How to heat-treat/temper steel?

[Flexibel_kampfe]

I have a set of High Carbon Harbour Freight Chisels(woodworking type) that I mistakenly recked, using an angle grinder to sharpen them... I didnt realize once it heats up, then its lost its temper...

So my question is: Whats the best way to temper steel? I dont have much in the way of heating tools... but I do have a wheel around fire pit, and a pyrotechnical thumb(dont we all.. ) So I figure I might be able to do something...

Is there anyway to do this without a torch, or blast furnace..?

Planer shavings and linseed oil?(Linseed oil is flamable as all hell.. and planer shavings are slow burning..)

 

[devino246]

Go buy a propane torch at Lowe's for $20. Very handy to have around and a new bottle of propane is only $3.

 

[Flexibel_kampfe]

I would.. but my budget is kinda maxed...

 

[devino246]

You need something with a directed heat output.

 

[Flexibel_kampfe]

What about sticking in in a can(filled with something) I know thats how sometimes people make mini-blast furnaces... They usually add a torch.. but I think thats to keep it lit..

 

[devino246]

What about sticking in in a can(filled with something) I know thats how sometimes people make mini-blast furnaces... They usually add a torch.. but I think thats to keep it lit..

Id get some charcoal, light it(in a safe place & not on concrete), let it burn for a few minutes till it glows without a flame, then take either an empty can or a small clay flowerpot and place enough charcoal in it to fill it halfway. Then either, A: drop the chisel(with the handle removed) in the can/pot, or B: cover the top with some sheet metal (16ga or thicker), leaving a small opening and hold the end of the chisel over the opening. That should get you some good heat. As far as heat treating goes, im no blacksmith. Google

 

[Flexibel_kampfe]

Im in for method B: I do not know if I can remove the handles... they are PVC...

I might just bury the chisel in halfway... Since its only the cutting edge that needs to be hardened...

 

[tundrazach]

do a little research on heating and quenching steels. Quenching it in oil vs. water makes a huge difference. It would be best if you can find exactly what steel they are made of. Also, a lot of heat treating processes require heats of 1000 degrees Fahrenheit and more.

Be very very careful the first time you use them after heat treating. Theres a good chance that you could turn the metal into one (yes its actually a different grade of steel when HT) that is so hard its brittle and can shatter when struck with a hammer. Do your research before you stick them in a fire, and you have a greater chance of not ruining them further.

Next time sharpen with a file to avoid getting them hot.

Edit: are you using these just for wood working? They may be fine to use on wood still. Just may need sharpening more often

 

[DirtTrackRacer_07]

I have herd, but not tryed, Heating it till it turns orange with a torch and sticking in a 5 gallon bucket of lard or sand and let it slowly cool.

Im not sure if it tempers the steel but it hardeneds it from the extra slow cooling.

 

[Flexibel_kampfe]

Someone on a woodworking site told me they are now useless... so Ill take their word on it...

I might try the linseed oil soaked shavings.. that should provide some heat...

 

[tundrazach]

I have herd, but not tryed, Heating it till it turns orange with a torch and sticking in a 5 gallon bucket of lard or sand and let it slowly cool.

Im not sure if it tempers the steel but it hardeneds it from the extra slow cooling.

when you heat metal, it changes the crystalline structure of it. it changes quite drastically at certain temperatures, thus making the steel have much different properties and strength characteristics. If you let it cool down slowly, the crystalline structure will slowly got back to nearly what it was before (depending on the metal) and you can lose most of the benefits of heat treating. Most times you have to quench, submerge the red hot metal, in a bucket of water, oil, or some other liquid to bring the metal down to room temperature rapidly and lock in the crystalline structure of the high temp steel.


To the original poster, In my Machinery's Handbook, there is almost 50 pages on heat treating steel. If you get me the exact type of steel that those are made of, I beleive I can find what temp, and what cooling process would be best for you. You also might be able to find a digital copy of this book online. I know I had one before my HDD crashed over the summer.

