We frequently calibrate gages and instruments in the dimensional field for labs that primarily deal with electronic or other disciplines. This occurs when their customers try to cut corners by adding one or more dimensional items onto an order they have received for their normal work.

Trying to keep a customer happy, they’ll subcontract the work to folks like us and all will be sweetness and light—until it isn’t. And when it isn’t, it usually works out that the ‘favor’ being provided costs everyone more than it should. Full disclosure: I know just enough about electronics calibration to realize I don’t want to go there so I don’t.

Yes, the original customer saves the cost of issuing a separate order for a couple of items but often loses money because they’ll have to pay the electronics lab their costs of handling the order. Things get messy when the assumptions followed for electronics calibration aren’t the same as those followed in the dimensional field. The resulting discussions—or often arguments—cost both labs time and money.

A recent case in point involved some setting rods for micrometers ranging in size from 29” to 39” which were duly calibrated by us and a report issued. This resulted in an irate call from the electronics lab claiming we didn’t know what we were doing. Discussion with the office person who set up the order and the calibration technician did not satisfy the situation and the caller insisted on speaking to a manager so it ended up in my lap.

A copy of the report was handed to me as I picked up the call and after things cooled down a bit, tried to figure out if or how we appeared to have screwed up. It turned out that the electronics folks expected that since these rods were adjustable, we should have done so and brought them to a ‘zero’ condition before returning them. This was the first time I had encountered setting rods of this type that had such a feature but then, I’ve only got about sixty years’ experience in the business so I’m still learning.

My caller suggested that I check with my technician and call him back in a hour which I agreed to do. And did. And it got worse from there. 

Electronic tests instruments usually have a built-in adjustment to bring them into a certain range and this is done during calibration which explains why the electronics lab assumed that would be the case with anything adjustable in the mechanical field and so they never requested it.

We offered to do such tweaking as an extra but the cost of the job would go off the chart because we would be chasing millionths of an inch fiddling with a very crude adjusting device. A cooling down period would be required after each adjustment and many would be required before any material improvement was obtained. It would be a hit and miss affair—something I wasn’t excited about getting involved with. What could happen when we tried to lock a setting in place could become another nightmare.

And then I learned that these rods were spherically ended which meant that repeatable readings would be even more elusive.

Considering their size, the readings we reported on the rods appeared to me to be quite good given the limitations of our field but I knew that would not wash with ‘if it ain’t zero, it ain’t good’ folks so I decided to look further. 

When our readings were compared to the specifications of new fixed rods from one of our industry’s leading makers, every one we had calibrated met those specifications. I decided to quit while we were ahead.

I explained all of this to our customer who relented when he realized the limitations of dimensional measurement. I asked what industry these items were being used in expecting to hear it was some project for NASA or possibly some experimental nuclear lab only to learn it was for a machine shop that did big work… Who would have thought?

When I indicated that as soon as someone put such a large micrometer in their hot little hands, the accuracy of the rods would go out the window, my customer’s newfound awareness came to the fore when he said they should be using something better than micrometers for the job. 

I couldn’t have said it better.