Milling Glass

[trent_julie]

Hello,
I am part way through a project, I was wondering if anyone has had success milling glass. I hope to make a small hole through an existing mirror. I would be happy to hear any tips.

Trent

[Billyboy78]

It's quite easy, you can use a piece of pipe of a suitable length and diameter with wooden circles fixed to the top half with a bolt to grip in the drillpress. You then feed the pipe gently onto the mirror using #80 grit and water at a slow speed. Go dead slow as you near the other side for fear of bursting out a chip. A better way is to make a jig for the mirror, then grind 7/8th of the way through then turn the mirror over and attack the other side. If you're making a Cass you would polish out first before breaking through on the front side. A diamond holesaw will be quicker but more expensive, hardly worth it if you are going to make only 1 hole.

Tip...cut 4 slots into the cutting face so the water/grit can circulate.

[Wilso]

Small diamond hole saw drill bits are relatively cheap to buy now.
Have used them to drill hardened ceramic tiles.
Readily available tile and tool stores.

Good luck with your project!

[Merlin66]

We successfully used the method suggested by Bill many years ago when we supplied many mirror blanks to the amateur community in S Africa using a stock of porthole glass we acquired for nix.
Softly softy and constant attention is the way to go.

[Rod]

Hi Trent

Be aware that cutting a hole will release stresses in the glass and ruin the figure on the mirror you have. It will need to be re- figured at the very least.

If you go ahead, I would recommend diamond tipped hole saws. I got some from eBay a few years ago. They work well and are inexpensive, just use plenty of water.

It's easy to to take a chunk of glass out on the rear side as the bit comes through so cut to within a short distance of one one side and then turn the mirror over and cut in from the other side.

Rod

[trent_julie]

Thanks everyone for your guidance, as suspected there will be a challenge. Once again the iceinspace community has proven itself a wealth of knowledge.