[How do I?] What Part Of A Tap Is Hardened?

[rwm]

I want to make a cutting tool out of a broken tap. What part of the tap is typically hardened? The entire tap or just the thread cutting part? Could I use the square drive end for a cutting tool.
Thanks in advance.
Robert

 

[chips&more]

That’s a good question. If it’s a good quality made tap, I believe whole thing is hard. Give it a file test to make sure.

 

[hermetic]

The whole of the tap is high carbon steel, or tool steel which has been hardened, then tempered (perhaps) to give it some spring, but as we all know, they will snap! you can grind to any shape, and then re harden if necessary, or soften, grind, and then re-harden. If they are "HSS" you can grind and use as is, but do not aliow to overheat during grinding

 

[Andre]

HSS can take overheating just fine, it will technically change minutely but you'll never notice any difference. That's one of it's character traits.

 

[Bob Korves]

You can heat HSS to dull red with no changes whatsoever.

 

[Kernbigo]

Hss taps are hardened in a salt bath or a vacuum furnace, and drawn back to 62-64 rockwell

 

[george wilson]

Yes,it is nearly impossible to ruin the temper of a HSS tap. They are tempered at 1000 degrees,which is a good red hot heat. Tony Wells said he has melted them down and the cooled puddle of HSS was still hard as could be!

 

[strantor]

That’s a good question. If it’s a good quality made tap, I believe whole thing is hard. Give it a file test to make sure.

I'm no expert on taps but I spent a good deal of time making knives in the past. For a knife you want a good high carbon steel, and you harden the cutting edge, or do your best to harden only the cutting edge, and leave the spine unhardened.

That gives you a good edge that doesn't dull, and at the same time the blade still has good strength. You can use the knife for prying, without worrying about the blade snapping and sending shards of 90 Rockwell death flying at your eyeball upwards of the speed of sound.

I distinctly remember looking on in wonder at the way my blood skated across the sheen oil on the shop floor, with a cordless drill in one hand with half a tap chucked up in it, and the other half of the tap sticking out my other arm, and thinking "man, I really shouldn't have put that harbor freight tap in the drill. They probably hardened it all the way through. "

I know (now) the difference between a machine tap and a hand tap, but still, I would expect that any tap flying the flag of "good quality" would be hardened in a similar fashion as a knife; that is, not all the way through. But I could be wrong.

 

[Andre]

I know (now) the difference between a machine tap and a hand tap, but still, I would expect that any tap flying the flag of "good quality" would be hardened in a similar fashion as a knife; that is, not all the way through. But I could be wrong.

I don't think there would be a reasonable way to only harden the outside of a tap and keep the inside cool. Even if you managed to keep the inside soft and more flexible, the outside would still crack and chip at the point of breakage, jamming the tap into the work instead of just snapping it in half making it more difficult to remove.

 

[eeler1]

Dunno bout that, that's what case hardening is all about. cant say if it applies to commercial taps