Plastic Screw-top Flashlight Fix

As part of my clear-off-the-workbench effort, this flashlight emerged from the dark depths. It’s a few decades old and wasn’t a good design: the “switch” is a simple contact between the end of the cell casing and the reflector rim, activated by screwing the reflector tighter on the case.

The failure is simple: the case cracks through at the stress raiser formed where the “switch” contacts rest on a sharp inside corner. That stiff little spring maintains pressure on the cells, so the case is always under tension and eventually fractures.

I grabbed the broken pieces in the lathe, turned off the fractured plastic, and wound up with a pair of nicely mating surfaces (and a somewhat shorter flashlight, but it’s still long enough). Apply enough Plastruct solvent glue to soften the new faces, then clamp them together. The big manual mill knows how to apply a strong, steady vertical force to a project like this.

It’s once again hanging by the basement door, where it gets used roughly once every other blue moon (yeah, it’s color-coordinated). This isn’t the first time this flashlight has failed that way, but it’ll be the last: next time, it’s in the trash.

Honest, I swear it!