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recoton
06-26-2007, 06:37 PM
Has anybody got any advice for me i have been using key cutters to start with and didnt have any luck.i know there is no geometry in a cutter like that but that was how they did it before i started working there.So what i wanted was a
staggered tooth milling cutter but it would have to be cut down,because i need
.102 and i can only get .094.So instead i got a metal slitting saw with side clearance which has carbide teeth on both sides,But it still sticks to the material around the cutters teeth.Cutting a piece of plastic shouldnt be this hard to
work with,I tried different speeds and about 300 rpms it didnt work to bad but still melts the material a little.the best way i found to do these parts was to run them on the circular saw,which runs 3 times faster than the bridgeport i using the slitting saw on.so would you think that a staggered tooth cutter would work better than a side chip clearance cutter?Anybodys experience on this matter would make my life a lot easier.thank you

Geof
06-26-2007, 07:02 PM
Part of the problem with carbide is that the cutting edge is rarely razor sharp. With plastics that means you get a bit of deformation, the plastic sort flows around the cutting edge a very tiny amount so it rubs, gets hot and melts. I suspect the reason circular saws work is because they are running so fast the plastic cannot deform around the cutting edge it just gets cut cleanly.

You could try taking your speed up and also use a good feed, several thou per tooth. However if the plastic is not held rigid this may put a lot of load on it and bend it.

Use a lubricant, I have found liquid soap either straight or mixed 50-50 with water works. You have to be careful using cutting fluids becasue some can react with the plastic and cause crazing.

Another lubricant that I have used is beeswax, just rub it on the (stationary) cutter.

DareBee
06-27-2007, 09:20 AM
Yes, plastics should be cut with properly sharpened HSS.
I usually machine plastics (including polycarbonate) with full flood coolant.
High feed is definately required.
If you are just cutting it up - I use table saw, radial arm saw, circular saw and shear for all my guard panel cutting.

coltons customs
06-27-2007, 11:10 AM
i use a hss also and agree with the lubricant beeswax has always been my choice for plastic

recoton
06-27-2007, 06:28 PM
I cant really use coolant because i am doing it on a bridgeport and some of the
lexan i use has a paper coating,also its for lockheed martin and its cannot have scratches of any kind.i found that the best speed for the 3 inch saw was
300 rpm i did have it a lot higher and it melted really bad.Im also pretty sure i took the set out of the cutter,now the beeswax idea hopefully could help
because that would'nt be noticed,so if i can get some i'll give it a try.thanks for all your help its hard to find many people who cut a lot of different plastics.
the shop i work for does about 90% plastic products and i have been there for a year now and have machined some plastic in my 20 years experience but it has mostly been done with metal products.

chan luci
07-02-2007, 05:54 AM
Having cut lexan for many years, I can say one for sure. These sheets come with masking film or paper, never ever remove them till the last drop of cutting is out. This is the only way you can avoid scratches. As for cutting letters are concerned, fret saw (like your sewing machine, a thin wired saw goes up and down) which is fed into a predrilled hole runs across the sheet and the machinist should hold the letters damn strong as well as turn the sheet to the need of the design as well. (That's why I compared this to a sewing machine). If Lean is cut for machine part, then high speed low feed is the best way out with bee wax as lubricant on to the cutters.
Regards