After my post yesterday about variations in digital calipers I took the advice of an experienced model engineer and used material of known dimensionsl. In my case a set of ground parallel metal bars. One digital caliper, the digital micrometer and the screw driven micrometer all performed well giving the same results. However two other digital calipers varied each time (I open, closed, reset them each time) but as much as 4 thou. may not seem much but it is.

So what am I going to do about it? Well in part my faith has been restored as I have one digital caliper working fine so Its a case of keep checking the good one against either of the micrometers. As to the others, well they will be stored somewhere 'safe'. It has been a worthwhile exercise and perhaps with digital calipers cheap may not necessarily be best!