[OwlCNC]

Hi All,

I'm trying to machine a rectangular pocket in glass. The problem I'm having is that the rectangle's perimeter is chipped along the edge (see picture below). I'm using this mirror for optical purposes, so the edge finish is important.

Attachment 236234


Right now I'm using a diamond coated endmill - perhaps there is a better tool for the job? Here are my machining parameters:

Material: soda lime float glass
Tool: diamond coated carbide endmill, 1/32" diameter, 4F (Niagra Cutter #DIA430)
CNC parameters

• 3000 RPM
• feed = 1 in/min
• cut depth = 1/64"

Any ideas? This is my first shot at machining glass, and I'm only making a handful of these for prototype purposes.

Thanks!

[awerby]

I don't think those are the right endmills for glass. Diamond-coated carbide tools take a much more aggressive cut, and are meant for relatively soft but abrasive materials like graphite, where the material quickly dulls a normal endmill. For glass, you want an abrasive tool. You can get diamond-plated cylinders ( a rod coated with diamond particles) inexpensively, or for more money, get sintered diamond tools that last a lot longer. But if you're just doing a few of these, the cheap ones might work. They usually come a little fatter, but you can probably find 1/32" diameter if you look around. Here's a place to start: Diamond Carving Points - Kingsley North Use them with plenty of water.

[OwlCNC]

I don't think those are the right endmills for glass. Diamond-coated carbide tools take a much more aggressive cut, and are meant for relatively soft but abrasive materials like graphite, where the material quickly dulls a normal endmill. For glass, you want an abrasive tool. You can get diamond-plated cylinders ( a rod coated with diamond particles) inexpensively, or for more money, get sintered diamond tools that last a lot longer. But if you're just doing a few of these, the cheap ones might work. They usually come a little fatter, but you can probably find 1/32" diameter if you look around. Here's a place to start: Diamond Carving Points - Kingsley North Use them with plenty of water.

Hi awerby,

Thanks, I thought there should be a better tool for cutting brittle materials. Do you have any advice on machining guidelines? Tool engagement, RPM etc.

[awerby]

Spin the tool as fast as you can - if 3000 RPM isn't as fast as you can go.Use flood coolant. Try the feedrate settings you've been using, which seem pretty conservative; step over about 1/5 of the tool diameter. A bigger diameter tool will go faster, but your corners will be rounder. You might try roughing with a 1/8" tool and save your 1/32" for a finish pass.