> the feed speed needs to be fairly slow!
I think on *any* rotating-tool cutting, you start with the feed just fast enough to finish one "today".
That usually gives a nice cut.
You turn-up feed when you get an order for 10,000 "today!" Making cars was a lot about speeding-up feeds to cut a lot of cast-iron and turn out a lot of cars on existing machinery. But you are not in that situation (yet).
Yes, slow feed can be trouble. My warped table-saw will burn the wood if I feed slow, less if I go fast. But that's poor guidance from bent fence and my un-smooth hands. At the other extreme, high feed rates often demand very beefy spindles and arms to damp the least shake; and of course sharp tough bits.
You don't "need" diamond to cut soft copper or board. You may want carbide (maybe diamond) when you cut a mile of traces and plain-steel cutters go dull too fast for your taste. But unless I am cutting hardened steel or worse, I always start with tool-steel tools, wait until I blunt a few before investing in fancy-stuff edges. (I switched to carbide round-saw blades a long time ago, but I'm still on plain steel chain-saw teeth because I don't blunt that many chains.)
