Calibration of Setting Rings, Measure Force on Vernier

There are companies set up that offer certification service such as Precision Metrology Inc. Their metrology rooms are held at constant temperature and humidity. If you want to go into this business, you need to contact them or the manufacturer of measuring instruments such as Starrett or Brown & Sharp and understand NIST Traceability standards. Visit www.NIST.gov.

Setting ring gages have standards for size, taper, roundness, surface finish and other parameters that take a variety of methods and tools to properly certify. To simply verify the diameter would take a minimum of a certified gage block set and a stable micrometer setup.

Typically vernier calipers are at best only accurate to plus or minus 1 thousandth of an inch. The operator typically uses 'feel' so that operator variation is usually a limiting factor. In a manufacturing situation, this can be measured by statistical analysis.

I hope this answers your question.

A laser mic will not have the capability to be used for calibration of your setting rings.

As suggested by the previous post, you should investigate periodic re-calibration using an external calibrated and traceable lab, or else purchase replacement "masters" when due for retirement. (Re-calibration can often cost more than replacement price and if a ring is found defective, you still pay for the test AND need to purchase a calibrated replacement anyhow.)

As for vernier forces, use R&R studies on the operators (for the precission and accuracy of verniers this should be adequate) and then based on those results determine whether operators and equipment are capable of making the measurements with the accuracy/precission you need.

You could use the calipers to "measure" a strain gauge and monitor the pressures applied by different operators.

Your best bet would be to have the rings calibrated by any metrology or cal. lab traceable back to NIST, as someone said earlier. They are capable of caling the rings to precision well beyond 1.8 microns (i'm guessing umm is supposed to be micron). I'm assuming you're asking why you can't just do it yourself. I think I can break a few things down for you. All things mankind measures physically can be traced backed to some standard somewhere. Most distance measurements have their roots in a platinum bar in france. It's a meter bar. For a while it was used to physically define a 'meter'. I believe now the term 'meter' is defined as a certain number of bands of light of a certain wavelength. But I digress. That said if you want to 'calibrate' something, your calibration method must be traceable back to some definition. Most of those definitions in some way go back to that platinum bar in france. You can imagine they don't just pull the 'ol bar out once a year and have a go with a ruler. It's a precise measurement done with instruments some of us can't even pronounce. All THAT said, you could just grab a calibrated mic and re'calibrate your rings. But the reality is that you're just checking your precision to an instrument that itself must be calibrated. It's kinda circular logic. "I calibrated this ruler to this stick which is calibrated to said ruler." Works great if your stick is the standard definition. Not so great if it's not (and yours ain't). Long story short save yourself the headache and pay a metrology lab 50 bucks a ring to have them calibrate it. They know what they're doing and it's a traceable standard. (and if you're balking at 50 bucks a ring, you're in the WAY wrong business)

I used slimline (Kaydon) ball-bearing rings to accurately measure small forces.

Load in one direction, deformation measured perpendicular to the load direction with a non-contacting capacitive probe and the other side slightly touching a hard stop or with a second capacitive probe.

Most laser micrometers do not have the resolution needed for very small deformations, capacitive probes are much better for this.

Calibration problem: a complete measurement arrangement would need an airbearing turntable or spindle (only very few ball-bearing spindles will have a sufficient accuracy), attached to the faceplate a linear (air- or ball-bearing) stage with good glass scales. The linear stage will have to carry a gage-block with two calibrated balls at the two faces of the gage-block or carry one bigger calibrated ball.

Going back and forth with the linear scale will provide the diameter, setting a new angular orientation after measuring one diameter will provide diameter as function of angular direction.

You can get this and similar arrangements made to custom order from Professional Instruments, Minneapolis, but I fear this may be pretty and costly.

You can get used equipment that suits your demands from lasermotion.com but integration will be likely your task

I have good experiences with both companies.

RHABE

Personally, I consider vernier calipers akin to guessing sticks (slide rules)..........if you use verniers for measurement, you are definitely not serious about accurate measurement. You would get a more accurate reading using spring calipers and appropriate micrometers, providing, of course you have the skills in using these instruments.

However, if you are serious about accuracy in measurement.........the greater the accuracy that you require, the greater the cost of the appropriate measuring equipment..........and of course, so does the cost of any manufactured component that requires this accuracy.