I noticed a little flexing and figured that was introducing some error. I thought of mounting them by drilling a hole in the end of the bar, and attaching to a post that had a some kind of ecentric that would pull tension on the bar.
Might be over kill, but may cut the error.
Hardened stainless is tough to drill, but I managed it on a set of calipers once with a carbide bit.
Hope you didn't get the wrong impression... I'm not knocking these units at all. They are fine for a lot of people for a lot of things. Their stated accuracy is (depending on what literature you read) +/- 0.001". I think that's how accurate the tracking head can operate but speaks nothing about the method of mounting and flex. Since I have a set of these and have looked things over carefully, they seem to work within +/- 2 or 3 thou for most things. -And for most things, that's good enough.
Higher end DROs have stated accuracy of 0.0002 or 0.0001" inch. That's a joke really. For all practical purposes, no lathe or mill that anyone here can afford is going to produce finished quality in those tolerance ranges. In cases where things are really critical a homeshop machinist will only need to get within +/- 0.0005". For all my general purpose work, I aspire to keep things within +/- 0.00075 (or better). If you practice long enough, you'll find it's not hard to do. On rare occasion I really need something to be -0.0000, +0.0003 and in such cases, I rely on DRO to get me close but use the mics to finish off...
For every digit in the 4th decimal place to the right (i.e. 0.0005 vs 0.0004 vs 0.0003...), it takes about 10-20 minutes more setup time and double checking before you make the cut. In the 0.0004 and below range, you need your thermometer and expansion tables handy.
Moral of the story, for folks with vintage machines or hobby-class stuff who are drilling holes in aluminum, those Igaging DROs are fine 90% of your work. If you're making precision parts or doing gunsmith work, use good DROs, Mics and Calipers etc...
Ray
