Hardening and tempering

[kevinlightfoot]

I managed to damage an auger for one of my hollow chisels,the spurs were damaged an it was blued,I have reshape the spurs and cutting edges and now I need to harden and temper the auger.It is a Clico chisel and bit and wasn't cheap so the metal is as far as I know good quality.Now as an apprentice many years ago I did a bit of this but my memory isn't so good so I need advice as to how to proceed I have the facility to heat the metal with a propane torch but I really don't want to spoil the auger altogether.Any advice woud be appreciated.

 

[Trevanion]

I'm not really sure if they're actually that hard anyway since they were pretty easy to file from new.

 

[--Tom--]

Hardening and retempering would risk knackering it completely. Scaling, warping, stress fractures on thin sections.
Not something I’d want to do unless I had no other choice and didn’t mind replacing it if it went wrong. Have you tried using it to see how it performs now?

 

[kevinlightfoot]

Thanks for you replies lads,I will try it today to see how it performs it now as sharp as it was when it was bought but I was concerned about its toughness,I will probably end up buying a Japanese style replacement from Axminster I think they are better than the Clico ones I have a few of each and the Japanese ones perform much better.I have also been looking at the Draper Expert ones but they are more expensive.Anyhow I will try the damaged one today and report back.Regards Kevin.

 

[kevinlightfoot]

Tried the auger this morning and it was partially successful,needed quite a pull to mortice a piece of softwood,the edges stood up well but I wonder if the cutting edge geometry may be slightly different after my sharpening.I don't use this tool very often but one of the jobs I got around to during this lockdown.I think I will still buy a new one and keep it as spare.

 

[hawkeyefxr]

To harden your auger depends on if it has any carbon in it, To check you can run a file over it near the tip, if it makes a mark it will be soft, if the file just slides over the metal and just 'polishes' the metal it will be hard, It may well be hard just at the cutting end. Usually something like that is not hard all the way along it's length as this is the strongest setup for cutting and twisting.
When you harden a metal you have to temper it back a little, First you get it red hot (make a little enclosure with bricks you propane torch will work a lot better) when its red hot dip it in clean cold water. You need to clean it then so it's fairly bright, reheat it slowly till the metal is straw coloured and dip in clean oil, this takes the hardness out of the metal and leaves it really tough.

Like you i did all this years ago in my apprenticeship when i was in the tool room making press tools. Hope this has triggered your memory a little.

 

[heimlaga]

I rekon it would be possible to harden only the tip.
Most ordinary steels reach hardening temperature right when the steel becomes unmagnetic on rising heat. I use a small magnet tied to an iron wire for testing this without burning my fingers.
If the steel is unknown I try hardening it in oil and if that didn't work I heat it again and try lukewarm water.

I am by no means a blacksmith but I have some basic tools for blacksmithing and sometimes make tools I need or dress old tools.