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Archive for May 31st, 2009

Digital Caliper Roller Repair

Broken caliper thumb roller mount

Broken caliper thumb roller mount

The thumb roller fell off my digital caliper in the heat of a project, forcing me to deploy a hot backup from the upstairs desk.

This looks like a clear-cut case of underdesign, because it broke exactly where you’d expect: at the midpoint of the arch. Having my thumb right over the spot marked X, though, meant that I had all the pieces and could, at least in principle, glue everything back together.

Glued and clamped

Glued and clamped

As with all repairs involving adhesives, the real problem is clamping the parts together while the glue cures. I clamped a stack of random plastic sheets to the back of the case to establish a plane surface behind the mount, with a small steel shim to prevent the top sheet from becoming one with the repair.

The roller shaft was about the same size as a #33 drill and the opening was about 110 mils. Some 3/32″ (actually about 96 mils) rectangular telescoping brass tubing was about the right size & shape to hold the opening in alignment. Another length of tubing kept the broken part from sliding to the left.

A dab of solvent glue (I still use Plastruct, but it’s not like it used to be before it became less toxic) on both pieces, line ’em up, apply a clamp to hold it in place, and let it cure overnight.

I have no confidence that this will stay together for very long, so I’ll probably be forced to mill a little replacement mounting doodad.

Ought to be good for a few hours of quality shop time…

Memo to Self: Don’t run the slide off the end of the body, because that rubber boot is an absolute mumble to put back in place.

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