if cutting on a cnc,use a canned peck cycle this will retract the tool as set by parametier. i.e. cut forward .020
retract .002. this will at least give short chips.a very high positive tool works best. good luck

khirn, thanks for the idea but, i'm embarrassed to say this job is set up on a machine so old that the Z still has a half reading dial. i concocted a hook in the top of the tool so i can at least aim the ropy swarf into a catch bucket. it's better but, the stuff gets a static charge and clings to everything. i bid on this job thinking it would be a cinch--guess i'm just an "old metal guy". thanks, chip.

You will probably get the most detailed information on machining PVC from the Technical Service Report TSR 38: Machining Geon® Vinyl, from PolyOne.  You can obtain it from them using the following link:

http://www.polyone.com/tsr/index.asp

The rest of these sites offer varying degrees of information on machining PVC or other plastics.  Good luck.

http://www.harvel.com/PVCCPVCshapesmachine.html

http://www.bayplastics.co.uk/product%20guide/DSM-guidenavbar/prod-DSM-instruct.htm

http://www.pmfmagazine.com/magazine/archives.html

http://www.signweb.com/fabrication/cont/machining0900.html

TVP,
thanks for the info. i'm on my way there.
chip

How about another approach - I've used a vacuum to suck the chips immediately up. A vacuum venturi (check out http://www.anver.com or http://www.exair.com)and some clear tubing works well for smaller machines.

Hi,

I suggest to use a high positive radial rake.
www.iscar.com

When I am machining plastics like pvc, uhmw or similar I find that I must frequently interupt the cut thereby creating short curls that do not wrap around everything. There is no chipbreaker that will work on these types of plastics that I am aware of and when you consider the nature of what you are cutting I truly doubt that such a thing is possible. A chip breaker after all does require a degree of brittleness in the chip itself to achieve the breaking of the chip.

thank you all for the great ideas. as it stands now, i've angled my tool so that the ribbon is directed into a container and it seems to work quite well as long as my aim is good and i have no interruptions[of both the mechanical and mental kind]. thanks again, chip.