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Having a go at making a mirror


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I don't know why 3mm bevels are essential. More hours of work to go? I'd maintain what you have now that you're down to 400 grit.

!00 grit diamond Swiss files are cheap followed by a smoothing 400 grit file or your stone. Will the bevel reduce that much during the finer powders?

Does the little chip matter that much?

David

Edited by davidc135
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Since my observatory project is on hold pending funds and some warmer weather, and the setup I have is working okay, I figured I'd try my hand at making a telescope. My plan is to do this in stages -

A few thoughts. Having made a number of mirrors I  can confirm that keeping things wet will totally eliminate any dust to the extent that you do not need any eye or face protection. Nothing flies

Well, I'm getting somewhere! Definitely making progress with removing material now. My grinding down of the sharpie marks at the edge suggests I'm pretty symmetrical overall but doing basic

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Sorry guys to chime into this thread, but bevelling a mirror should take no more then about 15 minutes or so.
A few days ago I did a 12", it took me about 20 minutes. Be not afraid to push on that stone.
But : always work with plenty of water and ALWAYS  grind from the inner to the outer side of the mirror. Starting a new stroke, do not hit the mirror hard with that stone.

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Right, well, it turns out my whetstones were just rubbish. Thanks all for the comments - knowing this wasn't right was what pushed me to fix the problem!

20 minutes with the new diamond pads and I have a 3mm bevel now. I used 60 grit initially and then 200 grit. I might get a finer grit to finish with but it's already OK really, and chip-free - a pass with the 200 took all the remaining little chips out. I'll see if I can get a 400 pad tomorrow and if not may just crack on with the grinding.

Edit: for documentary purposes, here's the (still wet) bevel. It's slightly rounded which is fine - the diamond pads are on a very stiff foam which allows for a tiny bit of deflection, allowing a nice soft bevel to form quite naturally by moving the tool around the edge. For the 60 grit I used a downward stroke to avoid causing chips - on the outer edge there were quite a few chips formed, so this was definitely worthwhile.

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Edited by discardedastro
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Had some more time to work on things (I've had quite a bit of time, but Critical Role ( https://critrole.com ) has taken up much of that) and had gotten the surface ground nicely with 180 grit but had to go at it a bit more tool-on-top to get the ROC back to where it should be. All sorted now.

I've had a first go at cleaning up the tool but I think I need to go at it with a brass wire bush to get the grit out as just melting the beeswax wasn't convincingly removing the grit. In any case, some progress. Need to get the cleaning setup reasonably slick if I'm going to be doing this often (as I hopefully will be as I progress through the grits).

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