Mitutoyo 12” 505-645-50 12

I have a vintage Mitutoyo 12” dial caliper that came in a wooden box. My father passed down his 6” Mitutoyo dial caliper that he used regularly as a mechanical engineer. The issue with the 12” caliper is that the small shim tool that is used to adjust the location of the dial only allows the dial to be set either at 0 or 25 or 50 or 75. 0 is 2 thou to the left of 12 o’clock. On the 6 inch Mitutoyo, adjusting the 0 to be at 12 o’clock was easy. This 12” will allow you to place the needle anywhere you want with the same resetting process when the caliper is closed, but as soon as you use the roller to open the jaws, it jumps to the closest 25 thou increment. Any thoughts on getting this to adjust to 0 at 12 o’clock. Thanks in advance.

Pull and reset the needle.

Ed.

That’s beyond my pay grade. I’ll just turn the bezel to match up eight the needle and try to be ok with this caliper not being like my others.

sounds like you may have a piece of something in the rack if it continues to jump. Open it all the way up and check for any bits.

On my Starrett the rack can be loosened and tweaked either right or left to get the needle standing at 12 o'clock. I use a dedicated tooth brush
to clean it often as well as the jaws. What looks clean at eye sight is not the same at 5-10 x. If cleaning the rack gives no change then it is
not hard to disassemble the carriage. There are four screws then you can get to the gear that spins on the rack. It also not hard to lift the
needle off and pop the dial face to get inside.

(One day I left the Starrett on the roof of a car with a rubber top. Then drove to a store and came back, looked for the Starrett and remembered what I had done.
Retraced my path to the store and found the tool in the middle of the road. Nobody ran over it so it was not too bad. Ordered parts for it and brought it back.)

On my Mitutoyo the rack screws are on the back side and the carriage screws are on top. I have no experience with taking apart Mitutoyo but I see
no problem with using the same method as with the Starrett.