After the failure of my first "porcelain" tile tool, I ended up getting glass tile mats
with 1x1 squares.epoxied these to my original 15" F-5 pitch lap base and went at it.
Took a bit of manual labour with 80 grit to get them set close enough to the curve of
the glass so the tool would spin properly on the glass but once it did things went well.
worked with 80 grit and maybe 3/4" overhang and 30 pounds of weight on top of the
tool to deepen curve then I switched to 120 grit to smooth things out, ground
there till I was sure tool and glass where close to mated as possible then I moved the
tool out to 1-1/2" overhang and ground with 120 for 1 hour, once everything was working
good and pit size was the same I switched to 220,with 15 lbs weight on tool ground for
about 1/2 hour then moved the tool out to a 2" overhang and ground for 45 minutes more,
RoC was 183.
Switched to 320 with 10 lbs on tool and ground for 1 hour, did marky test after 45 minutes
and confirmed the surfaces of both the glass and the tool were mated,
Next was the 25 M with no added weight and did 1 hours with this, tested for pit, tested RoC
to be 182.5.
did 9u next for 50 minutes then had a big bo bo "scratches" tried for 20 minutes to grind them
out with the 9u but even though it help, decided it was probably 2 hours work to fix this bo bo
so I instead went back to 12M ,after 40 minutes with the 12M the scratches were gone so off
to 5M this time
5m went real good, 40 minutes worth, no pits and sharpie test confirmed real good mating of
tool and glass. I was so impressed that I decide to go the one step further and did some 30
minutes with the
3M, all end up great, never so much as saw a sleek and the pits are all even
in size, best of all the RoC is currently 181"., not bad for a 180 RoC target eh.
Polishing is next, will keep ya posted.
the 20" glass was F-5.125 and I was changing focal length to an F 4.5.
Edited by Stargazer, 21 August 2019 - 09:05 PM.