hot chisel

[BORZ]

i would need some help about material for hot chisels.What i have yet, i made of an old drill,hss material.Although the heat treating is a challenge(im not experienced in smithing),it succeeded so far,that the piece didnt break,and able to use.What material is ok,(junkyard,used stuff),and how to treat it?Possibly not the most difficoult way:rolleyes:.Thanks for help in advance

[Walking Dog]

Borz -
A good junkyard material for hot chisels would be automotive or truck coil springs. They typically run 3/8 - 3/4 inches in diameter. Forge your chisel at colors from bright, almost lemony, orange down to bright red, then reheat to continue forging. Let it cool when you have nearly the edge you want. Heat it to non-magnetic and set it aside on your ash heap to cool slowly to room temperature. This is normalizing it to relieve the forging stresses. Heat again to non-magnetic and quench it in warm oil. It should now be quite hard and brittle. Use sandpaper to shine up the working edge by removing the forging scale. Then take a blowtorch and heat the struck end and shaft as uniformly as possible to about 500 - 600 F. Let the heat run down the chisel to the cutting edge. When the cutting edge runs colors from yellow through magenta just turning purple/blue, put it in the water bucket and cool it. This should leave the working end adequately hard, and the struck end soft enough to be tough. At this point, use your file or grinder to dress the working end. If you use a grinder, don't let it get hotter than the same magenta/blue that you heat treated to.

This process has worked for me to make reasonably good chisels and punches.

[BORZ]

thanks very much for help'Think ive got some of the piece somevhere,about 1.5 cm.thick. Ill try the process next,and give info about the success(i hope,success)!
Thanks again

[ThomasPowers]

Another step up is to use hotwork or other steels that have high hot hardness, like S7 or H13 which will maintain their hardness even when jammed into glowing steel during use.

Unfortunately not generally found in the scrap stream though sometimes you can run across smiths selling pieces for such tooling.

[philip in china]

I make my chisels out of 1"rebar then just treat as described above. The rebar I got happens to be very good stuff. If you have unidentified junk yard steel the secret is to experiment. If it is too soft just try again. My first chisel I had to try a couple of times before I got it right. Nowadays the manual workers here are always coming to me to have new chisels made or old ones rehardened. I know nothing on the subject really but use the experience I have accumulated.

[John B]

Another useful source for hot chisels are old worn files, thicker the better,(Old farriers rasps are ideal) I hot cut off the tang end about an inch or so down the blade, (I use this bit to make a handy little scraper for removing welding spatter or paint etc ) and then anneal (normalise)them

After annealing, forge the cutting edge to the shape required (flat or curved) sharpen with a hot rasp or whatever, then heat treat this edge by quenching in oil/brine then polish it and draw the temper, this can be done in whatever way you wish, I use the forge or a gas burner played on the top end of the chisel and chase the colour bands down to the tip, quenching at a purplish heat

The danger with using the file as a blank is when it is in use, keep the cutting edge cool. I like to dip it in tallow, if you leave it in contact with the red hot workpiece there is a danger that the tip gets warm and if you then cool it in the water trough/bosh it will make the end brittle again

[stretch]

After the hardening and when you are tempering the wider the color band or the slower you draw the temper the better. To narrow of a color band the more likely you will have a fracture point in the tool and could break off easily. Heat the struck end, not to much, or the way I do it is only dip about 1 to 2 inches, when hardening, into the cooling liquid and when all the red heat color is out of the unhardened part take it out and polish the hard end and turn it with hard part up in a vise and let the heat you want reach the end and quench the whole tool. It usually runs real slow and have had great success for a number of years now. It speeds up the process too. I take most tools to a straw color, sometimes light straw and sometimes to a dark straw.

[philip in china]

Forgot to mention......... of course if you are making a hot cut chisel or a hot cut hardie for that matter hardness does not need to be extreme. A cold chisel needs to be much harder. Hot steel is easier to cut.

