Where do get custom size optical blanks cut?

[skybadger]

It's time to make some mirrors. This is going to be a Cass secondary. Have both some thicker blanks 8" square by 1.5" thick  and some thinner 6" round by 1". I can either buy a custom pair or I can get them cut from my existing stock. Anyone know a water cutter in Berkshire or can I take it to any old glazier ? I need a pair 92mm round by 12mm or so.

Cheers 

Mike

 

[Merlin66]

What about trepanning them yourself using a thick plywood base, tin sheet cutter and a drill press? Needs a stock of #80, or#120 grit and some time.....

We used to make our own 8" blanks from used porthole glass in the 70's

 

[Chriske]

yep, trepanning is a solution. I have a set of these, works just perfect and very fast to.

[Merlin66]

An interesting option!

what's the maximum glass thickness can they cut????

 

[Chriske]

Don't know but I already cored a 16mm thick glass blank with it. It' s a matter of a just a few minutes.
If you do use these coring bits, you need to do this with water, LOTS of it..! I did it using a speed of about 250rpm. Mild pressure. It's rather noisy.

[Merlin66]

Cutting the larger blanks >20mm would be a challenge.

the traditional trepanning set-up would be more versatile.

 

[skybadger]

Thanks all, I can trepan the blanks I have but it's quite wasteful for cutting disks only just larger than the major radius. 

Is there a supplier who provides custom sizes ? I even have a porthole glass but it's hardened...

 

[Peter Drew]

Coring is best done from both sides to avoid breakthrough chipping. 

[Merlin66]

Peter, agreed.... but when just cutting circular blanks it's not as important. We used to mount the blank (with a dab of pitch) on a spare piece of glass. This allowed the cutter to finish below the rear of the blank giving a good (but slightly tapered) edge. We made around 50-60 blanks for the local astro society.....