I have the same Mitutoyo digital calipers as mentioned above, had them for years (at least 3 batteries worth). When I was working in the aluminum extrusion business we did a Gauge R&R (Reliability and Repeatability) on all tools used for measuring, as per Six Sigma guidelines. You take 10 samples and 3 people. Each person measures each sample so, you have 30 samples (sometimes more samples/people). My digital calipers came in fine along with other dial ones so, I'll tend to disagree with your instructor. Ask him/her if they have heard of a Gauge R&R.
Working on aircraft, one of the most frustrating aspects when dealing with the suits upstairs concerned Gauge R&R.
Once a year, all our measuring tools had to be sent away. Every one of them in the shop. Tools that had been Dad's, My Uncle's (A tailor, so oddball stuff.) One's I'd had 30-40 years. One's I used daily.
I'm talking emotional attachments, here! lol!
Production stopped. Screw it. "I'm taking 10 days outa my O/T bank! Bye!"
I mean, c'mon. Upholstery. It's not like hydraulics, or sheet metal, jet engines, avionics.
Sure. Our tolerances were quantitative, but it's not like our exact measurements were written in stone. Dictated by a manual.
Our standard of perfection was the ability to replicate multiple examples, all exactly the same, by hand, from raw materials without a definitive guide as to the OEM's prescribed requirements or measurements.
We had a very wide margin of creativity.
When customer's would ask what it's gonna look like finished, it's not far from the truth when I tell them, "I dunno. I'm just making this **** up as I go along."
But as 'Interiors' also included the wood shop, our measurement devices were subject to their same standards.
So someone in Montreal (Head Office) had (*ahem*) 'translated' the Gauge R&R as having a time function.
But...No. Nonono.
The tests
only answers the question of whether the gauge is the correct gauge for the job.
If it is the correct gauge for the job today, guess what? It will be the correct gauge for the job tomorrow. Asking to repeat Gauge R&Rs over time is nonsense.
If you do a Gauge R&R
correctly, it is good until you change gauges, or make a radical change to the geometry of the characteristic measured.
Now, that doesn't mean that customers may fuss that they want them done routinely. But, that is just an indication that either they do not trust your ability to do it correctly, or that they do not understand that there is no time function to Gauge R&R.
Trying to convince these people that the MAS, 'Measurement System Analysis' was more important & a much less expensive procedure than the unnecessarily redundant Gauge R&R's was like banging my head against a wall.
