Calibration of Micrometers - Can we put 2 gage blocks together?

#11
Ryan and Geoff,

I'm just the ISO Coordinator, but I can tell you that most of the micrometers don't need to be super accurate except possibly those used at final inspection.

We make powdered metal parts that need to me miked at several stages of the operation (mold, size), but mostly just to see that the parts are within tolerance.

We are a very small company and the parts we make are not terribly intricate (bearings, sleeves, etc.) although some p/m parts require much more sophisticed measuring devices. (I worked for 19 years at such a company before being hit my the great downsizing wave);)

We do have several flange micrometers, which I think is what Ryan was referring to, and I've been told they do use blocks to calibrate them because of the generous tolerance.

Thanks so much for everyone's input - we are being audited next week to the new TS standard and I'm really holding my breath and praying for a miracle!

Sue
 
Elsmar Forum Sponsor

Mike S.

Happy to be Alive
Trusted Information Resource
#12
I would guess that the vast majority of folks who use standard outside mics are happy with readings within +/- .0001" or +/- .0002" of the standard's value, otherwise they would be using something else for the measurement. I've used and calibrated such mics from several major manufacturers (with +/- .00005" or +/- .0001" mic resolution) for over a decade and never saw a calibration instruction from any manufacturer or user mentioning the use of a "monochromatic light and optical parallels" for parallelism or flatness verification. For most folks that is probably major overkill, IMO, unless the edges only of the anvils on the mics are often used, and even then I can think of easier/cheaper ways to test for practical parallelism/flatness issues unless it were a very unusual use situation. JMO.
 
R

Ryan Wilde

#13
Mike,

First off, without a light (about $150) and a set of parallels ($168), I could shoot holes in any calibration of a micrometer, especially at ±0.0001". If you measure anything spherical, smaller than the anvil contact area, or irregularly shaped, it comes into play. I've measured "calibrated" micrometer anvils at over 0.0005" that you would not find with a gage block. Every military procedure calls for it, as does the old MIL-STD, as does the new (if it is out yet) ANSI specification. I've now worked for 3 accredited labs as well as working in a government lab, and I've yet to meet an ISO 17025 assessor that would let a lab get away without the proper check.

But I will give you that there is an alternate method of proving parallelism. You will need two calibrated spheres (spherical within 10 µin) that are of differing size by 0.012-0.013, as well as a light and an optical flat.

Overkill? Possibly for a specific application, but as an external laboratory, I have to be able to prove that an instrument meets published specifications. Flatness and parallelism are part of those specifications.

That said, these methods are those accepted and written in every standard concerning micrometers that I've ever seen. A company can omit them, if they desire, but at that point the micrometer meets a "custom specification", and no longer meets either manufacturer's specification, ANSI specifications, MIL specifications, or any other mass published specifications.

A custom specification is often fine for a company's needs, but then you have the burden of proof that it is, in fact, adequate. Quite often, the proof is more expensive than the equipment to meet the specification.

Ryan
 
Last edited by a moderator:

Mike S.

Happy to be Alive
Trusted Information Resource
#14
Ryan,

Your points are well taken. As you suggest, you as a cal lab have different needs/requirements than most users. 99+% of the time we measure parts larger than the anvils, but I take a quick look at flatness/parallelism by using a small calibrated gage pin or gage block measured in different places on the anvil faces. Ideal, probably not, but suitable for my uses.

Can you point us to the procedure references you mentioned - MIL or ANSI?
 
K

Ken K

#15
I also understand where your coming from Ryan, but how many companies have tolerances of ±0.0001" on their micrometers?

Some of the products we measure have a thickness tolerance of
3mm +/-10%. Do you really expect me to calibrate our mic's and calipers to ±0.0001"? Hardly.

But then again, if you produce product with reall tight and critical tolerances then I would agree. But I also feel some companies spend foolishly when it comes to calibration services and pay for something that is not really needed.

We just went to outside calibration on equipment we used to calibrate in-house. As we are in the process of ISO 17025 accreditation, I didn't want the hassle of having to meet the calibration portion of the standard. They made a house call and did the stuff in-house. I sat there and wondered how they ever became accredited. Scary stuff!
 
R

Ryan Wilde

#16
Mike,

You can get the MIL at a very little-known site called ASSIST. It's free, and just about all of the MIL specs are there in PDF format. Go tohttp://assist2.daps.dla.mil/quicksearch/ and start looking for what you want. The one for micrometers GGG-C-105C. For flatness, it calls out either optical flats or a precision indicator with a precision reference plane (this is a very time-consuming, expensive option). For parallelism (they call it angular trueness) it calls out precision angles, feeler gages, and a precision square (a VERY expensive method, also time consuming) or autocollimator (about a $50,000 option).

The MIL specs are being replaced by ANSI specs in the US. I don't know if the micrometer spec is approved yet, but I saw a few versions of the draft. It is either ANSI/ASME B89.1.13 or ANSI/ASME B89.1.14. One was micrometers, the other was calipers, and for the life of me, I can't remember which was which. Anyway, the ANSI site is http://www.ansi.org . The problem is that all ANSI specs cost money, and are copyrighted.

