Originally Posted by
studioso
hi,
Forget about coolant, not necessary for plastic.
I'm assuming you are cutting HDPE. it will be really hard to get a perfect finish. you should however get chips, not shavings. definetly switch to single flute, use 2 flutes only for bits over 5/8.
I cut only plastics at my place. I've tried MANY onsrud cutters, upcutting, downcutting, from 1 to 4 flutes: I was never able to get a finish free of chatter marks, the way I can get it with styrene, ABS or acrylic. I use an 5'x12' AXYZ router, maybe it's over the machine's limits.
but if you are getting these fines, the filmy stretched cuts, you need to increase the chip load. a good sharp knife will allow you to slow down the motor considerably without harm.
BTW, drilling is a different story: you will often get these bird's nests wrapped around the bit as you plunge. this will often ruin the finish of the rest of the cut and prevent chips to properly evacuate. either clean it by hand after the plunge, ramp the cut sideways, have the bit retract often during drillng (peck drilling), slow down the plunge rate A LOT, or - for plunging operations alone- onsrud 70-500 plastic drill bits are beautiful. basically they are simple drill bits ground to a very sharp point (maybe like a 60degree?). these will give you some really satisfying curls...
good luck!