Most machinists know that if you need accuracy to a thousandth (0.001″) or better, you can’t use a calipers. At the same time, the digital calipers is such a convenient tool for ID, OD, and length measurements. Machinist’s of yore were fond of their steel rule, but many of the newer generation are fond of their digital calipers.
Is there no way to make the darned things a little more accurate?
Enter the Caliper Pressure Device.
I’m going to call it a “CPD” rather than spell it out every time, but the basic premise of the CPD is that the accuracy issues of a digital calipers are due to flex associated with uneven application of pressure. We all know that if we anticipate the measurement we’d like too much, we are more likely to get that measurement, even though it isn’t real or repeatable. So the CPD is a spring loaded device that applies the same relatively modest pressure every time:
The CPD can press against the caliper from either direction of travel…
There is a constant pressure spring inside the barrel
Fancier versions are available…
The CPD is available from Danish company Flexible Measuring Systems (FMK). No sign of what they cost, but I am genuinely curious how well they work, being a nut for new measuring devices. The company claims their gadget will boost the accuracy of a digital calipers from 0.02mm to 0.01mm, which ought to be enough to measure to 0.001″ reliably.
Now why doesn’t some caliper manufacturer build a caliper that has a spring loaded jaw built right into the housing so you don’t have to do it as an add-on?