Today I cut a reamer in half...

Like twist drills and other HSS chucking tools, they are generally of composite manufacture, a carbon steel shank welded onto a HSS "business end", they are not annealed; if one looks at the procedure for annealing or even partially annealing HSS, it is not even reasonably possible to accomplish. Heating HSS up to a full red does not remove more than a few points of hardness, this is what makes HSS such a wonderful thing, it will continue to cut when the tool tip may glow faintly red if the feed is sufficient to land the chip back from the very edge of the tool.
If HSS tools including drills and reamers were made of all HSS and the shanks were hard, a drill chuck could not grip on them sufficiently to drive them for a normally heavy cut, reamers maybe, drills, never. Besides,HSS is too expensive to waste on the shanks.
 
benmychree said:
Like twist drills and other HSS chucking tools, they are generally of composite manufacture, a carbon steel shank welded onto a HSS "business end",
Click to expand...

Learned even more today! Very cool. I haven't found any reference to that process online, but I completely believe it.
 
I had a broken bolt and tap extraction shop for years. And I made round chisels out
of old used drills. I would buy them at a surplus store by the pound. I would cut the flutes off at the end of the spiral . Then grind a cutting angle on the base where the flutes ended. That part of the old drills were still hardened but the shanks were not heat treated so I could hammer them without them chipping . I would drill the center out of broken bolts too the thread root. Then these Spẹcial round chisels were used to pull what was left of the bolt out of the mating part. Often I would get the first thread pulled away from the wall and then grab that thread with pliers and pull and it looked a spring coming out of the hole.
So my thinking is drills are hss that are not heat treated all the way to the shank end.
 
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