There is also ISO 3611:1978, which is the international standard for micrometers, which I guess eventually we will all have to use for international trade agreements.

Oh, another site you might like to see is http://www.nssn.org , where you can look up the latest version of just about any specification worldwide.

Ryan
 
Thread starter Similar threads Forum Replies Date
Q Micrometers to Measure Coating Thickness - Failed Calibration Flatness & Parallelism General Measurement Device and Calibration Topics 9
M Writing a Calibration Procedure for Groove Micrometers General Measurement Device and Calibration Topics 4
R Self (In-House) Calibration of Measuring Tools (vernier, micrometers etc.) General Measurement Device and Calibration Topics 17
5 Calibration of Thread Pitch Micrometers General Measurement Device and Calibration Topics 3
D Calibration work instuctions - Micrometers, indicators, etc. showing the uncertainty Measurement Uncertainty (MU) 2
M Calibration Procedures for checking and certifying micrometers and calipers General Measurement Device and Calibration Topics 3
Marc Calibration Environment - Micrometers - NCSL RP 7 - Laboratory Design General Measurement Device and Calibration Topics 5
lanley liao Question regarding the calibration of monitoring and measure equipment. Oil and Gas Industry Standards and Regulations 0
N IATF Calibration Lean in Manufacturing and Service Industries 4
Q Do these certificates of calibration meet ISO 9001 requirements for traceability to NIST? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 11
T Plug Gage Calibration Calibration and Metrology Software and Hardware 1
M Load Cell Calibration using a totalizer on a flow meter General Measurement Device and Calibration Topics 0
E Calibration Records needed ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 1
D Limited Range Calibration - 5000 lb Industrial floor scale General Measurement Device and Calibration Topics 3
D Calibration of Small Scales General Measurement Device and Calibration Topics 26
C How to Establish the Calibration & Measurement Capability (CMC)? ISO 17025 related Discussions 1
I IQOQ or just initial calibration required? General Measurement Device and Calibration Topics 3
B Calibration in real life ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 3
J Calibration cycle for monitoring & measuring tools used in medical device manufacturing General Measurement Device and Calibration Topics 5
A Is calibration of test weight required General Measurement Device and Calibration Topics 4
S Calibration Frequency for Slip Gauge Kit used for CMM Calibration? General Measurement Device and Calibration Topics 0
S Calibration/Verification of customer fixtures IATF 16949 - Automotive Quality Systems Standard 6
Ron Rompen Calibration by manufacturer ISO 17025 related Discussions 4
Q Calibration verification records 7.1.5.2.1 IATF 16949 - Automotive Quality Systems Standard 2
B AS9100D 7.1.5.2 Calibration or Verification Method using outside cal lab AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 1
W Next Calibration Due Date Calibration Frequency (Interval) 5
S Where do l get calibration standards to run a calibration lab? Other ISO and International Standards and European Regulations 2
A OEM On-Site Calibration issues during Covid19 ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 12
D Calibration tolerance question using Pipettes Medical Device and FDA Regulations and Standards News 1
M Calibration Certificate Result issued by an accredited external laboratory General Measurement Device and Calibration Topics 9
G Calibration of "Master Parts" Used as Gauges Calibration Frequency (Interval) 5
R Calibration lab environmental monitoring General Measurement Device and Calibration Topics 4
G Calibration of Rotronic probe but not digital readout? General Measurement Device and Calibration Topics 3
F Standard Calibration Procedures: Recommended Practice ISO 17025 related Discussions 0
T Temperature Requirements For In House Calibration - AS9100 AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 16
B Gage calibration frequency, ISO and IATF - What are the requirements Calibration Frequency (Interval) 3
Crimpshrine13 Laboratory Scope - Calibration vs. Test Methods - IATF 16949 IATF 16949 - Automotive Quality Systems Standard 3
Crimpshrine13 Calibration of pH Meter Probe Calibration and Metrology Software and Hardware 3
F ESD workbench "calibration" Manufacturing and Related Processes 2
C Correct Calibration Method for Dial Depth Gage General Measurement Device and Calibration Topics 6
F Nist traceable calibration certificates General Measurement Device and Calibration Topics 1
G Tool tracebility and First calibration requirements for aerospace (AS9100) organisation AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 5
D Calibration of Digital thermometer with surface probe General Measurement Device and Calibration Topics 1
T Calibration or Verification -> Cm and Cmk, etc. Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 3
G Is repeatability required for equipment calibration? General Measurement Device and Calibration Topics 10
was named killer AS 9100D - Calibration Instructions - Controlled documents? AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 6
B Photovoltaic Tester Calibration General Measurement Device and Calibration Topics 0
B Temperature loop: partial calibration General Measurement Device and Calibration Topics 10
G Glass scale calibration at 74 degrees F? General Measurement Device and Calibration Topics 4
A Digital Timer Calibration Requirements General Measurement Device and Calibration Topics 3

Similar threads

Top Bottom