Workshop Projects

December 31, 2011

 

Whittling Knife

After finishing my striking knife, and being very impressed by the excellent quality of the steel used in making good sawzall blades, I thought I would have a go at making another knife. This time, a whittling (carving) knife. I'm not much into carving (or knife making, for that matter), but I do some basic stuff occasionally. Anyone that is, will have a full complement of knives and chisels for the task and this type will usually be in there - often referred to as a sloyd, it's a general purpose knife, good for roughing and some detail work. It has a 2-1/4" long blade with a curved edge and a fine point:

The blade has a 'full convex' grind profile (no secondary bevel) which makes it well suited for carving and a snap to sharpen. The handle is sapele wood - I have a small piece of it that I've been using on small projects. I think is a great wood for knife handles.

I started with a small new sawzall blade:

Using an old one is fine, as long as it hasn't been bent or overheated, which often happens while using sawzall blades.

Grinding the teeth off:

I have water handy to cool the blade, to make it easier to handle. Also, since only the cutting edge of the blade is getting heat treated, it's a good idea to keep the blade cool while working it.

Grinding the profile on the belt sander platform:

And forming the bevels on the blade:

What I'm after is a gradual arc from the spine to the edge. The goal is to have a fairly thin edge with enough 'meat' behind it so that it won't be too delicate. This is the trickiest and most time consuming part of the project but worth the extra effort, in my opinion.

Some further shaping and smoothing with wet / dry sandpaper:

I want to remove the deeper grinding marks and smooth the transition to the tang.

Heat treating the blade:

I'm using a propane torch and this is less than ideal but should be adequate for what I'm trying to do: harden the edge and body of the blade but leave the rest in a softer, more flexible state. It would be nice to have a small forge for this and maybe someday I'll set one up.

Quench in motor oil:

Checking the hardness after, I found a file would not cut into the blade, so the procedure was successful. I then cleaned the oil off of the blade and put it in the oven at 400 degrees for about 20 minutes - this tempers the blade to relieve stress and reduces the hardness of the blade slightly. Hardness is great for edge holding but the blade has to have some flexibility as well - tempering does this and leaves the blade less brittle and resistant to breaking. Of course, this is pretty much guesswork on my part, since I'm not certain about the exact composition of the steel used for these blades. Still, it seems to be a reasonably close estimate, as the finished blade has the qualities I was after.
Cleaning and polishing the blade is next and I did this with 1000 grit wet / dry sandpaper and some water. Nice to have that perfectly mirrored finish but it's not strictly necessary and I only went as high as 1000 grit.

With the blade finished, I start work on the handle. I drilled a 3/8" hole into a piece of sapele wood:

I had a different idea for securing the blade in the handle that I wanted to try out.

I made a dowel from hard maple:

Using a 3/8" dowel maker to cut it.

I then split the dowel down the middle on my small band saw:

The idea is to have half of the dowel on each side of the blade tang and insert that into the handle.

Mix up some slow set epoxy:

I use a thin stick to coat the inside of the hole and the blade tang with the glue:

I then coated the 2 half dowels and slide these in beside the blade:

After letting it set for an hour, I trimmed off the excess:

The wood is very porous and epoxy squeezed through the end of the handle stock from the pressure of inserting the dowel:

The handle is sanded down to rough shape on the disk sander:

And brought to its final shape on the belt sander:

I stop to test the grip every once in a while. The handle has to be comfortable to hold and work with for extended periods, so getting it to the right shape for my hand was important.

Some hand sanding with 100 grit then 400 grit smooth it out:

A few coats of linseed oil are rubbed in:

The oil finish gives some protection but leaves the feel and texture of the wood.

A fair test for edge holding ability is to do some cutting and see if the knife is still keen:

Slicing easily through paper afterwards indicates a durable edge.

I made a short video of the whole experience:

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A practical project, one that I'm sure will see a lot of use over the course of its lifetime.

Thanks for reading,
John Heisz

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