My grandfather, who had been a tool & die maker in San Francisco in the 20’s and 30’s, instilled in me the habit to always buy the best tools available, period. One of the first tools I was required to buy when I entered trade school was a caliper. At the time you could get either vernier scale or dial calipers. Well the dial calipers were the new thing, so I went out and bought a pair of Starrett Dial Calipers, the best American made tools at the time, at about a week’s wages. I was so proud and took extra care of them, but to my dismay, within a year I found that they, and almost all dial calipers, had a fatal flaw. The dial is driven by a very small pinion gear that rides on a very small rack, and the rack had a tendency to pick up fine chips and grit in the teeth that were very hard to clean out. This in turn caused to pinion to skip and would cause the dial to jump its calibration. I had my first introduction to this problem when I was working on a camera part and all of a sudden it seemed all my dimensions were off by .025″ (this is a lot in the world of precision). This cost me a day’s work plus I had to fess up to my boss, a real tyrant, about my problem, and was he pissed! Well about five years later a colleague of mine showed me the “new new” thing which was a digital caliper. This caliper works on an electro-magnetic field so there are no moving parts to speak of, just the reader head sliding along the scale. This requires a wipe down with a clean rag every couple of days of use. The other features that made the digital version so much better was you could set the zero any place you wanted. So you could zero on a master part, and then check all succeeding parts and instantly know if they were plus or minus of the master. Also you could switch from inches to metric with push of a button, very handy for working on things made overseas (metric).

Without a doubt my favorite digital calipers are the 6″ Digimatic made by Mitutoyo. Mitutoyo is among the first to make digital calipers and seemed to get a jump on everyone else. Remarkably that seems to still be the case 20 years later. The Mitutoyo are the most copied, knocked-off calipers on the market. A friend of mine recently acquired a set of Swiss-made digital calipers and although they work well they are a little clunky and the sliding action is a bit rough.

I never cease to be amazed at the number of things I use my digital calipers for, out side of working in a machine shop. I keep one of my old sets at home and I use them all the time.

-- Chris Rand 12/28/05