Grinding and polishing glass pieces

August 6, 2008 12:54 PM

Grinding and polishing glass pieces

A follow on to this question:
http://ask.metafilter.com/93916/Optically-perfect-glass

As stated, the borosilicate glass is good, but they are not cut cleanly.
So grinding and polishing the edges would be required.
The pieces could be sized anywhere from 1"x1" to 6"x6", with thickness ranging from 1/16" to 1/4"

What are the machine(s) to do this?
These would have to be affordable machines for a home workshop, like you might buy at home depot.

posted by allelopath to sports, hobbies, & recreation (9 comments total)

I use a wet belt sander with a set of belts from coarse to cork. It's wet, messy and slow work, but they are widely available.
posted by princelyfox at 1:22 PM on August 6, 2008

Have you considered buying glass made for picture frames?

I haven't looked extensively enough to know for sure, but I imagine you could even find some made for covering pieces without frames, and which would therefore have finished edges.
posted by jamjam at 2:18 PM on August 6, 2008

jamjam: we want all the glare, reflections, etc we can get, so that sort of glass wouldn't work
posted by allelopath at 2:26 PM on August 6, 2008

So I understood, allelopath.

Only the fancier, more expensive glass in the second table in my link is non-glare glass. The first section is simply exceptionally flat and clear plate glass.

Mirrors also use glass which is very flat on both surfaces, but I doubt you'd be able to find unsilvered blanks very easily. I suspect a cheap hand mirror with no frame and a muriatic acid bath would give you your desired outcome, however.
posted by jamjam at 3:59 PM on August 6, 2008

You might call & ask about glass blanks at a place like this. They make telescope mirrors & blanks. They seem to know a lot about glass & what different types are available for different purposes. What you're asking for is a bit unusual so it might be better to call & talk with them rather than just browsing around on their web site.
posted by flug at 4:31 PM on August 6, 2008

I have one of these that I used when I was making stained glass stuff. Works well.
posted by daisyace at 7:03 PM on August 6, 2008

This could be a whole lot of blah blah that isn't what you're looking for but anyway.
If they were round (or if this would still be feasible) I would neaten them off by using scoring. Google 'cut glass bottle in half'. There are HEAPS of methods, try all of them. By the time you find one you're happy with you'll have a feel for it and be proficient.

Then... you might get away with one of those little butane torches? You just heat it to glowing and then get it to melt and smooth out. Warm room rather than cold and having two torches with crossed flames (as in the 3 points of a right angle kinda thing) works best.

Some of your glass is quite possibly too thick though??
You need a mixture of oxygen and LPG/Propane, safety procedures.. I think the oxygen goes both on and off first or something? - Get it wrong and it's likely to catch fire or explode anyway.
It's fine if you do it the right way though (ie. Open sliding glass door then walk through. Too easy, huh?)

If this is what you're after I can help with more info for the first two. If you need the hotter flame figure it out for yourself so you understand it all properly but you are absolutely welcome to double check or whatever. If you're not 110% sure - please do!
posted by mu~ha~ha~ha~har at 7:44 PM on August 6, 2008

vibratory lap, patience.
posted by hortense at 8:30 PM on August 6, 2008

A bench top belt sander (ideal) or a hand belt sander you can secure upside down (will work in a pinch) is perfect for this job. You need a 120 or so grit belt that is 80% wore out and a small spray bottle with a mist setting. A fresh belt will work too but it is much more aggressive maybe step up to 150/180. They also sell sanding belts for band saws if you have access to one.

Turn the belt sander on and give the belt a mist with the sprayer. You want the belt damp not wet. Sand on the part of the belt that is unsupported between the roller and the platen. Always keep the glass tipped forward relative to the belt direction (image) and be careful not to dig in the corners. Light pressure is all that is required. Keep misting the belt to keep it damp, you can see when it starts to dry out.

For a very smooth surface finish up with a very fine sanding sponge.

Start with the larger pieces and work your way down. 1x1 is pretty small to hold on to.

This is what glass shops do (with specialized equipment) to finish the edges of cut glass. If you went to one and enquired they'd probably spend a minute and show you what they do. Their machines are generally vertical but it is the same concept.

PS you might want to do this outside on a hard surface that can be easily vacuumed as teeny shards of glass are sometimes generated. The misting will help keep them from floating around everywhere.
posted by Mitheral at 9:22 PM on August 6, 2008