Heelo guys,

Simple question. I am basically profile cutting 6mm and 3mm plywood and 3mm MDF with Scrappy my home made CNC, I am cutting with 2mm 4 flute tungsten carbide end mills at 500mm/min, 1mm depth per cut @20,000rpm on KRESS. The problem is I am getting through them at a rate of knots, they are getting hot and snapping off, is there a good quality bit that will last longer than 10 minutes.

Stewart

Gert a 2 flute bit, and increase the feedrate to 1500-2000mm/min.

Better yet get a single flute Onsrud router bit and really fly through that stuff. Consider a down spiral cutter so that thin material isn't picked up by the cutter.

Many thanks Gerry and Gary,

After a bit of a search I came across http://www.cncroutershop.com/uk_en/belin-single-flute-down-spiral.html, now one of these is more expensive than a dozen of the ones I have been using, so cheap is not always better!!!!!
Now I am going to show my ignorance now, feedrates I have now found out are important, using the formula FEED RATE = N x cpt x RPM the tool highlighted above will require a feedrate of 2000mm/min if I run at 20,000RPM, my poor little machine can just about manage 1000mm/min at a push, with the wind in the right direction. Will lowering the feedrate effect the tools performance/service life or can I just simply lower the RPM so the feedrate calculation will fall into my machines working envelope?

Sorry for being such a noob

Stewart

Stewart,
In wood I wouldn't worry too much about the feed rate being half of what it should.  You'll only see the full feed rate on relatively long moves because you have to slow down for every corner and if they are close together you won't ever get near the highest possible feed rate. I don't know where you are but these guys seem to have pretty good pricing:

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_solid.html

Lowering the feedrate while keeping the same rpm will cause the tool to run hotter, which will shorten it's life. As you've noticed, heat is the enemy of router bits.
If you cut the feedrate in half, you should lower the rpm by half, if you can. Be careful with small bits though, as they may not cut as well if the rpm get's too low.

As for good bits at low prices, try these:
http://www.ebay.com/itm/10-3-32-0938-2-FLUTE-MICRO-CARBIDE-ENDMILLS-Kyocera-Tycom-/381432400080?hash=item58cf2488d0

This is an excellent seller with very good quality products.

Many thanks for the info guys, really appreciate your input.

Stewart