When we started Nice Ash Planes, all the woodworkers we talked with assumed we would go the normal route, buy premade irons and drop them in our plane. Nope, we decided to learn a bit about metallurgy and then tackled that bear ourselves. The real trick is in the heat treatment, but more on that later.
Our steel comes from the original steel state, PA. It shows up to our shop as 1/4” by 36” flat ground bar stock. Each bar will produce 10 blanks. The first few blades were cut with an angle grinder and then shaped from there. This process would be fine, if we were making just a couple of planes.
Bring in the big guy. This is our cold saw. It is basically a chop saw, but it runs 50 rpm at the blade. The blade is M25 steel, constantly quenched in a lubricating coolant. This little torque monster weighs in a bit under 200lbs and is the same size as a 10” mitre saw. The reason we took this route is the finished cut is clean, practically burr free, dead square and there are no sparks. Thats a big plus in a wood/metal set up.
We cut the blanks at a 45 degree bevel then send them off. By doing this, we ensure we are grinding up into a nice, tight, carbon matrix.
Here is where the magic happens. This is a quench and temper furnace, at Ky Heat Treating, in Winchester Ky. Fully automated, baskets of O1 steel get brought up to critical temperature, then quickly queched in warmed oil. They are then transfered to ovens where proper temperature is maintained to achieve the desired Rockwell hardness. We have ours hardened to Rc 60-61. This lprecision control of temperature and time ensure a consistent iron.
Back at the shop, its time to get sharp.
A horizontal edge sander, fitted with a 40 grit silicon carbide belt, produces a nice hollow grind. The grit on these belts is much harder than aluminum oxide and they handle steel wonderfully. The primary bevel is 25 degrees. I know it’s not spark free, but hollow grinding the blades on the wet stone was a time destroyer and we are, dare I say, trying to make a profit.
From here we move to a different machine, to get our secondary, 30 degree bevel. The constant water bath keeps the most susceptible part of the blade safe from the accidental “blueing”, that destroys the temper at the edge and produces much foul language. From here the blades get their backs flattened and cutting edges honed, via a combo of scary sharp and Japanese waterstone.
Side by side of 45 to 30 degree, double bevel, hollow grind.
Our blades next to other “standard” blade thicknesses. There is no chip breaker in a Nice Ash Plane. They were originally added to hand planes, to counteract the harmonic resonance of thin metal blades. With a 1/4” thick blade, chatter and harmonic resonance are virtually eliminated.
Thanks for reading.
-- It's only wood.