Machining Fire-Retardant MDF

Fire-retardant-treated MDF is much tougher on tools than ordinary MDF. Here's some info and some suggestions for tooling. November 15, 2010

I'm looking at a largish job that uses veneer on a fire retardant MDF substrate. Is fire retardant much harder on tooling? With standard carbide compression cutters, about how much can I expect their life to be reduced? Also, are there different types of fire retardant MDF, some more receptive to adhesive than others? Is there a brand that is better than others?

If machining is likely to be a big problem, I wondered about trying an intumescent clear coat over standard veneered MDF as an alternative approach.

Forum Responses
(CNC Forum)
From contributor M:
First of all, I don't run the machine, but I take care of the programming and tooling. I can only say that based on tooling used, the fire retardant particleboard is pretty tough on tools. I'd say if you figure about half life on your bits, you'll be fine. Both the particle core and MDF fire rated materials are tough on tool life. We don't lay up veneer here, but we haven't noticed any problems with the veneer adhesion or performance when fire rated material is specified.

From contributor G:
We are currently cutting a commercial job that calls for fire retardant plywood and just finished three smaller jobs that required fire retardant MDF and/or water resistant MDF (an outdoor storage shed, patio cabinet and cooking stations for "The Garlic Fest", which we donated). I program, run and maintain our CNC and did notice a little bit more wear and tear on the 3/8" compression bit. I changed the bit out about 15 sheets earlier than I normally do.

From contributor J:
One of my suppliers has recently come out with a tool that might be good for this application. It is an insert compression bit that allows for carbide inserts or diamond inserts or a combination of both. The idea is that you can use carbide inserts where carbide is most cost-effective and diamond inserts in the most abrasive areas, like an abrasive veneer or laminate where you tend to get wear lines. The diameter is 20mm for single-flute or 25mm for double flute.

From contributor R:
We see a carbide tool only last 20 to 50% as long in fire MDF as regular MDF. The thickness makes a big difference due to dust removal. We went to diamond bits and got about 12x the tool life of the carbide tooling.

From contributor C:
What you have is a very tough application. We have the very hard carbide that extends the wear, but I would like to see you try some of the coatings we are trying, including diamond film coating.