Grooving Planes 3 – Wedge and Edge


One final task remained before final glue-up of the plane bodies – the wedge had to be roughed out.  I had saved a small piece of ebony for this purpose, and began by making a rectangle of appropriate dimensions.

Grooving Plane 11
The plans specified a rectangular footprint of 3 ¾” x ⅜”.  I added ⅛” to the width to allow for the kerf and trimming, and cut the rectangle on the diagonal with the bandsaw to make two wedge blanks.  I put the blade in place in the open body and inserted the wedge in position.  I used 120 grit sandpaper flat on the benchtop to smooth out any irregularities in the wedge and get a good fit to the channel.

It’s important to identify the individual wedges, and not get them crossed up.  No matter how much care you take to make the planes identical, there will inevitably be some variation in cavity geometry, and the two wedges probably won’t interchange.

The original plans called for the end of the wedge to be rounded with a finger grip scoop, which is a very classic look.  However, past experience has taught me that, while ebony is very hard, it also has a tendency to be a bit “chippy”.  This indicates to me a certain brittleness.  With this in mind, I decided against any complex shaping of the end of the wedge.  Instead, I simply rounded over the front corner and sanded everything smooth.  This provided a large, flat tapping surface, and the wedge shape was easy enough to pull without a finger grip.  The last thing I wanted was to shear off part of the wedge while tapping with a mallet.

Grooving Plane 12
Once the fit of the wedges is suitable, the other side of the plane can be glued into place.  Be sure to wax the channel surfaces to prevent glue from sticking, and clean out any glue squeeze-out before it dries completely.  The iron blank works quite well for this purpose.

Now, it was time to turn my attention to the iron.  This was the part I had been dreading, since I had never heat-treated steel before.  It actually turned out to be much simpler than I feared.  Since the steel was O1 (oil-hardening), it was simply a matter of heating the steel to cherry red and quenching in oil.  With larger blanks this can be quite involved due to the amount of heat required and the dynamics of the way it moves through the steel.  However, with these ¼” irons, most of these factors didn’t apply.  I was even able to use a regular propane torch – something that was out of the question with larger irons.  My basic guidelines came from Peter Berglund’s website page: “A Woodworker’s Guide to Tool Steel”.

I set up my equipment on a metal tool chest and rolled it to the middle of the open shop bay.  This put me under a 18’ ceiling well clear of anything flammable.  Outside is recommended, but with just a propane torch, I really couldn’t afford the airflow from the wind.  For a quench bucket, I used a tin can from the kitchen filled with used motor oil.  Not seen is a metal lid to cover the can if the oil caught fire.  I realize this isn’t much of a risk with a small piece of steel, but better safe than sorry.

I had already narrowed the irons slightly to give a touch of clearance as they passed through the channel in the plane body.  Also, I had flattened the back and ground a preliminary 25 degree bevel on the WorkSharp.  I left the edge very blunt to avoid any focal points while heating – just formed the basic shape of the bevel.  These operations were much easier while the metal was still soft.

I did the hardening in near-darkness to see the colors better.  No pictures, sorry.  That would have required two more hands and a tail.  It was a simple matter of holding the iron edge-first in the heart of the flame.  As the front part heated up, I eased the edge down and out to balance the heat and color over the wide part of the blade.  This sounds complicated, but becomes self-apparent the first time you do it.  Just watch the colors.  Once the wide part of the iron hit bright cherry red, I plunged the iron edge-first into the oil, moving it up and down rapidly to even the quench.

Grooving Plane 14
Tempering came next, and was easy as pie – literally.  I simply placed the irons in a 350 degree Farenheit oven for one hour.  I think 90% of oven recipes bake at 350 degrees – and steel does too!  This, according to the charts, would yield a hardness of R62-64 – perfect.  All that was left was a regular honing with a 25 degree primary bevel and 30 degree secondary.

All the parts are ready to go now.  Next time, I’ll put everything together and tweak the setup.  Stay tuned!

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