cold chisel into hot chisel

[jawno]

I was reading on another thread that you shouldn't use a cold chisel on hot metal. The respondent said he was gonna make the cold chisel into a hot chisel first. I didn't want to pollute that thread with off topic discussion but my curiosity was piqued. I'm wondering if anyone could please tell me why you shouldn't use a cold chisel on hot metal and how do I turn my cold chisel into a hot chisel.

[Nakedanvil - Grant Sarver]

Other than the grind, I'd say the warning is probably because hot chiseling will harm the temper for cold working.

[Rich Hale]

It is about wot kind of steel the piece is made from. The short answer is that there are steels that actually keep there shape if you should over heat them, like in hot work. Two of those that I use are S-7 and H 13 They deform very littleif any even if they start to turn a little red when you are using them.
Cold work steels are made from steel that needs to be heat treated after being fashioned, Meaning they are hardened and tempered for the task they are intended for. If you get them hot when using to the point they start to show color the heat treating is gone and they are likely to be softer, think of mild steel at that point. My hot cut hand held chisels are quite thin behind the cutting edge, that concentrates the power I apply with a hammer so the cut is deep fairiy fast with as little work as possible. Cold chisels are not thin in this area and in use as hot cut will try and spread the cut wider open which makes it need more force to do the same task. If you have little outlay in a cold chisel try it and see how it works.

[ThomasPowers]

I often forge old cold chisels into hot tooling with no problem. They just don't work well to go the other way without doing a full heat treat on them.

[K. Bryan Morgan]

I believe I'm the one he's talking about. It would have been fine to "pollute" the tread. Its sort of a catch all thread about the whys and wherefores of forging anyway. What John had said to me was good advice. As it turned out we didn't reforge the chisel and it worked out just fine. As we worked, the chisel became more and more the shape you would normally see in a a slitting chisel. We didn't dress it. As a consequence, the longer we used it, the better it worked. Would I do that again? Most likely not. Johns advice was sound. If I had done as he suggested I believe our slitting job may have gone smoother. Using an inexpencive, relatively speaking of course, chisel, and turning it into a hot cut chisel is a good way to go. It saves work and time. I'll be getting more of them and using them for hot work. But, I will defer to those who have more experience in the future and grind or forge to a more hot cut friendly profile.

[John B]

Cold chisels are for use on cold metal, and are a steeper angle than the hot cut/chisels is what I inform my students.

Cold chisels can easily be sourced from various places, car boot sales, second hand shops, or engineers suppliers, as opposed to hot cuts which are more specialist 'smithing tools. They are usually octagonal in section which used to be the standard identification for a good carbon content tool steel., so this gives a known base to work from.



You can modify cold chisels by reforging them into hot cuts by forging/slimming them down, and altering the cutting angle to a more acute one so it slices through hot metals, and then allow to cool, grind the edge and you are ready to go, cool frequently when being used.



Cold chisels are made for cutting cold metals, and if used as a hot cut, the cutting angle means you will have to use more energy in use, and you will also by using it on red hot metal, remove the tempering at the chisel point, which then means it is not usable as a cold chisel anymore until it has been re heatreated including tempering for the task it has to do.

[John B]

Thanks KB, I was composing the above as you posted. clarified and confirmed what we were talking about originally

[ThomasPowers]

Trust but verify! I've run across several pieces of octagonal; stock that wouldn't harden; enough so that testing a bit is standard before I let a student use on in the forge.

One of my hardies was made from a jackhammer slitting bit that had broken a couple of inches from the end. I forged out the broken end to fit the anvil and then forged down the edge a bit as well as I like a sharp hardy rather than a blunt one.

[jawno]

Thanks all for your replies. This site is a great resource for information. And yes, it was the posts from Bryan and John B in the other thread I was referrring to when I asked the question. Again, I appreciate the clarification.