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Old 17-04-2017, 08:26 AM
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sopticals (Stephen)
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Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 226
Hi Neil, I don't see anyone else jumping in here. Been a long time since I've used full sized tools on small mirrors.

Looking at the wear on your tile tool, it appears that overall contact between mirror and tool isn't that good. Probably because you started out with such a fine grit (#220). Normally one would "break in" such a tool with #80 (or coarser for bigger mirror) to quickly grind off "the high ground" and "raise the valleys".

IME with larger mirrors and small diameter hogging tool and sub diameter tile tools (which have 100% contact), I find the center depth target does arrive more quickly, and outer regions lag behind somewhat, (particularly the 70% zone). To deal with this when target sagitta for center is close/there I concentrate strokes on the 70% zone (which also helps the edge "to catch up"as well).

Stephen.
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