Cold Chisel

[Gordon]

Hello, the next idea iv had for a wee project is to make a cold chilsel.
Im going to make it using a suspension spring (spring steel, around 6% carbon is that right?)
Straighten it and then heat and quench, any ideas as to how many times i should heat and cool it?
Also any other ideas to try and make using this technique. would a screew driver work? or a small knife?
Its more just for the experence than pratical application, but still no reason not to put it to good use.
Any suggestions welcome,
thanks

 

[R Kraft]

A simple explanation would be.
To make steel soft you heat it to red and cool it slowly.

To make it hard you heat it to red and cool it quickly, in oil or water.
It will be glass hard and brittle.
If you heat it a little you will make it softer, but less brittle.
So basically you heat it to red, quench it, and then heat treat it according to what you will use it for.
Lots of info on the WWW.
http://www.nasascale.org/howtos/termpering.htm
Robert

 

[irondarren]

making chisels is quite a serious job, i have made a few in the past using en8 and en16, with reasonable results. hardening and tempering is a complicated issue. it needs heating to a dull red, then quenching in or oil or water. this hardens it, but to temper it you need to reheat to a much lower temperature and hold it there for a given time.
http://www.westyorkssteel.com/

interesting info about tempering, hardening forging temperatures there for given materials like en9 en8 en16 etc

 

[bill_gj]

You might want to try your local library to see if they have any old workshop technology books - the sort that used to deal with the basics for apprentices.

These always used to have a tempering colours table. These are the oxide colours that appear on a bright piece of steel when heated - before it gets to give off light (dull red, cherry red, yellow, etc).
They are a range of colours, like a rainbow, and correlate to certain temperatures and can be used to estimate how tempered a piece of steel is after hardening.

So - harden by heat & quench
Clean and polish the part
Reheat (temper) until the edge you're interested in gets to the right colour, then quench again.
Have a look at:
http://members.optushome.com.au/terrybrown/HeatTemperChartEtc.html
http://www.tpub.com/steelworker1/11.htm
........and.......
http://www.alexdenouden.nl/08/temper.htm
....this last one gives an idea of the use of a tool and the colour to temper it to.

Normally, when tempering, you heat a portion of the part that is a little away from the edge you need tempered and then you can watch the oxide colours creep along.

Sorry if I am teaching you to suck eggies.

 

[Gordon]

hello,
Thanks for all that info, very helpful, changed some of what i was thinking.
Cheers

 

[Gordon]

cold chilsel finished

Hello, i finished the cold chilsel, thanks for all the help
it seems to have worked, although i over heated a small part of the tip the first time i was tempering it and it just broke when i started to cut the steel plate i was using to test it. but i just used the grinder to cut the edje back a little more to get past the weekend part.