Working Fiberglass Reinforced Plastic on a CNC

Tips and cautions for machining FRP on the CNC. Choose bits carefully and beware of the dust. October 25, 2007

I have a client that wants me to cut sheets of 3 mil fiberglass reinforced plastic. I guess it comes in 4 x 8 sheets and he has assured me we can cut it on the CNC machine no problem. All we have ever cut on our CNC is plywood, MDF, hardwood, and Corian. I have no idea what I should do for tooling, and then cut speeds. Does anybody have experience cutting this type of material?

Forum Responses
(CNC Forum)
From contributor B:
Fiberglass on woodworking CNC machinery is possible, but it is messy, tough on tooling, and tough on the machinery and people operating the equipment. There are special tools available that look like deburring bits that do a good job. Don't expect anywhere near the tooling life you get with wood machining. The dust gets into and on everything, it is abrasive, and will work its way into and through your skin, and lungs, and anything else if left unprotected. It does the same thing to everything it can penetrate on the machine - pads, pod, seals, wire insulation, whatever, you get the idea. Tread lightly, and if you can't get a premium for the work, you might want to pass. You might want to pass anyway.

From contributor E:
Whoooo boy! Like the posting above. Special tooling, short life, and I hope you have a serious dust collection system! Make sure the customer is willing to pay accordingly.

From contributor M:
As always, contributor B's advice is right on the money. At a former employer (about 15 years ago), we were cutting similar material. Ours was 1/4" and 3/8" thick. The tooling we used was a little more specialized for the application, and if you take the work, you may want to consider using this type.

The tools were little more than a tool steel dowel that were impregnated with industrial diamond chips at the business end of the shaft. They essentially looked like coarse grit sandpaper. Talk to your local tool supplier about them. I don't think you can get these off the shelf. The real thought with this tooling is that the tool life goes well beyond anything you can buy off the shelf.

From contributor G:
Use a fiberglass tool. CF series with us [Courmatt]. They come with a variety of end cuts, such as a drill style, end mill style, burr style or a fish tail type style. It will leave a lot of dust. I suggest using air to assist in chip evacuation.

From contributor D:
Dremel sells a fiberglass cut out bit in 1/4" shank. You can get it at Home Depot or Menards. It's a prickly bit made of solid carbide. I use a similar bit in 1/2'' with a bottom bearing for roughing swanstone solid surface, which is a mineral and fiberglass based material. Been using the same bit for years; they last a long time.

From contributor J:
I have been routing fiberglass for 18 years. I use a drill point burr cutter. You're cutting 3mm, which is about .118" thick. I would recommend 1/8". You can get away with a 3/32", but depends on how much cutting is involved.

From contributor C:
It's like everyone else has said - the fiberglass or burr bit is about the best choice. Tool life will be an issue no matter whose tooling you use.