Precision Is Only One Option With This Tool
May 15, 2014
I'm far from a machinist, but I own three calipers, and wouldn't mind owning one or two more. Calipers are those measuring devices that are shaped roughly like a small, flat pipe wrench. They're used for obtaining precise measurements. High-end, $125 digital calipers accurately measure to ten-thousandtsh of an inch.
My $5 plastic caliper is probably accurate for measuring down to eights of an inch. My $15 metal caliper is good down to sixy-fourths of an inch. My $40 digital caliper is good for thousandths of an inch, when I can keep a decent battery in it.
I'm content with the accuracy my cheapo set of calipers provides me. Most of the time I use my the plastic or metal caliper to compare sizes of objects. If I need to know if a shaft and bearing are going to be compatible, I size one of those calipers to fit the shaft, then hold that setting and see if it does or doesn't fit in the bearing. For generic measuring of shafts, sprocket bores and other round or holed objects, being able to measure within 1/32 of an inch on the crude scales of those economy-grade calipers is close enough to allow me to make the comparisons I need.
If I need to know more precise measurements, like if I need to know a shaft's diameter within 0.01 inch in order to match it with a specification in a tech manual, I get along well with my low-buck digital caliper. For some reason it won't last more than a month or two on the watch battery that powers it, even if I keep it turned off in its storage case. I've learned to keep a couple spare batteries in the case, and despite that annoyance, that caliper serves my needs well for the infrequent precision measurements I take.
Calipers aren't a high-use tool for me--maybe once or twice a month. But I've come to depend on them when I need them. If I break or lose one, I replace it as soon as possible. They aren't essential tools, but handy tools to have, even for somebody as imprecise as me.