Some Newbie Advice Re Identifying Bits Please!

[jwhitten]

Hello,

I am still a relative beginner to wood & metal machining. I have already built one CNC router a couple of years ago, and I am in the process of building my second now. So I have some experience with it, enough to make me dangerous, most likely ;-)

I have some questions that I was hoping someone here could either answer, or at least point me in the right direction for more information...

I have been purchasing el-cheapo bits here and there and they've been working out reasonably well. I've only broken maybe three or four bits over the last couple of years so hopefully I'm doing something right... I've amassed a fair collection thus far, and I'm trying to figure out how to identify them all.

That said, I know what an end mill is, and a ball mill, and the like. I know the difference between and upcut and a downcut bit-- and some basic idea of why you would use one or the other in a given situation. I know what flutes are and how to count them. I know the difference between a left-turn and a right-turn bit. I know what V-bits are, fly cutters, etc. So I can generally identify those in broad terms-- but that's not really my problem...

How do I tell the difference between the "good" ones and the "cheap" ones, once I've already gotten them and they've become just another bit in the box?

And what is my best strategy for (economically) moving up to better bits. Buying them used off ebay in estate sales? Just biting the bullet now and then and buying one brand new?

Does it even matter if all I'm cutting is wood and aluminum?

Once they're out of the package, how do I tell the difference between say, a regular (el cheapo) bit, a High Speed Steel (HSS) bit, a (Tungsten) Carbide bit, a Cobalt bit-- and is there any better kind of a bit?


My interests are in woodworking (cabinetry and such) and robotics / automation. That was what/why got me into all of this.


Thanks for any words of wisdom you might have to offer!!


JWhitten

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[widgitmaster]

HSS (High Speed Steel) is heat treated Steel, they work OK in mild steels, non-ferrous metals & wood.
Cobalt is yellow in color and holds an edge longer than HSS
Solid carbide is many times better than cobalt & HSS, but its brittle & brakes real easy! Carbide comes in several grades, C1 being the softest, C5 being stronger & tougher, C7 and better is used in hammer drill bits to cut through stone!
The el-cheapo carbide is usually too soft, and loses it's edge too fast!
Re-ground or Re-sharpened bits can be problematic, as the cutting edge geometry or relief angles aren't always correctly done! Too thin an edge breaks down, too thick an edge can''t take fast feed rates!

Widgit

[ger21]

With a router, carbide are the only bits you should be buying. HSS is rarely used in woodworking, as it doesn't last long at all.

How do I tell the difference between the "good" ones and the "cheap" ones, once I've already gotten them and they've become just another bit in the box?

Keep them sorted and separated, don't just throw them in a box.

And what is my best strategy for (economically) moving up to better bits.

Good bits are expensive. Buy new, quality bits as you need them.

Does it even matter if all I'm cutting is wood and aluminum?

Don't use the same bits for both wood and aluminum. Same goes for plastics. Would will dull bits faster than plastics and aluminum, and you should not use any bits that have been used on wood to cut aluminum.

Ideally, for aluminum, you'd want to get some "O" flute bits. Single fluted work well on routers.

Once they're out of the package, how do I tell the difference between say, a regular (el cheapo) bit, a High Speed Steel (HSS) bit, a (Tungsten) Carbide bit, a Cobalt bit-- and is there any better kind of a bit?

Good bits will have part numbers on them. Other than that, there's no easy way to tell two carbide bits apart, unless the quality is vastly inferior.