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@peteski - can you recommend a source for that little wonder?
I usually get this type of stuff from either McMaster Carr or MSC Industrial, but you can find them on eBay or probably amazon. But as I mentioned, I don't remember if it needs to be 82 or 90 degrees for exact match to the screw head.I have both 82 and 90, and also a 60 degree (all 1/8" diameter) for cleaning axle dimples in truck sideframes. You can never have enough tools or bits. https://www.mcmaster.com/countersinks/number-of-flutes~1/material~carbide/Actually they are now more pricey than I remember (I bough mine years ago - they last forwver when used on soft materials), but even at $15 they are still well worth having.
The J I Morris screws linked to earlier are 82°. Ideally the countersink should match the screwhead, so you'd want an 82° countersink. The idea is that the sides of the head are in contact with the whole countersink, rather than just one point on it. None of us are going to get any benefit out of a coated tool. I'm not sure there's much benefit from carbide over HSS either. Carbide is better in a lot of ways, but if we're making chamfers in plastic by hand we don't need those benefits. They're also more expensive and chip more easily. My workbench is usually a mess and a HSS cutter will last longer in that environment than a carbide one will.
