documents stating the thickness and we are only varifying upon receiving that our material is what they have already stated it was. We are not using our measurements as statements of thickness but only for ourselfs.
 

BradM

Leader
Admin
Harry you said something that interest me. We do receive documents stating the thickness and we are only varifying upon receiving that our material is what they have already stated it was. We are not using our measurements as statements of thickness but only for ourselfs.

OK, I'll try an answer for your question. :D Then I will pose a question to you.:D

If the reading does not matter, then don't calibrate. So if what value your instruments give you upon acceptance doesn't matter, then no; no calibration required. However, if you have a purchase order or a material requirements specification, how can you accurately verify that the material fulfills those specifications?

Hence Harry's valid question (along with the others). How you are using the values from the instruments will help guide your decision process.

* I'm a calibration guy. I believe in it. :agree1: However, a calibration program needs to be managed, and things need to make sense. Instruments that aren't used/don't matter need to be done away with. That which is left, probably matters and needs to be verified. Now, what level of verification and how often, falls under the "manage" issue.

Now comes my question...and you don't have to answer; just wondering. Why don't you want to calibrate the instruments? Is it a financial thing? I ask because maybe if you let us know your reason, we might be able to provide some suggestions.:agree1:
 
P

poprock7

No its not a financial thing, we just wanted to make sure this is something that was neccesary before we go that path incase we didnt have to. The guys who use the micrometers think that they dont need to be calibrated and that they can be zeroed out to show they are correct, which I know doesnt meet ISO standards stating that it is measured against a reliable source such as an NIST gage. It seems to us that to have no grey area and do away with any questions the best route is to get the NIST gage blocks and call it a day.
 
P

poprock7

Next question... Where is a good place to purchase a nice NIST gage block set?
Also what kind of steel rule will I need to meet the standards for our tape measures?
 
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