Laser Mirror Spanner Wrench / Key

The mirrors on my 50W are held in place by screw-in retaining rings with holes for a spanner wrench to loosen and tighten the rings. Since the mirrors have to be taken out periodically to clean, I needed an easy way to manipulate the retaining rings. Had been using some snap ring pliers, but they aren’t terribly convenient for the tight areas around the 1st and 2nd mirrors.

So, I decided I needed to make a low profile spanner wrench / key. Since this is a low torque situation I opted to just laser cut one from 1/4" plywood.

As best as I could tell, the distance between the holes was 20.0mm and the holes themselves were 2.5mm in diameter. Using some 3/32" (2.38mm) K&S brass rod to make the pins.

Did a quick key design. SVG file below (note it has a white fill so it shows up for people using dark mode) The small bump outs on the pin end are to help with positioning to drill the holes for the pins. Will sand flush after drilling the pin holes.

Mirror Spanner Wrench

Cut from 1/4" birch ply.

Colored the pin end bump outs with silver sharpie marker so I could see the set holes I made.

Drilled 3/32" holes using my Dremel rotary tool drill press.

Removed the bump outs by sanding with my rotary tool and some finger sanders.

The width of the piece that sticks into the center hole is smaller then the center hole except for the corners. So rounded them off with my rotary tool and a small file. Got the fit tight enough so that the ring will stay on the key when fully engaged.

Painted the key red for visibility and glued in the pins with some thin CA glue. Make sure the pins are fit aligned with the retaining ring holes before gluing. I determined I needed about a 5mm total pin length based on how deep the ring holes and drilled holes were.

Works like a charm.

Glued a thin magnet to one side to attach to the outside of the laser so it’s easy to keep track of.


Necessity is always the KEY to making!
Nice work.


Nice job :clap:

1 Like

Pretty handy tool, also the magnet :+1: