[LewisM]

Recently got an SBIG ST-2000XM with a CFW-9 filterwheel. I went to take the filterwheel face plate off last night to clean the filters and install an H-a in the place of a second Lum the prior owner installed, but 3 of the tiny hex-head screws holding the cover plate on are seized.

I gingerly tried using the long side of the allen key for leverage, but I fear it was going to strip the hex hole before undoing. All the others "snapped" open (distinct click when freeing them), but show no signs of Loctite, so I assume just alu-alu seizure/corrosion.

Seeing this is a filter wheel, with rubber traction wheels, delicate Astonomik filters and other electronic wizardry, I dare not try direct application of heat or even a heated rod directly to the head. I fear the only option will be a small left-hand twist drill. (I have never seen an Ezy-out with a small enough shank either). Once I start, there is no turning back.

Suggestions from the Peanut Gallery?

Also, what size are these screws - I assume imperial sizing - so I can source replacements.