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dropped dial caliper

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  • dropped dial caliper

    I have had my 4-inch Mitutoyo dial calipers for 7 or 8 years now, and today for the first time I dropped them, About 18 inches to the floor. Now they read 0.005 inches when closed. I guess I could turn the dial so they read zero but that's like a "clumsy bastard" tee-shirt. Anyone know how to reset these? Mitutoyo model 505-674. Thanks.

  • #2
    Usually they are supplied with a kind of shim key that is inserted on the rack gear to lift the pinion and jump some teeth on the pointer gear
    Helder Ferreira
    Setubal, Portugal

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    • #3
      It might have skipped a tooth. But before I mess with that sort of thing I'd check that I get the same reading on something when it's at the end of the jaws and at the base. It's possible you bent something so the jaws are not parallel and one of them is not square to the beam as a result. If so then that's what really need to be attended.

      I dropped one of the cheap imports and took on trying to fix it. Be careful with this idea of jumping the gearS over the rack teeth. Yep, the dial works on even the cheapies have TWO pinions that ride in the rack teeth and there's a backlash removal spring between the two. If you lift the gears out of engagement with the pinions and your Mitutoyo shares the dual pinion anti backlash design then as they break contact with the rack the anti backlash will unwind. And then they'll be WELL BROKEN until the dial works can be opened up and the 4 or 6 turns are wound back into the secondary pinion.

      Again I have not had a Mitutoyo apart so this may not be how it's done for that particular design.
      Chilliwack BC, Canada

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      • #4
        Last ones I dropped had to go in the bin, hopefully you make out better than that.

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        • #5
          My 6" Mitutoyo came with a small pin with a flattened tip, as Helder said. When you slide it into the slot at the top edge of the slide it disengages the pinion from the rack. You then slide the movable jaw until the needle points to 0 and pull the pin out.

          -js
          There are no stupid questions. But there are lots of stupid answers. This is the internet.

          Location: SF Bay Area

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          • #6
            I don't think you skipped a tooth . The tooth pitch is around .025" so a .005" shift must be something else. Perhaps the needle shifted on its spindle, or maybe the rack shifted. You could remove the bezel and crystal, then pull off and reset the needle. I've done that, and also reset the anti-backlash spring after dropping. If it is otherwise still satisfactory, perhaps the best approach is to live with it it for another 7 or 8 years. Then maybe you'll drop the other end to the floor.

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            • #7
              If it skipped a tooth, it would be off .025, as stated above. Check for a burr on the tip of the jaws or some other minor ding. Those can be stoned out. Check the reading with the middle of the jaws on a known size of something like a gage pin, gage block, drill bit shank that was measured with a mike, etc. That will tell you if the jaws are off, or only a spot of displaced metal. If the jaws are closed all the way, (check with a .001 shim), just turn the dial to zero and drive on. You will have more problems if you try to reset the needle.
              Last edited by Toolguy; 04-17-2022, 09:30 PM.
              Kansas City area

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              • #8
                I wouldn't be too nervous about shimming to changing the gear alignment. My 4" Mitytoyo have been reset many times over the past 25 years. A shim can be but from pop can aluminum. just slip in and move the jaw a bit, pull the shim,,repeat if necessary until the timing is correct. Good luck.
                BudB

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                • #9
                  Check the jaws, the drop may have bent the tips of the jaws where they're not closing properly.

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                  • #10
                    I may be all wet with my comment, as I don't have any info on the 505-674 ( Nothing on the web )
                    I have a new 505 model as my old one crashed after 40 years and it came with the shim .

                    First, a .100" Dial caliper and a .200 " (0-100-0 ) have different pinion gear arrangements and I used a piece of feeler stock (.003) x 1/8" x 2" to reset the dial on a .100"
                    I think the .200 is easier or more forgiving ??

                    BUT the .100 dial is more difficult because of the pinion spring setting, so this is a easier method --I Think--when you want to reset the dial
                    If you remove the screws on the back of the rack, you can slid the rack out . have the head all the way to the left (closed)
                    Now slid the rack back in , and it will reset the dial point. You may have to try a few times to get a 12 O' Clock position .
                    IMPORTANT. If you can not engage the pinion ( Because it is spring loaded and moves upward, insert the shim first and then slid the rack in and the shim acts like a taper launch site for the pinion.. The rack has a few teeth that engage before it reaches what would be a home position. One of our machinists at work actually ground a short ramp on the left end of the rack on his Dial Caliper , but I am not sure if that would work on your Mit ?

                    Rich
                    Last edited by Rich Carlstedt; 04-17-2022, 11:08 PM.
                    Green Bay, WI

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                    • #11
                      Good call, turns out there is a little burr on the tip of one jaw. It must have hit the concrete floor right on that tip.
                      Last edited by gmax137; 04-18-2022, 01:48 AM.

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                      • #12
                        Always go for the simpler things first!
                        Paul A.
                        SE Texas

                        And if you look REAL close at an analog signal,
                        You will find that it has discrete steps.

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                        • #13
                          Sometimes you can send them back to a Mitutoyo service center for repair, depending on the cost to fix it might be worth it as opposed to buying new.
                          Ontario, Canada

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                          • #14
                            Here's a macro shot, with the TV screen providing backlight.
                            You may only view thumbnails in this gallery. This gallery has 1 photos.

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                            • #15
                              Looks like the thin part of the tips will have to be stoned or shortened by about 1/16". I favour shortening, as it is easy to mess up the undamaged parts. then no light will pass through the jaws. My old Mit digitals have 0.0001" wear in the thin tip sections but they are 32 years old.

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