Thread: Hardening Steel

Agree - its pretty good for the Knowhow website.
It would also have been good to include annealing

Couple of other things.
If the object is short, one issue to watch out for is the wooden handle catching fire.
It might be better to use locking pliers or similar.

If the object is large and full hardness is required throughout the object then a small fame like an oxy might not be able to get hot enough for long enough.
One of the blokes at the men's shed found this out when trying to make knives from files.
This is where a simple small firebrick castle can work to reduce heat loss.

Really not a bad step by step. If people start with water, crack an iron, then try brine, crack an iron...they might go a little nutty!

The details might cause a bit of a giggle, though, like the cutting style torch with the back and forth on the long chisel,

I wonder if wikihow is the later replacement for the old "expertvillage" on youtube. We used to laugh at their videos, though some were a big dangerous (like a guy felling a tree and obviously without much experience). But I'd imagine they were the ones laughing all the way to the bank because they were raking in ad views in the early days of youtube when ads paid a lot.

The tutorial there looks like it might've been generated by computer aggregation.

The principle of the video is fine, but I would add a couple of comments. A small torch will, as BobL said, only work on very small items as you can't get enough heat into the object quickly enough.

I have used oxy acetylene in the past, but use a minimum of a No.15 cutting tip or preferably a heating head, which uses a huge amount of gas.

If you are quenching a thin or narrow object such as a small chisel ( 6mm - 10mm) or a knife, quench using a plunge action into different parts of the quenching medium. Don't stir as distortion of the the tools can occur.

If you are using oil as the quench medium, be prepared for it to catch on fire and have either an extinguisher of heavy blanket to hand. A little while back I made up a largish froe and even with 20 plus litres of oil it still lit up each time I plunged the tool into the oil.

Old leaf springs are a good source of high carbon steel for a range of tools, but to shape them and work them they need to be annealed initially. If you have a wood fire for winter heating you can put the leaf spring (or other high carbon steel) in there when it is stoked up high and leave it to cool down with the fire as it burns down overnight.

Regards
Paul

Originally Posted by Bushmiller

....If you have a wood fire for winter heating you can put the leaf spring (or other high carbon steel) in there when it is stoked up high and leave it to cool down with the fire as it burns down overnight...

Useter do that with old spent files, when I had a wood stove - worked a treat to anneal them, alright!

Interesting what you say about not stirring long, thin objects like chisels. I did just that with a chisel I was trying to harden and it came out like a banana - would've made a beaut bent chisel, 'cept the bend was the wrong way.

Hardening is generally not so difficult if you have an adequate heat source, and let's face it, if you are serious about working metal, you really do need a forge. My problem was (& still is), in tempering. Being color-blind, I can't see the critical colours for the right degree of hardness, so it's a real hit & miss affair. I've got a couple of drawer-knives I made from old leaf spring and by sheer fluke, I managed to get them just right. I reckon it would take me weeks to get them as good as that if I had to do it again!

Cheers,

Ian

The light straw colour comes really quick. I have found that if you think about whether the colour is light straw or medium straw it goes blue as my brain struggles to find the right gear.

Perhaps you could use a heat gun to measure the temperature. They probably don't cost much compared with days gone by, but I haven't looked into it.

I made largish draw knife for my son from a leaf spring and even with a heating head it was difficult to maintain the heat right along the blade. From memory I think it was 10'' or 12'' long and quite deep.

Regards
Paul

Just on the subject of using old files for tools, it is probably worth mentioning again that they are unsuitable for any tool subjected to stress. The classic example of this is wood turning tools: A real no no.

All the teeth need to be ground off a file when recycling them as they create line of weakness in the steel. That can be quite a chore so often there is not much mileage in using them. Having said that, I made some stubby screwdrivers from a file for removing saw nuts: Fine for that type of application.

Regards
Paul

Originally Posted by Bushmiller

Just on the subject of using old files for tools, it is probably worth mentioning again that they are unsuitable for any tool subjected to stress. The classic example of this is wood turning tools: A real no no.

All the teeth need to be ground off a file when recycling them as they create line of weakness in the steel. That can be quite a chore so often there is not much mileage in using them. Having said that, I made some stubby screwdrivers from a file for removing saw nuts: Fine for that type of application.

Regards
Paul

If old files are annealed is is really easy to removed the teeth with a bench grinder or even a flap grinder.
Then if they are hardened and tempered correctly they can be used even for turning chisels.

Bob

I expect you are right in what you say, but for me the risk is just not worth while, particularly when leaf spring material is so readily available (car wreckers, friends and family etc). There was a rather graphic video posted a while back on the Forum about what happens when a turning tool made from a file goes wrong, but I'm not sure if it is still available.

I have access to a surface grinder at work to remove the teeth from file and I still would not trouble to do it. The other issue is that once the teeth have been removed the metal is substantially thinner and no longer has quite the potential.

Ok, I'm a wimp .

Regards
Paul

A used leaf spring is more likely to have developed micro-fractures making them dangerous for turning tools. I'd rather spend the time removing teeth from a file and heat treat it than use a used leaf spring for a turning tool.
Of course new steel is rather cheap (at least here in the U.S.).

ron

Originally Posted by Bushmiller

Bob

I expect you are right in what you say, but for me the risk is just not worth while, particularly when leaf spring material is so readily available (car wreckers, friends and family etc). There was a rather graphic video posted a while back on the Forum about what happens when a turning tool made from a file goes wrong, but I'm not sure if it is still available.

At the mens shed we have demonstrated to the newbie woodturners how easily a file will shatter and how a file that has been heat treated and had its teeth removed won't. This is done not so much to convince members how to make lathe tools but to not just grab any old file and make a tool out of it.