knife tempering question

[ilan]

Thought i would like to make a couple of knives from scratch so just to be a little different i wanted a bush crafty blade with a stick tang to make it lighter . I also wanted a taper on the blade so its thinner at the point i have now got the shape and thickness i want and will grind the edge on it (Nothing fancy just a flat grind) .
Now of course i have a blade with various thicknesses on it will this be a problem when i try and harden/ temper it ? presuumably the tang is left soft or do i treat the whole knife . ilan

 

[Shinken]

Flat grinds are reasonably hard to do! unless of course you are talking about scadi grind, which is easier.

And as for heat treating i am sure someone who is better at explaining than me will be along soon!

 

[C_Claycomb]

I am loath to get into the process of blade hardening since heat treating has been covered in huge depth over on www.britishblades.com, www.bladeforums.com or http://www.knifenetwork.com/forum/forumdisplay.php?f=1
If you are making a hidden tang, particularly a thin through tang, you want to leave the back end of the tang soft. Where the hard part finishes isn't of great importance (at this stage), though its probably better if you can get it to be past the blade/tang transition. If you heat it with a torch you will almost get this automatically.
I assume you are using O-1 tool steel?
If you are using O-1 and a torch your main fight will be in getting the steel as hard as it can go. Most likely you won't get full hardness on the quench, so a lower tempering temperature of 160-180degC will do and give you a workable final hardness.

The difference in cross section won't be a problem. Many knives taper along their length (called distal taper). The caveat is that you have to heat the blade evenly. Having taper means you have to heat the thick part a little longer, while not letting the thin part cool, or overheat. Its not a big problem, just something to be aware of. I usually found that having the tip grow too cool was more common than having it overheat, but that was with a one-brick-forge and Go-Gas torch. I am sure that a real forge would have been different.

 

[ilan]

Hi thanks for that i was going to use a bbq type forge and charcol how thin do you get the edge thickness befor begining the process / will be using 01 steel
Ilan

 

[C_Claycomb]

Edge thickness prior to heat treating varies a little. There are folks who take their scandi type edges down to nearly sharp, working on the idea that an 8mm bevel is a lot to grind down by hand in the hard state.

I guess it depends on how many times you heat the steel. If you only heat it once or twice, you can probably get away with a pretty thin edge, less than 0.5mm. If you are going to thermally cycle the blade, then I would go with the advice given me by various US makers to leave the edge at about 0.75mm. More work to grind down, but it means that you will have enough material to clear any decarburization before setting up the cutting edge.

You haven't said what grind you will be doing. Single bevel scandi, or full flat with secondary bevel?

What reference sources have you been using to get you up to this point?

 

[ilan]

err err pass ? brought a piece of steel bar from cromwells and filed it to shape and put on it the distal taper ? now starting to put the edge grind on it with a file was then going to temper it by getting it hot till its non magnetic then quenching in an old bath of engine oil then baking in the oven (when the wife goes out )
for the final treatment ilan

 

[C_Claycomb]

Everyone has to start somewhere

Since it is coming up to Christmas, maybe you can get someone to buy you one or both of Wayne Goddard's books, "The Wonder of Knife Making" and "The $50 Knife Shop".

Have you seen Greenpete's web site?
http://www.greenpete.co.uk/?page_id=28
It should give you some ideas of how to proceed.

Best of luck...if you clean the blade really well before tempering, the smell of engine oil in the kitchen should be almost imperceptible