Wooden Spokeshave, Part 1: The Iron

For far too long a time, my shop to-do list has included, "make a wooden spokeshave".  Finally I got to it.  Mine is very similar to Bob Rozaieski's design, but has some details I'd seen on other spokeshaves as well.  I've made two of them now, and these posts will go back and forth between the two builds.

The first thing to do is to make the iron.  I've had a piece of 1/8" thick by 1 1/2" wide O-1 steel that I got from McMaster-Carr, and the packaging shows it to be by Starrett.  My iron was to be 11/16" wide in the middle with a 3/8" x 3/4" tab at each end.  It'll be 4" long (including tabs) and the blade portion will be 2 1/2" long.  I started with some layout.

Laying out with a square and the scribe tool that comes in most combo squares

Then hacksawed and filed to the lines

Filed the bevel, but not all the way to a sharp edge 

Used the hand grinder to get to about a 0.020" flat at the edge

What it looks like so far

Now here's a detail that I was a little unsure about.  In the pic above, you can see that I still have about 3/32" to 1/8" of steel between the heel of the bevel and the line where the tabs start.  Both the Hock and Lee Valley blades have no extra steel there at all.  That means the first time you sharpen their blades, you're also removing metal from the fore edge of those tabs (depending on your sharpening method).  That just didn't seem like a good idea to me, so I used steel wide enough to leave those extra few 32nds there.

Next was to drill and tap holes in the tab ends for 12-24 threads.  I've only ever drilled metal a handful of times and until now, I'd never tapped a piece of metal.

Made a crosshair 1/4" from the end, centered in the tab's width

For the second blade, I put the hole 1/16" closer to the end.  This gave more room for the blade adjustment set screw hole that I'll describe later.  After hitting the crosshair with a center punch, I drilled an 11/64" hole, using a wooden 90° block to help keep the bit straight.

Drilling the hole ...

... and tapping the hole

This went well, though I forgot to use a little oil when tapping the hole.  Only going through 1/8" of metal made this easier.  My holes wandered a little bit.  I don't remember if I drilled initially with a smaller bit and graduated to 11/64" or if I went directly for the full size.  But if I did use more than one bit, I can see how it might wander.

Now that the blade was prepared, I needed to harden and temper it.  And here's where the problems started.  The business part of this blade is 2 1/2" wide and 11/16" deep.  I use a propane torch to heat the steel to the right temperature (to where it is non-magnetic), I need to keep the flame focused on one spot.  When I move the blade across the flame to get a more even heat across its full width, I just can't get the whole thing to the proper temperature.  Well, I did the best I could and then tempered the blade in the 350° oven for about 90 minutes.

Starrett shows the hardening and tempering temperatures on the label

After sharpening the blade and trying it out in the partially built spokeshave, the edge crumbled.

Cutting edge looking horrible

Close-up of above pic

My understanding of working with steel is that I now needed to hit the reset button for that blade and that means annealing.  I'd never annealed anything before.  From what I've read, you heat as if you're hardening, but let the steel cool very slowly.  Some websites quote a rate of no more than 70°F per hour!  No way I'd have the equipment to control that.  And I don't even have a charcoal barbeque, where I could use a hair dryer to stoke the temperature, get the blade to cherry red and then leave it in the coals until the whole mess cools down naturally.

After some research, I bought a couple of K-26 fire bricks that I hollowed out to create a little furnace.  There's a wire screen in between the bricks that the blade rests on and the torch enters through a hole carved out in the side.

This pic is staged - I did this step outdoors

Well, as cool as this looks, I still ran into the same problem that I had before - only a circle about 1" in diameter got to cherry red, right where the flame was focused.  But again, I did my best, then placed the iron in a large pot filled with vermiculite to let it cool "relatively" slowly.

In the mean time, I went out and bought a MAPP gas torch.  To re-harden the steel I used both torches and this time I got it to non-magnetic before plunging in oil.  After tempering, it seems like the blade is a bit better.  Maybe not perfect, but better.  At least the edge is not crumbling like before.

Well, that's all for now.  Next time I'll get into the woodworking.