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Odd metal hardness

Awl--

Went to cut a worn-out caster the other day to salvage the balls in the bearing raceway, and was shocked to find that my 4x6 bandsaw simply skated over the shell -- the sides that are formed/bowed, that eventually contains the axle for the wheel.

Looked like run of the mill galvaninzed soft steel, but which seem tough as concrete nails, with a rockwell!

Whazzup?? Is this some kind of special alloy, for strength? Hardened too? Seems like overkill on a pretty light duty small caster -- I think it came off an old stereo cabinet or such.

I also found out the hard way how hard speaker magnets are -- ruined the not-so-cheap blade on a 16" DoAll. :( In particular, this was a black ring surrounding the yellow-zinc back, which I think houses the "main" magnet, which is what I was after. Didn't hardly dent this black ring, which "looks" super-soft.

Beware!

Reply to
DrollTroll
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The race was probably a case-hardened pressing. Figure out the loading on the contact points and you'll see why.

Magnets have to be hard or they wouldn't be magnets. Just one of those things. You've found that out. Only meaningful way to machine them is by grinding, forming them before sintering or machining the preforms. You can ruin the magnetic properties by trying to machine them after they're magnetized. At best you'll end up with a load of magnetic shrapnel.

Stan

Reply to
stans4

Put torch to that "yellow-zinc back," and it will pry off. It's just glued.

Reply to
sethro

The bearings have to run in a hardened race or they will destroy the race.

:-)

Remember -- the balls are pretty small, so if the race is not hardened, the balls will be pushed into it.

That black ring is the ferrite magnet -- it is a specialized ceramic, and thus is *very* hard.

Enjoy, DoN.

Reply to
DoN. Nichols

Well, it was the side of the caster, going down toward the wheel that seemed to have been hardened.

But, your explanation may be correct, as they proly harden the whole thing, or at least enough of the surrounding area where I was trying to cut.

One expensive week fer saw blades -- and end mills. sheesh....

Reply to
DrollTroll

snip

-may not be a good idea to use a torch: the 'yellow' could be cadmium - nasty stuff.

Reply to
Chris Holford
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Keep an old file around to test things before you try a sawblade or an endmill on it.

Hmm ... there are carbide grit hacksaw blades -- you could probably use one of those to cut most of the way down to the axle, and then split it with a chisel (while it and the chisel are wrapped in cloth to keep chips out of your eyes, and the balls out from under the bench.

Good Luck, DoN.

Reply to
DoN. Nichols

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