# Clean and restore Mitutoyo dial caliper



## GreatOldOne (Sep 19, 2019)

My friend recently purchased an old dial calliper from eBay, and asked if I could try and polish out the scratches in the crystal. So I gave it a go, and whilst I was at it stripped it all down and gave it a thorough cleaning, as it was real grotty in places.

Before:





During:






After:



Everything was cleaned in isopropyl alcohol, and the crystal was polished with 120 thru 2500 grit wetndry, finally finishing off with a cotton mop on my Dremel with some polywatch plastic crystal polish. It’s got it nice a clean with all the deep scratches out - but has highlighted that the two worst scratches are in fact cracks. He’s going to run with it for now, and probably get a new one later.


----------



## mikey (Sep 19, 2019)

You did a really nice job on that! Is it accurate?


----------



## fixit (Sep 19, 2019)

you should go into the repair business. GREAT JOB, young man.


----------



## thomas s (Sep 19, 2019)

very nice can I send you a few for repair lol.


----------



## GreatOldOne (Sep 19, 2019)

mikey said:


> You did a really nice job on that! Is it accurate?



Yes, it’s accurate. Checked with my gauge blocks. 



fixit said:


> you should go into the repair business. GREAT JOB, young man.



Thank you!



thomas s said:


> very nice can I send you a few for repair lol.



Shipping may be prohibitive...


----------



## tmenyc (Sep 19, 2019)

do you know what the crystal is made of?  Is it a plastic of some kind?  Almost any plastic can be solvent welded and polished so the crack is gone. 
And yes, phenomenal job!  Encourages me to go after the old yellowed Starrett I have; I think it was yellowed by being in a kerosene-heated shop with a heavy smoker...

Tim


----------



## GreatOldOne (Sep 19, 2019)

tmenyc said:


> do you know what the crystal is made of?  Is it a plastic of some kind?



Yes, it’s plastic. I would guess it’s some form of polycarbonate. Sanding out the scratches produced the same sort of fine particles and plasticky smell as sanding and buffing out lenses on non glass headlights.


----------



## brino (Sep 19, 2019)

GreatOldOne said:


> It’s got it nice a clean with all the deep scratches out - but has highlighted that the two worst scratches are in fact cracks.



Nope can't polish those out.
Very nice job!
-brino


----------



## tjb (Sep 19, 2019)

Beautiful work.  Just last week, my daughter-in-law found a Mitutoyo 505-625 dial caliper and gave it to me.  It's in very good condition but a little grimy.  Your post encourages me to try to give it a good cleaning.  Thanks.

Regards,
Terry


----------



## Janderso (Sep 20, 2019)

Outstanding work!!
I have an old Brown and Sharpe that needs the same attention.


----------



## Bob Korves (Sep 20, 2019)

Cut the new bezel from polycarbonate sheet (I get small sheets free from Tap Plastics.)  Install it like this:




You do not need the Mitutoyo tool, just make yourself a quick and dirty equivalent...


----------



## Sheather (Sep 20, 2019)

If you are only doing a few, the Harbor Freight watch press is a very inexpensive option for installing crystals. 

The only modification needed is to dome one of the nylon dies that come with it. This is easy enough to do on a lathe. As they come, the die edges are too rectangular and can deform your nice new replacement crystal instead of leaving it with a smooth, even curve. I learned that the hard way, so you don't have to.


----------



## Bob Korves (Sep 20, 2019)

Sheather said:


> If you are only doing a few, the Harbor Freight watch press is a very inexpensive option for installing crystals.


That looks like a perfectly good way to install crystals on machinist indicators for low $ and little time invested.  The HF part number is 91621.  I will get one myself, probably way better than my cobbled up contraption (which does work...)


----------



## Round in circles (Sep 20, 2019)

Made a lens for a pressure gauge out of 1.5 mm polycarb   cut  3 x 3 square to be screwed to a bit of planed inch thick wood through the centre of which I put a counter sunk coach bolt ,  added half a dozen nuts  and put it on the lathes face plate then trued it up before attaching the predrilled poly carb square with mushroom head wood screws.. across the whole of the square I used  double side sticky tape to hold the lens in place when it separated then turned the disc from along the bed with a fine ground tool tip  to just over size of the bezel  including the lip . Made my own cups & a plunger  on the lathe and then inserted the lens using the drill press table , cup & plunger to cup it .


----------

