How to keep plastic fron wraping around your bit?

[knight_toolworks]

I have about 12000 holes to drill in some high quality polycarbonate. it does not melt on the bit. but the shavings tend to wrap around it then they rub in the surface. using a .052 but does not help since it is so short.
I did spray the plastic with some dry lube and that seemed to help. air did not really help or I could not run enough to cause it to work since the compressor would be running for 5 hours straight.

[harryball]

If the RPM's are low you might try mounting a small stiff bristled brush in such a way it contacts the bit just above the surface. Nylon might work, if not brass would be the next best option.

/RB

[harold_weber]

Steve, you simply need a different geometry on the drill point. You can buy drill bits specifically ground for plastics from Onsrud.

If you have a really good eye, you can re-grind your own conventional drill bits. You simply "dub" the cutting edge to produce a smaller rake angle. Just Google "dubbing drill bits". This will take practice. If you don't feel comfortable doing this, most machine shops have a person who is good at doing this, but I think they will tell you that for that small a bit, its less expensive to just buy the right tool and throw it out when dull.

[myxpykalix]

Steve have you called Fred over at centurion? Don't they have some type of "chipbreakers"?

[cnc_works]

Steve, call Multicraft plastics in Portland. They deal in acrylics, bits (usually Onsrud) and cnc work. Usually, I can actually talk with the cnc guy if the sales clerk can't help me.

Donn

[knight_toolworks]

right now I was using a .052 endmill. but I found circuit board drill bits solid carbide with a 1/8" shank for only 4.55 from mcmaster. plus they are longer so I will try them today if they get delivered. since the shavings did not stick to the 1/8" endmill I think it was just the shape of the bit since it is so small with such a big shoulder.
when dealing with such a small bit you don't have too many choices and .052 is a real oddball. a brush may be an idea if it is still a problem. not much room in there though with the bit so short. but the circuit board drill bit is longer so that may help.

[paulkiecka]

it might be too much of a hassle but you might try applying paint - mask the kind they sell at vinyl letter/sign shops. It could get scuffed up during milling then you just peel it all off.

[bearcat]

When drilling soft plastic I've used the Peck drilling option in the Drilling Toolpath to make short swarf that is then flung away from the bit.

Ed

[knight_toolworks]

Tried the brush but it did not do it.
peck drilling may work but with 12000 holes it would add quite a bit of time to the job right now it is close to 5 hours. I sprayed the surface with wd 40 and that seems to work so far.

[landdesign]

Steve I use WD40 too... works good. be sure to remember that WD40 uses Propain gas as a major ingredient. we don't want to hear about any sudden happenings in your shop

Erik

[knight_toolworks]

I will use a water based lube to keep cleanup easy next time. almost have the 12000 holes done on one bit.