[Ice Czar]

Hot steel is easier to cut.

of course how much cutting and how hard your cutting has a lot to do with how hot your chisel will get and if it will reach an annealing point. We do a lot of chiseling with impact hammers, and even though the chisel steel is quite good, its still advisable to have multiple chisels and a quench cup to keep their temperature down, makes the inevitable resharpening and retempering sessions further apart.
(the cup isnt quenching the steel you don't let it get that hot, water quenching embrittles the chisel, which breaks it, we retemper with oil. The cups are just to disperse the heat its gained on a pass before its set aside to await its next turn)

Conduction of heat dramatically increases with the temperature differential, dwell time, but especially the contact pressure. An illustrative experiment is a pan of water on a stove top, as its is just beginning to boil, add downward pressure to improve the contact, then let up.

This isnt generally an issue with chisels not mechanically assisted and used only occasionally, my example is more the exception than the rule. We will chisel a few hundred balustrades for twisting at a time. (four sides, 10 inches of deep chisel lines per side, 58" to 1.25" stock) Thats a lot of heat transfer in a sustained manner.

[BORZ]

guys,thanks much for help!Unfortunately i cant make it yet(quite heavy rain this time),but if i come to it,i'll say how it went.Thanks again!

[Glenn]

Borz
Go to the top of the forum page and click on user cp
click on edit profile
go to the bottom of the page, enter your location, and save.

We would like to know where in the world you are located.

[Phil Dwyer]

We will chisel a few hundred balustrades for twisting at a time. (four sides, 10 inches of deep chisel lines per side, 58" to 1.25" stock) Thats a lot of heat transfer in a sustained manner.

Wow, that's a lot of chiseling. Thanks for your description of using an impact hammer, multiple chisels rotating in and out of a an oil soak holding area for cooling. You must have quite a sizable (and toasty) operation. You must indeed be an Ice Czar if you can keep from melting around all that heat!

[Ice Czar]

we use water for the cooling, and oil for retempering which even with rotation is just a matter of time.

The other two tricks are a jig to hold the stock since the impact hammer tends to drive it out of a basic clamp setup. It needs to be something you can work quickly to keep down the number of heats. The second trick is an extension handle to the chisel to control it's direction.

5/8 stock isn't that bad, but as the cross section of the stock increases the amount of thermal mass and the total radiant energy increases, to the point that Ive been burned through a single uninsulated leather glove by 3/4 stock from 4 inches away (the hand holding the extension). Wrapping another glove around that hand as a heat shield solved that problem.

(1 inch stock has 4 times the thermal massenergy of 1/2 inch)

[BORZ]

Ok,i tried give my lokation.Few things i dont understand,but im on improoving my english knowledge.Sorry

[Ice Czar]

no need to apologize
I can't manage to make two languages stick (and I've tried)

to help you with English, it would be

Ok, I tried to give my location. Few things I dont understand, but I'm improving my English knowledge. Sorry

[BORZ]

Thanks,i guess i have now all the knowledge,just have to put in praktice somehow.About the material- am i wrong with the old drills(hss)?I have some,18-25 mm(about0.5-1""),but i've red about the heat treating,wich doesnt seem easy.(though i made one,even if not the proper way,but it still vorks).Is it reason experimenting around,or rather leave it.An old file i have as well,for triing

[Ice Czar]

Frosty's replies in this thread
http://www.iforgeiron.com/forum/f7/woodworking-chisels-drawknife-5242/
is a really good description for tempering

what I do at work with the impact chisels is quick and dirty tempering that isnt going to last very long because of how they get used. Speed is more important than how well the chisel is tempered, we just run the color up to a blue with an oxy-acetylene torch and oil quench it. Its more important to be working, than to be messing around with the tools to do the work.

Drill bits, files and spring steel are all good candidates, Im working on making a bunch of gravers from various scrap

[Ganoksin] Jewelry Making - Gravers
[Ganoksin] Jewelry Making - Engraving tools and preparation- Theory and Practice of Goldsmithing -

so I too am looking at doing a long lasting and good job of tempering which is why Frosty's posts where so helpful ;)