Heat-Treating Drawknife?

[Jacob Reverb]

Hey, all,

I just bought a drawknife on ebay. It's fairly sharp but nowhere near where I want it, so I began the chore of sharpening it.

It originally had a straight 10" edge, but from years of use and sharpening it now has a bit of a "belly" in it.

I rigged up a jig to hold it at 30° so I could begin bringing the high spots on the ends down and thus begin to straighten the edge. However, when I tried to file the high spots down, the file wouldn't "bite" at each end of the edge -- only in the middle where the steel was softer.

My theory is that someone along the line somewhere took a grinder to the edge, got it too hot in the middle, and drew the temper out of it.

My question is, once I get the drawknife back in shape with a flat back, a straight edge and a 30° bevel on one side of the edge, can I then heat treat it to harden the softer steel back up, and if so, how?

What Rc hardness should a drawknife typically be?

And what temperature/time would I need to heat treat it to get that hardness?

Thanks in advance for any advice.

Jacob.

[Robert Loss]

My theory is that someone along the line somewhere took a grinder to the edge, got it too hot in the middle, and drew the temper out of it.
Could be, but many drawknives are made with a differential temper although it's usually across the blade so the spine temper differs from the cutting edge. I think it's usually tempered so it is harder on the edge and the spine is tempered slightly softer to better take a shock so it won't shatter so easily. This sounds opposite to yours.


My question is, once I get the drawknife back in shape with a flat back, a straight edge and a 30° bevel on one side of the edge, can I then heat treat it to harden the softer steel back up, and if so, how?
Try this site http://www.iforgeiron.com/forum/f7/woodworking-chisels-drawknife-5242/#post47080 . because you don't know how your knife has been treated, you should also re-anneal the whole thing first, presumably you can remove the handles?


What Rc hardness should a drawknife typically be?
One sees numbers like Rc52 used but you can go as high as you like but then you will need to use a grinder to sharpen and treat it gently otherwise it might shatter, or softer but you will have to sharpen more often.


And what temperature/time would I need to heat treat it to get that hardness?.
That really depends on what type of steel it is. 1450F is a typical annealing temperature and then tempering can be done by surface colour or if you have access a furnace and use a temperature probe which is how I do it. Heaps of info on the web about how to - just search around. Unless you know what sort of steel it is you might be wasting your time although I guess it depends what you paid for it - you might have nothing to lose by trying.

Here is a drawknife I made from and old file, brass plumbing fittings for ferules and some jarrah off cuts for handles. I retempered at it work to Rc58 using a temp controlled furnace. How do I know it's Rc58? because we also have Rc hardness testing gear! :D

[Jacob Reverb]

Thanks Robert. That's another interesting forum ... I think I'm gonna need a bigger shop! :p

[Johnny Kleso]

If you heat treat it you will get a funky rust on the steel and it will need to be reground..

I heat treat plane and marking knife inron in my back yard and would not reccommend you doing yur drawknife
https://home.comcast.net/~rexmill/heat_treating/heat_treating.htm