Hi Stevie

Have you tried a google search? I found a repair solution to a digital micrometer that way and Mitutoyo spares were really helpful with the required part.(sent me an exploded view diagram to help positively identify it)

On the digital version there is a collar with a grub screw with a tiny pin end which has to be removed before you can withdraw the spindle. If you don't do this the pin breaks off (sacrificial detail?) The pin is a very precise fit in a groove which runs along the spindle and on mine transmits rotational drive from the spindle to the digital encoder disc.

I wonder if there is something similar on yours which would account for the erratic movement of the counter. I could imagine a similar collar with a drive dog on it which moves the right hand dial and the collar being connected to the spindle in a similar way to mine. This arrangement allows the spindle to move lengthways while transmitting rotational drive from the spindle to the counter. If so my guess is that you remove the two screws from the top of the counter to expose the collar and grub screw behind. I am trying to remember if here was actually the grub screw and then a very short locking screw on top of that, I seem to recall that here was but could be wrong.

If the worst comes to the worst, you can measure just using the graduations on the Thimble against the fiduciary line on the Barrel.

Ideally, it will read zero, on a good flat surface, with any of the measuring rods..

You look to have got yourself a good quality depth mic for a fraction the price of a new one.

Howard

Micrometer scale!

Well done Stevie

sounds like it was indeed similar to what I was trying to describe- what I called a tiny grub screw with a pin on the end is what is actually called a key screw. And this then has a second retaining grub screw on top?

The collar as I called it appears to have a finely serrated gear on your mic, which is what drives the counter?

was the key screw damaged at all ? The tip of that component is very fragile and the one on my mic had been damaged which is why I replaced it. This might be why you find yours is not reading precisely. The profile of the top may not be sitting accurately in the groove as it might not extend down into the groove quite as far as it should.

if the tip has snapped off it will mean that the shoulder on the screw will rub on the spindle before the tip of the pin / key gets to where it should be within the groove.

These instruments are precision made and that part is really like a watch component. I suspect the pin/ key is designed to be sacrificial so it does not damage the spindle it keys into.

I think the damage occurs when someone tries to dismantle the assembly without first removing the key.
if yours is the slightest bit rough in use it may be worth getting and trying a new key from Mitutoyo.

with a quality instrument like that it is so nice to have it ‘spot on’!

Thanks Steve

That info now stored in my mind – it is useful to know how these things are designed and put together as it helps when coming across a similar problem on a different tool.

I have the Mitutoyo micrometer with similar digital readout so that my well share the same innards as yours.

again well done sorting it

John