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Large conical drills to use as drifts ?

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Hello Guys;



I was given a box of 33, 35, 40 and 45 mm drills; mostly new, some chowdered up. MK3 and MK4 tapers. I can only use them in my lathe (MK3 tailstock). I have nothing with MK4. And the bucket contains 50 drills.

I always assumed these were HSS; or M2 tool steel; and as such brittle and not suitable for hammering. Then I found one with a chowdered up tip, but what struck me is that the taper had some dents. Like someone hammering on it.  The "drill" end of this thing is really hard and will readily chip if struck; but the taper part is soft.

So I figured, lets give this a try, I cut it up and made a cute round drift. Guess what; it actually holds up pretty good, and the top even mushrooms (without splitering or cracking). It behaves like 52100 or 9260, it doesn't move much under the hammer at all, but being a drift and being already in that shape, it doesn't need to either.

So I'm puzzeled .. the drill end is most defenitely HSS (it's written on the drill, manufacturer: cleveland) , but the taper part, is that still HSS ? Somebody is probably going to tell me this is a bad idea - and I agree, I was expecting to be attaching pictures of shards of steel and  a cracked drift, but nope. 

So.. altough this is probably a bad idea, why does making round drifts from the taper part of huge drills actually work?

greetings, Bart

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You could test the drill bits in several different ways. (These work for saw blades as well, as some are bi-metallic.)

Take a sharp, new file and try to scratch a line across the bit to shank transition at intervals. If it gradually goes from hard to soft, only the cutting part is hardened, and the tang was left soft on purpose, just like a file. If a sudden transition, different metals used for bit and shank and welded. 

Or, you could clean, polish and etch part of the bit to see if there is a color transition between the tempered cutting end and the shank.

And of course, the crude blacksmith way: heat it up to forging temp and see if it shatters when you hit it on the anvil. If not, they may be useful cut down as hardy tools, with the shank squared up to fit the hardy.

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