Disappointed in MiterSet

[dusty]

Dusty,

Only thing I can think of is there "might" be an issue with inside versus outside measurements with your calipers. On the surface, that is the only thing different between all of your measurements, i.e. one side of caliper is measuring inside the miter slot and other side of caliper is measuring outside of miter bar. Is it possible there is some fixed offset in your calipers for inside measurements that is causing it to be lower than actual?

It looks pretty straight in your pictures, but also if you were at an angle measuring inside dimension then the measurement would be smaller than actual. Conversely, the outside measurement, if taken at an angle, would be larger than actual. I don't really see this in the your pictures that I can tell, i.e. the calipers look straight and aligned with what is being measured.

What will demonstrate if I measure a set up block (known dimension) with a pair of calipers (inside jaws) and then with a different set of calipers measure those outside jaws. In a perfect world - all measurements would be identical - right?

Go one step further and use each caliper to measure the other caliper - inside to outside and outside to inside. Again, all measurements should be the same.

Turn the calipers off (they self zero with the jaws open when turned back on). Now close the jaws of both calipers. Perfect measurements will result in identical readings equal to the original setup block. Any reading other than identical indicates deviation somewhere.

I would hope for no deviations at the third decimal.

That’s what I do, Dusty. Except that I use a micrometer instead of the second set of calipers, because that’s what I have.

My second-hand Mitutoyo dial calipers are off 0.003” between the inside and outside measurements. Someday, I’ll have them repaired/recalibrated. For now, I just compensate by adding 0.003” to the inside measurements.

The dilemma becomes which one is right or wrong and/or how to distribute the error correctly.

[BuckeyeDennis]

The dilemma becomes which one is right or wrong and/or how to distribute the error correctly.

I always zero my calipers with the jaws closed, which ensures that the outside-measurement zero offset is correct. I've also verified the "gain" using precision 1-2-3 blocks. Thus I only have to compensate the inside-measurement offset.

One caveat -- I did confirm that both my inside and my outside jaws are nice and parallel. If they aren't, that's a whole different can of worms.