I was at the loading bench yesterday, measuring some cases.. when i was finished, I zipped it closed I think a little too fast, and now it is .017 off of zero. I think it skipped a few teeth..

I tried everything, took this sucker apart (you gotta be almost a watchmaker) and tried to get it reset back to zero. No luck. finally, I unlocked the dial and rotated it to zero.

This caliper is over 20 years old, but has seen very light service and i checked Mitutoyo's website, and there is only info there on how to reset the newer digital ones, but nothing about the older dial calipers.

Fortunately I have a spare as i no longer trust this one.. anyone have any other suggestions?

Frank,is it a dial? What I do with the starretts is take the pointer off carefully it pries off pretty easy. Make sure the teeth are clean set the jaws to zero and put the dial back on pointer to zero.

Part of your problem is your caliper is a dial caliper not a vernier caliper. Vernier calipers do not have a dial, rack or pinion. Your caliper has skipped one or more teeth. You insert a tool in a recess in the top of the caliper behind the dial to reset the thing. There is information on the web. Try searching on dial caliper not vernier caliper.

IIRC a tooth skip in a Mitutoyo dial is .050.
Check the tooth spacing, it is the same as a skipped tooth.
As the result of a drop, mine skip once in a while. Easy to spot when the expected reading is off by 1 tooth (.050).

You already figured out the reset procedure, rotate the dial.

I had a similar problem caused by a small piece of walnut media. You might have some debris in the teeth causing the problem. A can of compressed air might dislodge the problem.

I can't see moving the jaw fast would make it skip a tooth.

And because of chronologically gifted eyesight I went digital with "BIG" numbers. It has a on-off button and a "zero" button for those slippery moves.

The tool has skipped some teeth on the rack and is otherwise fine.

To fix this you need to use a tooth skip shim.

Most quality name brand calipers come with one of these within the plastic case.

If yours didn't come with one or you don't have one, they are easy to make from the bottom of a beer can.

Look to YouTube on how to return to zero by skipping teeth

So that's the little piece of brass in my Mitutoyo dial caliper's plastic case. That instrument has not skipped a beat since I got it in 1983. I have replaced the battery in my digimatic four times since 1988. They are both good pieces of kit. Same same for my micrometers. My most useful tool is the neck thickness micrometer I bought decades ago from Sinclair. I glued on a piece of leather so I can measure about halfway up the neck for most calibers.

Take a cloth and wipe the face of the jaws. Sometimes a little bit of grit will change the "0" reading.