Hand Tools

Subject:
A little more ...

Derek Cohen (in Perth, Australia)
There has been a great deal of interesting photography of buffed edges to date. I don't have the microscope to add to this, and so I will just take what has already been presented that provides evidence of enduring edges. Edges which last longer are lovely, but ...

... I want the edges also to be sharp and take the type of shavings that are evidence of a working tool, not just a long-lasting, but dull-ish edge. Rounded edges increase the cutting angles from 20/25 degrees to 40-ish degrees? I mean, chisels are not expected to act like BU planes, are they? Or the scraping chisel of Bill Carter?

Then I sharpened a chisel. Not just any chisel, but a Marples Boxwood with a 20 degree bevel. Actually, 5 of them. I wasn't in my right mind when I hollow ground them to 20 degrees - thinking that I could do with a few chisels with low cutting angles for dovetails - especially when they struggled to hold an edge at 25 degrees!

And the new buffed edge? Well, it took amazing shavings. Amazing! And it did not stop taking these amazing shavings .... which is a miracle, since the blades of these chisels are made of cheese.

They looked like this .. unfortunately not the Marples, but a Stanley #60 chisel (we all have a few of these for opening paint cans). The wood is Tasmanian Oak (similar to White Oak) ...

Sharpening system? Nothing much. I had a much used 6" stitched mop soaked in Lee Valley green compound. This was chucked into my lathe ...

The wheel was spun at 1450 rpm, which is the speed of a half-speed bench grinder in Australia. I use an 8" half speed bench grinder to hollow grind blades, so it made sense to use the same speed.

The bevel was presented to the spinning mop and angled about 10 degrees (please note, if you are reading about this method for the first time, that the mop is spinning away from the edge).

This resulted in a fine wire, and rather than buffing this off on the mop as David has done, I wiped the back of the blade on a section of hardwood with green compound.

Having satisfied my self several times over that this method worked, and that it looked a Good Thing, I decided to purchase another grinder rather rely on the lathe .

I got to thinking about trying this out on plane blades. In fact, I did so, and realised that it may not be a good idea. All the bench plane blades I have are cambered. Planing with a buffed cambered blade created shavings that were stringy, indicating an uneven edge. You can get away with this in a chisel, but not a plane blade. I shall try again, but that is my initial observation.

I also tried this with block plane blades. Now this was different: 25 degree straight bevel, just like a chisel. But would it cut differently, especially on end grain where low cutting angles are expected to rule?

A LN blade was hollow ground at 25 degrees, and then went through a typical process of extra fine diamond stone/Medium and Ultra Fine Spyderco ceramic stones, and a final polish on green compound-on-hard wood. At least the green compound would be the unifying medium.

The surface/shaving on Jacaranda (the softest wood to hand) looked like this ...

The buffed edge looked like this ...

The buffed edge felt sharper and left a cleaner surface.

This was repeated on Jarrah end grain. First the honed blade ...

.. and the buffed edge ...

Nothing in the two? If so, that is a win.

Regards from Perth

Derek

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