Sunday, May 2, 2010

The Grimsdale Method, part 3

(Go back to part 2)

After posting this to the UK Workshop Hand Tools forum, there was some good discussion of stropping, split into several categories: strop on your palm,  strop on bare leather, and strop on leather charged with buffing compound. I've also seen people mention stropping on wood with compound.

The non-palm stroppers thought the palm-stroppers were crazy, while the latter said they'd done it for decades without injury. Once again we see the variety of methods and strongly held beliefs, all managing to get the job done.

Paul Chapman posted his setup, using leather glued to a piece of MDF with jeweler's rouge and a dab of Vaseline. This is similar to what Charles Hayward mentions in The Junior Woodworker (don't let the title fool you, though it was written for boys in the 50's, "junior" really means skill level, not age). After sharpening a plane iron, Hayward says the iron can be stropped on leather dressed with emery powder and oil. Bernard Jones' The Complete Woodworker, from the 20's, mentions using crocus powder and tallow.

(As an aside, Joel Moskowitz's footnotes in The Joiner and Cabinet Maker point out that sharpening is little covered by early woodworking texts, it was such an assumed skill, and this anonymous text from the mid-1800's is one of the few to describe it. Though there's no mention of stropping, it does mention that some shops would not allow a grindstone to be seen on the premises, controversy even then!)

Paul said he strops by pulling the blade held in a honing guide back across the leather bevel down several times. Then he removes it from the guide and repeats on the face, held down dead flat.

I gave this method a quick try free-hand using a scrap of leather and a stick of red rouge buffing compound I had lying around. I experimented a bit with pressure; too much pressure on the spongy surface is liable to dull the fine edge.

Light-to-moderate pressure produced excellent results. Where before the edges I had thought were sharp could take a few hairs off my arm or leg, the rouge-stropped edge took them all off in a clean sweep. Wow!


My initial test setup. The rouge stick was part of a Craftsman buffing pack.

I had seen green rouge (chromium oxide) over at Tools For Working Wood. Since I was ordering some other items, I added a stick. Ordered Wednesday night, it arrived Friday afternoon (it helps to live just a 6 hour drive from NYC!). A little research shows that where jewelers rouge (red rouge) is for precious metals like silver and gold, green rouge is for iron and steel.

While I was waiting, I reviewed Nick Engler's article "Very Scary Sharp" in Hand Tool Essentials. He recommends stropping with green rouge as the secret ingredient to any sharpening method. He does it free-hand. I also found Derek Cohen's excellent article Stropping with Green Rouge Versus Diamond Paste. He uses baby oil on the strop (the purpose of the lubricants is to keep the leather supple). It's worth reading.

I also found that "crappy" old oilstone I had tried before. Turns out it's a Norton 1B8 combination, coarse crystolon and fine India. Ummmm...why was Norton India bad before but good now? Can't blame the tool here, this was clearly a case of user error. It's instructive to see why I had poor results before. The coarse side was unused; the fine side had an ugly residue of old 3-in-1 oil. So it looks like I was using too fine a starting grit, and probably not using enough oil. I cleaned it up and used it for the remainder of this test. Worked just fine! Technique counts.


Norton 1B8 returned to use.

When the green rouge arrived I made up a strop block on rubber feet, using MDF and some old leather I had gotten for some Boy Scout project. A sharp crosscut saw works very well on MDF, and a stropped chisel makes a superb leather cutter. I glued the leather smooth side down with rubber cement (this is hard belt leather, so the rough flesh side is actually pretty smooth). The chisel I sharpened was another from my flea market collection with a chipped edge, so I started it on the coarse side of the combination stone, then the fine, then the Arkansas. Ready for stropping.


Carefully drawing the chisel back with bevel held at consistent angle for 5-10 strokes.


Drawing back on the face held dead flat.


Using the chisel as a paper cutter. Clean slicing!

I actually spent nearly an hour practicing with the strop and slicing up paper, it was so fascinating. I also used the strop on some chisels that were getting close to needing sharpening. It was able to bring them to paper-cutter in 30 seconds, as Derek had said.

At this point, I'm not able to tell if there's any difference between the red or the green. They both produced edges fine enough to slice paper edge-on and pare smooth end-grain shavings. Since green is intended for hard metals and red for soft, I'll go with the green. What is clear, though, is that careful stropping with one or the other is a worthwhile step.

As a novice woodworker, I can see the evolutionary steps in developing my sharpening skills, each one producing progressively sharper results in less time:
  • Chris Schwarz's article Sharpening Plane Irons (also in Hand Tool Essentials). This led me to order the DMT Duo-Sharp stones and a jig. As the first step, this allowed me to get my planes into a usable state. Reproducing the edge took a while though, mostly due to trying to get the jig back to the same angle. Deneb Puchalski's stone holder with built-in blade-setting stops helped.
  • Mike Dunbar's article Sensible Sharpening in the April, 2007 issue of Popular Woodworking. This got me away from the jig, shifting over to sandpaper on glass and side-to-side motion.
  • Jacob Butler's convex bevel. This took me back to the traditional stones.
  • Paul Chapman's rouge stropping.
The end result is this simple recipe:
  1. Pick starting stone based on condition of tool: coarse, medium, or fine India, or hard Arkansas. Do the next two steps for each stone in sequence, about 30 seconds each (coarse work on a damaged tool may take 5-10 minutes).
  2. Free-hand sharpen the bevel side using vigorous but controlled convex-bevel motion until a burr rises all the way across the edge.
  3. Sharpen the face side, running it up and down the side of the stone, keeping it dead flat. The burr will turn into a wire edge or flap and may come off at any point.
  4. Strop the bevel side, drawing back carefully, for 5-10 strokes on strop block with green rouge.
  5. Strop the face side, drawing back with it held dead flat, for 5-10 strokes.
For initial sharpening of a dull but undamaged blade, this takes about 5 minutes. For regular maintenance of a sharp blade, just 1 or 2 minutes. A heavily damaged blade may require 10-15 minutes of pre-work on 80-grit sandpaper on glass.

