I really think you missunderstood what I wrote. Carbide came about because we developed metals that ate up high speed tooling. You found yourself sharpening the high speed tool six to eight times a day. Softer, or less tougher materials didn’t really benifit from carbide. Yet at the sametime the actually sharpening (or creating a cutting tool) of tools was becoming a black art. The younger you are, the less you learned about surface cutting speeds and tool shapes because there was inserts in a plastic box. Add to this, much of the older machinery was never designed for carbide or ceramics. Reason why is tool pressures. Carbide is known as being on the high end of the scale because it doesn’t cut material; it just pushes it off. High speed for the most part shears the material off in a knife like fashion. Tool pressures are far lower (this has many advantages)
Originally there was maybe one or two grades of carbide, but now there are many. Even carbide with diamond impregnation. You ask if carbide was bad for drill holes in plastic. I don’t see where it’s needed personally. Plus carbide anything is usually much more expensive. Your not cutting a pre heat treated steel or something seriously tough. Plastic doesn’t work harden like some metals do, so I see little if any advantage except to the seller. What I would recommend is the use of TIN coated drill bits (the gold colored ones) or cobalt. The latter is a couple three points harder, but doesn’t shatter like carbide. And it’s cheaper. Hole quality will be the same; I hate to say. One issue with plastics is the material getting hot and melting. I’ve seen folks use strait water, and hand soap. Bees Wax is supposed to be the best (have never tried it). The idea is to keep the plastic from attaching itself to the cutting tool. I do know that bees wax gives a better finish, but as I said I’ve never used it. Then we usually find ourselves relying on the good old pin vise (I do). The material never gets hot because we are going too slow actually.
if your buying drill bits from a large seller, then tell them you are cutting plastic! Normally the lead angle and relief are for steel. Plastics need something different. They’ll cut better. Those real small drill bits are not really meant to resharpen, so you just toss them (or reuse the shanks for pins). I would like to see how they grind them! As for lubricant; I’ve had good luck with liquid Dawn cut 50/50% with water. There’s better but also costly.
gary
