Glass polishing....It worked !

[steve1811uk]

Hi, just wanted to share in case it helps anyone. I made my first attempt at glass polishing recently and was very impressed with what I achieved as a first attempt.

Equipment used - Flat machined steel block approx 100 x 150mm.

Consumables - Silicon carbide grit paper, grades 600, 1000, 1500, 2000, 2500, 3000, 5000, 7000.

Also diamond based polishing compounds, 2.5, 1 and 0.5 micron.

I started off with the 600 paper on the metal block slightly wetted. I used some used rodico on the inside of the glass to protect from any stray abrasives. I spent less than 2 minutes rubbing in a circular motion while periodically rotating the glass by 90 degrees at a time. A milkyness would appear on the paper and that was the abraded glass particles.

Then I moved on to the next finer grade. Between grades I would wash the glass surface and also wash the new piece of abrasive paper to get rid of any stray abrasives particles.

After each finer grade the translucence of the glass would be improved.

After 7000 grade there was a certain kind of speckled textured when looking into the light through the glass.

At this stage I used the 0.5 micron diamond paste on a small cotton Dremel wheel and ended up with a bit of a fine orange peel effect. Nicely polished but not what I wanted. I reverted back to the 2.5 micron paste and then used the 1 micron followed by the 0.5 micron and this gave the result I was after without any orange peel. Looking back I think that the 1 and 0.5 micron pastes didn't add much to what was achieved with the 2.5, maybe they made the glass just a bit more reflective.

If I was to do it again I would try and find some finer grade papers than 7000 and try and use those instead of the diamond paste to keep everything optically perfectly flat. Also I would try to minimise the glass loss of thickness as much as possible by using the harsher grades as little as possible (I ended up at 1.38mm from 1.45mm that I started off with, just under 5% loss).TBH though I am very happy with the results that look pretty much perfect to me.

[mikepilk]

Nice job. 

It's worth noting that if you can find a replacement in the correct size, glasses are cheap .e.g. 1.5mm mineral glasses from Cousins are about £1.50

[steve1811uk]

57 minutes ago, mikepilk said:

Nice job. 

It's worth noting that if you can find a replacement in the correct size, glasses are cheap .e.g. 1.5mm mineral glasses from Cousins are about £1.50

Of course, but this was a Seiko metal framed bonded glass from the 1970s and was unobtainable.

Just now, steve1811uk said:

Of course, but this was a Seiko metal framed bonded glass from the 1970s and was unobtainable.

With a fully polished bevelled edge. I did look for a glass with polished bevelled edge but couldn't find that also.

This has got me thinking now. How easy would it be to grind and polish a bevel onto a new piece of flat circular glass? I'm thinking Dremel tool, some kind of flat metal disc to stick the glass to with a thin post on the back to go into the Dremel chuck. Could shellac be used to stick the glass in place?

[Paul80]

Even if a replacement is available it's still a nice feeling to say I did that myself.

Well done

[VWatchie]

On 9/12/2023 at 8:06 PM, steve1811uk said:

If I was to do it again I would try and find some finer grade papers than 7000 and try and use those instead of the diamond paste to keep everything optically perfectly flat.

Thanks for your walkthrough! 

Was this a mineral crystal or a sapphire crystal? I'd very much assume it was a mineral crystal as I believe I read somewhere that sapphire is more or less impossible to polish, no?

I tried to find some finer grade silicon carbide grit paper than 7000 but the only one I found was this 11000 grit (2 micron) paper. Perhaps it would be useless with grits in between 7000 and 11000 when reaching such a fine level. Anyway, do you think 11000 would be fine enough? After all, there's quite a difference between 0.5 and 2 microns.

[rossjackson01]

Steve. Thank you. This post now marked in my favourites/Watch Repair/ Learning tips

[Neverenoughwatches]

On 9/12/2023 at 8:13 PM, steve1811uk said:

This has got me thinking now. How easy would it be to grind and polish a bevel onto a new piece of flat circular glass? I'm thinking Dremel tool, some kind of flat metal disc to stick the glass to with a thin post on the back to go into the Dremel chuck. Could shellac be used to stick the glass in place?

Yes it is possible to grind in a bevel edge to a flat glass. I made an attempt a couple of months ago at removing some chips from a bevel. I used a diamomd plate and some fine grade wet and dry . Revolved the glass by attaching it to a sucker in a  bench mounted drill.

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