 

[Flexibel_kampfe]

http://www.harborfreight.com/4-piece-chisel-set-42429.html

Those are the ones... It just says "High Carbon" So my guess is "Ultra-High Carbon" "1-2%" (cited http://en.wikipedia.org/wiki/Carbon_steel)

 

[Cam]

Someone on a woodworking site told me they are now useless... so Ill take their word on it...

Useless for metal maybe, however wood is soft -

and bendy and knoty and flamable and uhhhgggg blah don't use it

Sharpening a chisel is pretty straight forward, you need a bench grinder with stone wheel, and a container of water beside it.

hold the chisel upwards to the grinder so that the handle is down towards the floor, softly and slowly grind away your rake angle dipping the chisel end in the water every few seconds, don't let the chisel end get blue hot, when its red its ready to be quenched in water, when it gets this hot you are ruining the hardness - im sure you get the jist.

Now thats how you should have sharpened it, your best bet would be to grab a coarse file, clamp the chisel in the vice and file the rake back till it becomes hard to file, because unless you have managed to heat up the whole chisel blade, only the end would have lost its hardness

be careful with the file and don't rush it, you slip off the blade with it the chisel, it could cut ya.

What are you using the chisels for? like i said i wouldn't worry if its wood.

Cheers, Cam.

 

[Flexibel_kampfe]

I let it turn blue... opps... I did it on an angle grinder with a flap disk, because I dont have a bench grinder(relative said I could borrow theres..but they are in Vietnam for a couple weeks.. so thats a no-go...)

I took it off every couple seconds 2x/min atleast.. and quenched it... it ususally hissed, so I know it was hot...


I use the chisels for everything from chopping Mortise and tennon to carving(I specifically ground one of the small chisels I dont use to a very shallow bevel for carving... thats one reason I didnt do this by only stone/sand paper... ) I also use one of them as a beater... prying nails(up enough to get something better under it..) and screwing things...(generally screws.. have to keep your minds from wandering... lol)

 

[Cam]

Ok, the ones used for carving/mortise i would just carefully resharpen using the technique above just with the angle grinder, grab a F/g clamp and lightly clamp the grinder to the bench, disk upwards and unwind the handle (keep the guard on though!) wear gloves and prop your hand up on wood and holding the chisel handle (gloves away from disk!) apply same technique.

For the beater i would just clamp it in the vise and file it back a few mils into the shape your after, guessing your using it a munty chisel i wouldnt be too worried.

Whatever you do, don't throw them away they are still good for something.

Cheers, Cam

 

[Flexibel_kampfe]

I had to take the guard off.. its bent.. so a screw on flap disk wont fit. It also poses an in-running nip-point.

Thanks: Will do.

 

[devino246]

Ok, first off, as cheap as I can be, there $6!!! can you not scrounge up some cash and go get another set? Second, these are wood chisels, not multi-tools. Use a chisel to chisel wood, a screwdriver to screw fasteners, and a prybar or catspaw to pry up nails. Inappropriate use of tools can lead to destruction of the tool and harm to you or your property. Woodworking requires the right tools. Its only 6$ for this set of carving tools. I understand not having access to large sums of money, but dont go out and buy exotic wood, an ATV, or big pieces of machinery when you cant afford the simplest of hand tools.

 

[Flexibel_kampfe]

I didnt say I did HAVE money... I have about 1500 still left from working.. but I want to save as much of that as possible for insurance and such..

I want to try my hand at fixing them before getting another set... although I am, to have a set of scary sharp, non-beaters...

 

[Flexibel_kampfe]

Screw it... I tried doing it with plane old fire... all that did was make me smell of smoke...

Im out to get a blow torch tommorrow... since as it is, I have to spend another $200 for a Graphics Card, since mine burnt out... and the darned company went out of business, so their lifetime warranty isnt worth the ink they used to write it...

Whats better: Propane, or MAPP? The MAPP kit is $30 more than the Propane, and $40 more than just the brass torch.. but is it worth it?

Also, do you need eye protection, such as with OA, or is this mild enough not to need it...

It says you can weld with MAPP, is this true? Or merely braze?

 

[devino246]

Just get propane. The extra heat output isnt worth the extra expense.

No need for eye protection. Very little light output.

You cant weld with pure mapp, only with mapp & oxygen. You can solder though.