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I previously worked on Virtual Reality and other hardware at Valve.  I currently work at Google[x].

Prior to starting at Valve, I built computer peripherals such as keyboards, mice, and joysticks that were designed to be used inside MRI machines.  My company, Mag Design and Engineering, sold these devices directly to researchers at academic institutions who used them to publish scientific papers in peer-reviewed journals.

After work, I spend time on many different types of projects that usually involve circuit design, machining, material selection, and general fabrication/hacking.  My favorite place to be is my home workshop.

ben dot krasnow at gmail




Monday, August 22, 2011

CNC milling glass plates and mirrors

I've been cutting glass plates and mirrors with my CNC milling machine machine for years. In this video, I describe a few tips and the general technique that I use.

Clamping the glass plate to the table is the critical part of the process, and so I built a jig that allows the glass to be held laterally with shims, but does not require a high clamping force, which would crack the glass.

Cutting parameters:
.085" dia diamond burr
3000 RPM
1-3 inches per minute feed
Cut depth .130" (full material thickness)
Flood coolant with soluble oil cutting fluid

Older post: http://benkrasnow.blogspot.com/2008/08/cnc-milling-glass-plates-and-mirrors.html


  1. Thanks for the tips on milling ("burring"?) glass!

    Also: Hey neat, an R2 E3, same as mine! I removed the Boss8 controller and replaced it with a Linux PC running EMC2 (www.linuxcnc.org), and I couldn't be happier.

    1. Hi,

      could you please share your knowledge, if i can do the same on Chinese desktop cnc router
      please mail me on shubhanshu.jain@gmail.com

  2. Funny, I had searched the web before on cutting glass with a CNC and never came up with anything either!

    I'll 2nd EMC2, I use it on a Linux PC as well for my Taig Micro Mill.

  3. CNC waterjet cuts glass easily like butter. But be warned that the glass must not be tempered.

  4. Ben-

    I was just thinking. two ideas: 1, a double-sided adhesive film to stick the glass to an aluminum plate or whatever mounting base. If the adhesive is an issue (breaking the glass trying to remove it), you could also (idea #2) have a thin film of soft material with a high coefficient of friction (but not adhesive) to put between the glass and mount. drill holes in the mount as air passages, and then get a shop-air powered vacuum generator to draw a vacuum on the passages. The glass would be held on by the pressure differential.

  5. David, I use double-stick tape very often for machining plastic plates. It works great, but often the coolant will cause the tape to come loose, so it's best used dry. Also, as you anticipated, getting the mirror or glass off the tape is sometimes a big problem (if it doesn't come loose due to coolant seepage). Seems contradictory, I know.

    I've never used a vacuum chuck (what you described in #2), but I would like to. It requires careful setup so that unused holes are plugged and air doesn't leak in. It gets a lot more difficult when using a cutting fluid, but still possible with a fluid trap. Vacuum chucks work well with paper-mask plastics like acrylic. It's possible to program the depth of cut so precisely that the plastic is cut through, but the protective paper mask is left intact, providing a seal for the vacuum system.

  6. I wish I had thought of this when I was cutting a IR filter very similar to what you have there, only thinner.

    Looks like you have a Erickson Quick-change spindle.

    Don't get the Ajax. I have heard nothing good about it. There are several options out there for retrofitting and keeping the existing servos and drives. I have done several retrofits/builds and recently installed new servos on my mill:


  7. Hello,
    First of all, your workshop and machines are amazing.

    Second of all, old heavy nc/cnc machines are better then modern lightweights.

    Third of all, give up at servos. It is good when you have big machine for mdf or acrylics. For this machine, strong stepmotors with current choppers and microsteps driver will be enough + ubuntu emc2 and that is all. Here http://www.youtube.com/watch?v=PmewmV87Lcg&feature=player_detailpage is an example of modernization old mill to cnc with usage of emc2 and steppers.

    Think about vacuum holder with rubber gasket like this: http://www.youtube.com/watch?v=9K9ylKWUHKE&feature=player_detailpage it doesn't need to be this hight but it is helpful when you cut throw the material.


  8. Hi,

    could you please share your knowledge, if i can do the same on Chinese desktop cnc router
    please mail me on shubhanshu.jain@gmail.com

    1. I don't see why it wouldn't work. You can cut glass with a diamond burr in a handheld Dremel tool. Even small CNC machines can do it.