SPI Caliper Issue

[ctwo]

As far as calipers go, it seemed like a nice tool. I do not expect great accuracy from any caliper, but at least they seem fairly repeatable.

This sparsely used dial caliper had the tension bar fall out once when I was using it. This is that leaf spring brass bar that rides along the top of the beam. I put it back in and adjusted the screws, but now when I close it, it may read -0.004 or 0, or somewhere in between. It seems to vary as much on a measurement too. It used to be good, repeatable at least...

I wonder what could have happened? Maybe that little spur gear that rides on the rack gear has a bend shaft now or something else?

Anyway, does anyone know how to take that area apart? I can slide off the movable jaw, and usually there are screws on the back to access the gearing, but this one might be pressed together since I can see no screws. It would be worth a look before I give it a good ball peen adjustment. geeze, I'd not even taken off the clear film from the crystal.

[Conrad_R_Hoffman]

If it's like most others, there's coil spring (hair spring) around the pointer shaft to preload it. When the bar fell out, most likely it created enough clearance so the pointer could spin around, losing the spring tension. I'm not sure of an easy fix, but maybe somebody else will know how to do it.

[ctwo]

IF that's it, I can probably fix it. I was getting irritated. Thanks!

Now after my elation wore off a bit and I re-thought what I was thinking, that is I was gonna stick something in and wind up the gear before sliding the jaw back on over the rack, I realize that won't do anything.

I'm pretty sure it's lost it's preload, somehow. I'm not sure how that works though since there is so much travel. I can't see it like a dial indicator that winds up a spring for return...

[ctwo]

Alright, Fixed! There are two spur gears and they need to be rotate slightly apart (or together) to provide some loading. This one will not run off the end at the gear teeth hit, probably a bur on the end of the rack. I removed the lens, then popped off the needle and loosened the dial assembly so I could move it around and hook the gears one tooth apart.

Oh yeah, one reason I really liked these is they have carbide jaws. I don't even see these anymore at Enco or MSC.