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Wooden Polishing Tool

Started by tbennett, 09/01/2022 11:18PM
Posted 09/01/2022 11:18PM Opening Post
Has anyone used a wooden disk as a pitch lap base for polishing mirrors?

I've got two 10-inch F/4 mirrors and a 10-inch F/6.5 mirror that need refiguring and glued 3 baltic birch disks together for use as a pitch lap base shown in the attached images. After applying a belt-sander to make it a little convex and marine varnish to water proof it, I plan to pore a lap on this wooden base.

Is there some reason this won't work? Thanks!

Attached Image:

tbennett's attachment for post 192984
Posted 09/04/2022 12:43AM #1
I don't know if wood works as a base for a pitch lap but back in the day when I made a couple of mirrors, the kits I used came with ceramic tools. Anyhow, if you use the standard pitch and polish materials, and the wood isn't affected by the heat of pressing the mirror to the lap for polishing/figuring, then I'd think you'd probably be ok. Good luck with it and let us know how it performs...
Posted 09/04/2022 08:59PM #2
I also remember buying a 6-inch ceramic tool mirror making kit from Telescopics in Los Angeles back in the 1970s as a kid. The Foucault shadows for that F/8 mirror were real subtle and didn't take much parabolizing.

One of the F/4 mirrors (from a TS Optic OTA) I plan on refiguring shows a smooth conic-section but over-corrected by about 2/3 waves. The other (from Chinese source) is showing so many zones - it's hard to get an SA reading. For these faster mirrors, I recall having to figure them slightly under-corrected to make up for the Foucault light-source and knife-edge being slightly separated. I have some left-over rouge but will have to order some fresh pitch to get started.