This method has its strong detractors. Everyone has their own preferences based on what they've been exposed to in their training and experience. If you're already satisfied with your sharpening method, there's no reason to change. There are plenty of ways to get the job done. But if like me, you're a novice searching for a fast, simple, effective method, this is worth considering.

Recommended Books
Hand Tool Essentials: Refine Your Power Tool Projects with Hand Tool Techniques (Popular Woodworking)

11 comments:

  1. No arguments at all with your, or most any other sharpening method. All of these methods work. I think most of the difference is how much time and money you want to put into them. I'm sure there's someone out there happy to provide us with the next great level of platinum clad sharpening stones. :)

    My reason for jumping in is stropping. Just last night I made my first strop. Like you, I'm not too far from Joel (actually about 1.5 hours), but that means being a long way from anyone who sells leather. I bought a shoulder split online from Tandy, who shipped it from the nearest store, Allentown, PA. Shoulder splits are thin, often used for glove making. The first two parts cut out of it went to the leg vise jaws. Incredible grip now. The next went to a strop, which I made from a 3/8 inch bit of ash. It ends up as a good hard surface, faced with a very thin leather, charged with Veritas green rouge. The leather is thin enough to hold the rouge well, and to avoid giving a blade enough softness to dub. I used normal sharpening pressure, no need to be light handed.

    What an edge! People talk about testing by shaving forearm hair. Yeah, that works, and most previous tests yielded a level of shaving that one feels, a bit of scraping along with the cutting. This level of sharpness causes the hair to fall off without the blade ever touching it!

    All in all, THANKS for the interesting adventure in sharpening.

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  2. Re: platinum clad sharpening stones: I'm waiting for the foamed steel matrix with microcrystallized carbon nanotubes formed by solar concentration furnace in a zero-G environment, since that ensures uniform distribution throughout the substrate, but the shipping costs from the Lagrange points will be astronomical :)

    I stocked up on several large pieces of leather several years ago from http://www.crazycrow.com/store/, along with a couple of throwing tomahawks (fun!). I think the piece I used was "blacksmith side".

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  3. I tend not to strop at all. Instead just a few quick but light hones and face flattenings across the stone - just little jabs 1/2 inch or so to finish off. As you would if the stone were all you had and you were in a hurry.
    Rouge etc looks like too much kit to me.
    Tempted to refer to Occam's Razor; "avoid unnecessary multiplication of entities".

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  5. And so the corollary to "pick starting stone based on condition of tool" would be "stop when a sufficient edge has been reached." It's easy to get carried away seeking the ultimate sharp edge! Then it's worth thinking about the durability and life of that edge. But it's good to know how to reach it when necessary.

    That's the next exercise, which can only come from experience, learning to balance the desire for sharpness with the practical limits of attaining and maintaining it. I can see where it could reach a point of diminishing returns, spending all your time keeping the edge as sharp as possible, when the work doesn't require it. I don't stop to sharpen my pencil after every sentence, yet the paragraph still gets written.

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  6. Why did you make your strop with the coarse side up instead of the smooth side? It seems to me that the tatty coarse side would increase and multiply jagged serrations, for lack of a better descriptor, whereas the smooth side would continue the progression from coarse to fine sharpening media. I'm not saying you're doing it wrong, I'm just wondering if the smooth side would be better? I seem to remember razor strops with the smooth side out and the coarse side to the blade, but that was thirty years ago . . . .

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  7. This is something I wondered about, too. Looking around, you see people mention using both smooth and suede (flesh) sides of leather.

    I have a small strop that I got from either Rockler or Woodcraft, that has suede on both sides. Tools For Working Wood sells a Horse Butt (really!) strop and mentions using it either side; Derek Cohen's article uses it on the suede side. SharpeningSupplies.com sells strop paddles with one side smooth and one side suede. And Paul Chapman's photo appears to use the suede side. So the evidence is...confusing! But at least using the suede side doesn't appear to be wrong.

    I may try a second strop done the other way. The leather I used is already smoother on it's suede side than the small strop I have. I'm also not even sure I have an objective way of telling the difference, the edge is so fine. Maybe one will require fewere strokes or allow heavier pressure.

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  8. What about a brown paper bag? I've heard that works, and it's certainly cheaper too.

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  10. hmmm? Thanks for the article. I just read all 3 pages. I understand about using the grits and strops. I'm a little confused about how to make the desired convex bevel.
    By the way, thanks to you I have my pine wall up for for the Wall-of-tools in the basement. Now on to organize them, then build my 1st workbench. (I'm thinking Morovian)

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    1. Hi John,

      For the most part, the convex bevel just happens as a natural consequence of moving back and forth on the stone. It's not so much trying to achieve a desired convex bevel, as it is just allowing it to happen.

      Typically people try very hard to maintain a desired flat angle through the whole stroke, resisting any change in the angle of the tool, but in this method you don't worry about that. As you push to the far end of the stroke, the tool has a natural tendency to dip just a bit. As you pull back to the near end, it has a tendency to rise just a bit.

      You can go with just that small amount of natural dip through the convexity, or you can make it more pronounced by deliberately dipping your hand toward the back of the stroke.

      As opposed to be very rigidly trying to hold to a specific angle throughout the stroke, this is much more organic. The actual cutting edge is the only spot where you work for a desired angle. The rest of it is just whatever convex shape you end up with.

      I'm glad to hear about your wall-of-tools, you'll enjoy that!

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