Sunday, April 11, 2010

The Grimsdale Method

Over in the Woodwork UK and UK Workshop hand tool forums, there's a fellow who goes by the moniker Mr. Grimsdale. His real name is Jacob Butler, a joiner and furniture-maker in Derbyshire. His website is http://www.owdman.co.uk/.

Jacob promulgates a freehand sharpening method that is a bit controversial (if I may be permitted an understatement). He refers to it as the convex bevel.

To some, this is heresy; one should never round-over an edge! But this is a controlled rounding over from the top approaching the target edge angle, not a dubbing over. He argues that it's simpler and faster than trying to maintain a consistent flat bevel or use a jig. I'll let his description speak for itself here.

Sharpening is one of those things like dovetails where everybody seems to divide into armed camps and glare at each other menacingly. Put five woodworkers in a room together and they'll argue ten ways about the proper technique. So Jacob gets a lot of heat for this method. If you browse the forums, you'll see multiple references pro and con (and you'll feel the heat).

For those who like to put microbevels on their edges, this is like an infinite series of microbevels, where the lead microbevel is at the desired 30 degree angle. In mathematical terms, where two or more flat microbevels approximate a curve as step functions, this is the actual curve as a continuous function.

In addition to the basic method, he also came up with a simple jig for applying heavy pressure to the edge. Wait, a jig for jigless sharpening? Well, that's another heat source, so let's just move on.

I'm always happy to try something out if it looks like it'll improve my hand tool skills. Maybe I'll stick with it, maybe not. Part of the reason sharpening is such a touchy subject is that it's a critical skill that easily becomes an obsession unto itself. We really need something that's effective. So I gave it a try.

My initial attempt was on my sandpaper-on-glass setup, based on Mike Dunbar's Sensible Sharpening method: 3 grits of PSA sandpaper (80, 120, and 320), followed by 3 grits of automotive wet-dry sandpaper (600, 1000, and 1500). The results were excellent with an old Buck Brothers chisel and a plane iron.


The resultant chisel edge.


Cherry endgrain shavings. I was able to mark a line and shoot down to it freehand with this chisel, just as good as a shooting board.

Next I tried my DMT dual sharpening stones on a mixed set of beautiful old Stormont and Marples paring chisels I had gotten from Patrick Leach. Some of the chisels were very sharp, others fairly dull, and a couple seriously dubbed over.

I had stopped using the DMT stones because I had been using them with a jig and wanted to get away from dependence on it, and the sandpaper was faster for really heavy refurbishing (yes, I'm making the expensive rounds of sharpening systems). But the results were equally impressive using the DMT black, blue, red, and green sequence. For a couple of the chisels, I had to go back to the 80-grit sandpaper first; for some others, I just had to do DMT red and green. All of them were able to pare end-grain.

The last experiment was to use Jacob's jig on a chipped iron from an old Stanley #7 jointer. The jig allows you to apply a lot of down-force to the end of the iron. It supplies the leverage for a plane iron that the handle supplies on a chisel.


The plane is a bit rough but usable. No real rust, but the tote is broken off at the tip and the iron is a bit chipped, as is the cap iron.


Close-up of the iron showing the chipped edge that needs to be removed.


Mounted in the jig, bevel down. I put about 3 minutes of labor into the jig. First time using my North Bros. Yankee No. 41 push drill with the little shell bits, patent dates on it "JAN 25 98-OCT 29 01".


Working it vigorously up and down the length of the 80-grit paper until I had cleared the chipped end. This took about 5 minutes and raised a nice burr. The jig also helps protect your fingers; the metal gets hot!

The dip move that forms the convex bevel is pretty easy to master, and hardly requires conscious effort (which probably explains why so many people have trouble maintaining a flat bevel freehand, part of Jacob's basic premise).


The convex bevel after the 80-grit sandpaper. I added just the slightest camber, easy to vary the pressure with the jig.


After flipping the iron over in the jig, working the flat side-to-side for a minute or so until the burr is gone.

At this point the heavy work was done, so I removed the jig and switched to the DMT stones. I could have left the jig on to use with them, but I'm going for freehand here.


Flattening the chip-breaker edge.

The DMT stone holder is a variation of the one I saw Deneb Puchalski use at the Lie-Nielsen 25th-anniversary open-house. I've removed the jig-setting stops that I had originally built, and added a piece of leather as a strop in their place, per the recommendation at Tools For Working Wood/Museum of Woodworking Tools.


Full-speed convex-beveling up and down the length of the DMT black.


Up and down the edge of the stone to polish the flat.


Pulling a few quick strokes on the strop, alternating each side, after completing the DMT green.


The final edge after about 5 minutes total to go through the DMT sequence.

Now for the moment of truth: the proof is in the shavings. I have a scrap of quartersawn white oak from my current project that I've been using as a practice piece.


The jointer takes nice long smooth shavings, good enough for my work.


Close-up of the shavings.

It took less than 15 minutes total to get from chipped iron to smooth shavings.

My conclusion: this is a simple, fast, effective technique. Good enough that it's encouraged me to give old-fashioned India stones another try (since the old fellers didn't have these high-tech diamonds; would Roy allow DMT's in his classroom?). I've ordered a set of three Nortons, along with a quart of their honing oil. We'll see if I can achieve the same results with roughly the same level of effort using less expensive abrasives. Sandpaper sounds like a cheap system, but I find myself using it up faster than expected.

(Continue to part 2)

4 comments:

  1. Hi Steve, I've had a go at this method using japanese stones (Norton), I was surprised at the simplicity of the operation, it worked! of course I started with the B&Q chisels which immediately performed like stars! I bought a chipped small chisel for a pound last month, it turned out to be a dream, I really like this system, with practice I will get better, thank you for sharing such a gem!
    Yours, Knightlylad.

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  2. That's great! I saw your comment on the video. The method works with any sharpening medium, oilstones, waterstones, diamond stones/plates, sandpaper. About the only consideration is being careful with the waterstones, since you can score the surface easily.

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  3. Steve, It's almost 2 years since you posted this (the Grimsdale method). What is your preferred method for sharpening? Have you stayed with this method? I'm going to give it a try.
    Paul

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  4. Paul, at this point I use something of a hybrid approach. Partly it depends on the blade and what existing bevel it has, as well as the shape. I find that given the range of blade thickness, width, and length, it helps to vary the method. Sometimes I follow the double-bevel method, sometimes this one.

    Partly I'm just continuing to experiment with different motion patterns on the stones. I find that an hour or so fiddling with any method makes a big difference in control. That improved control even transfers to other methods.

    Mostly it's a matter of whatever seems most expedient at the moment for a particular blade. By now I've used this method on most of my chisels and most of my older planes. For my newer Lie-Nielsen planes and spokeshaves, with thicker blades and well-established bevels, I use the double-bevel, especially on the spokeshave iron. It's so small, I find it easier to sharpen side-to-side more than up and down the stone. I've been meaning to make a simpler holder for it for up and down sharpening.

    So the short answer is yes, I've stayed with this method, but I don't use it exclusively.

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