Mitutoyo dial caliper

[grim_d]

I've just acquired a mitutoyo dial caliper, needs a bit of tlc. Model number 82.

It's filthy, the jewel is cracked,the plastic stop at the end of the slide is missing and the thumbwheel is missing.

On the back it has the previous owners name and "on comp of appr at FMP 1983" I assume this is on completion of an apprenticeship in 1983, does anyone know what FMP is?

Also if anyone has a similar caliper could they possibly give me the dimensions of the thumbwheel? I'd like to make one true to original

 

[graffian]

I can do that. Just noticed I didn't dimension the inner edges of the slot, the narrow bit is .425" diameter.
As you can see it's not symetrical, noticably so and the narrow slot is not symetrical in the slot. I don't think
dimensions of any of that matters. The wide bit of slot goes over the caliper, only just; this came off a caliper
from the early 80's, a new digital caliper has the same diameter wheel but it's about 25 thou wider and the
caliper body is wider.
The pitch of the knurl I measured at .033", that will be closeish to what it is.

Mine are 505-634 and 505-627 probably the same age as yours.

 

[grim_d]

@graffian

That's brilliant, thank you very much, I've got a nice bit of stainless ready to go, though I'll need to figure out why it reads 20 thou out first

I was going to copy the one from my digital calipers so glad to know it's slightly different.

 

[graffian]

It reads out because the pinion has jumped a tooth on the rack. Just turn zero the dial. I did restset one once, get a thin bit of wire and run the pinion onto it and it will jump, do it until the needle is pointing where you want. I suspect that isn't advisable, but I did It to a caliper and it didn'seem to do it any harm.
Keep the rack clean, I sort of pick the **** out of the rack with a strand of fine wire.

 

[brightspark]

It reads out because the pinion has jumped a tooth on the rack. Just turn zero the dial. I did restset one once, get a thin bit of wire and run the pinion onto it and it will jump, do it until the needle is pointing where you want. I suspect that isn't advisable, but I did It to a caliper and it didn'seem to do it any harm.
Keep the rack clean, I sort of pick the **** out of the rack with a strand of fine wire.

If i get any crap in mine I open it fully spray it with wd 40 and blast it facing away from the dial with compressor with a welding blow pipe

 

[grim_d]

@graffian

I mean if I start at 0 and measure something that is exactly an inch it will read .980

 

[graffian]

20 thou! Mine underreads by less than a thou all the way to 8", so that's what I would expect.
They over read a few thou if the rack is dirty, the rack still feels ok at that error; Over read of 5 thou from
dirt and the rack feels like it's got boulders jammed in it.
Check it with a range of measurments, see if it's just in one area.

 

[grim_d]

I have to admit it does feel like it has boulders in it, it needs a damn good clean