Sharpening plays into this discussion in a massive way, with the point being that sharp tools are no fix for incorrect technique. With that said, sharpening is the single most important skill in using tools, especially when using hand tools. If sharpening isn't understood, then woodworkers need to cease all activities and projects and immediately identify and separate all dull tools in their shop, and then learn what, when, and how to sharpen those tools. I cannot stress this enough!...stop everything right now and learn to sharpen all your tools! If you find you simply cannot sharpen a certain tool well... then as a last resort, you may have to resort to paying for a sharpening service. With few exceptions, I refuse to own tools I cannot sharpen. And if sharpening a particular item is a hassle, I may abandon that tool and find a better way of doing the task. This is in effect what I have done with a machine jointer and machine thickness planer. I figured out that by the time I spend fiddling with removing, sharpening and reinstalling those blades, I can have it done as quick and even better with simple hand planes. Does this mean I never use the machines? ...no but I sure use them a great deal less and could probably get rid of them altogether. I definitely would rather hand joint glued panels, and thickness planing is done for a modest fee at most suppliers of rough sawn timber provided there is sufficient amount involved. If quantities are low, then what's the big deal anyway? just do it by hand and get a better quality finish with less redundancy of work.
I used to say sharpening is an art, but I was wrong. It is a learned skill. There simply is no art to it, just the clarity of understanding of what sharp is and what will sufficiently achieve it. Mind you, I was criticizing some for being obsessive with sharpening, I am definitely obsessed with having every tool I have be razor sharp, including my household items as well. What I'm criticizing is not that obsession, but the obsession to have the latest innovation in equipment, the obsession to find some other way than the time proven and irrefutably effective methods, and often methods that are the simplest and cheapest. I don't want to jump ahead or get sidetracked on costly equipment, but I have to quickly say that I'm well aware that some things, while costly at the outset, end up being the cheapest overall. Diamond plates cost more than simple abrasive stones especially simple india stones. In the end, after very heavy use, they probably dollar out the cheapest over the life cycle of use. For avid woodworkers, small businesses, and other very heavy sharpeners, diamonds may in the end be the least money spent. This is especially true if they are the first and only item bought by the user and consistently used thereafter rather than changing methods. Are you starting out and have about 200 bucks? Then go with diamond plates and never look back. Use glass cleaner or a watery solution of Dawn dish soap as your lapping fluid and you'll do well. I do not advocate dry sharpening because in my experience it simply does not work as well. If you use any other system, dry sharpening is definitely out of the question.
So back to the subject of sharp. The question is and remains "what is sharp and how do I know I have achieved it (or how do I measure it)? I must give credit to Mr. Ron Hock for this quote that I personally like for its succinct and enlightening clarity: "sharp is the intersection of two planes with zero radius at the intersection". Picture any cutting edge where the edge is the intersection of two planes meeting with zero radius . The planes may actually start as curving (convex) surfaces, but where they intersect, they have as little radius as possible, or none at all. This very simply is sharp. Now begins the attending issues of how do I know I have that and how can I measure it? With these enter in the issue of the performance of the tool itself based on the quality and the integrity of its design. Also, other factors play into a tool's performance such as edge geometry, quality of steel, overall condition of the tool and possibly other important considerations, e.g. rockwell hardness, heat treatment and tempering, types of steels, types of material being worked on, etc, etc. We can discuss these briefly in overview, but it is probably beyond our scope here to cover all that in one posting. Indeed, it is the stuff of future postings to be concerned with the design and quality of a particular tool being written about. But back to the matter at hand, which is the essential characteristics of sharpness. Let's take for example the classic, basic stanley #4 plane. We can observe the design has long since been proven unparalleled. We know the thing can cut all kinds of woods and admirably (in the hands of a skilled operator) handle a variety of odd grain. We know it can handle endgrain with ease. With a cambered (curved) cutting iron, it can scrub off impressive amounts of wood. With a regular iron (well sharpened, and well set) the tool can cut shavings 1/1000th of an inch and leave a glassy smooth surface.
If your experience with a stanley #4 makes you doubt any of these statements, then I submit to you that your plane iron is not sharp. If you are positive it is sharp ( i.e. it is 25 degrees and easily shaves the hair on your arm? or slices newspaper effortlessly) then I submit to you the plane is not set correctly or is set way too deep. Flatness of the sole in my judgment should be the least of concerns, though you wouldn't know it from all that has been written and said obsessiing over flatness and squareness. By far, I have spent more time evaluating and tweaking the snugness and precision of the fit between the chip breaker and blade than I have spent on flattening and squaring the sole and sides. I have restored about dozen planes and it's possible I may change my stance on this after I tinker further on more planes (but I doubt it).
Now...for the basic steps of sharpening a blade such as a plane iron. I know I have spent considerable words to get to this point but I am sensitive to the fact that I or anyone should lay a solid foundation to any teaching they push on others. We have enough misinformation now, without me adding to the confusion. Here is my procedure....it's not new or innovative, just tried and true and very effective:
1. Remove the iron from the plane and the chip breaker from the iron.
2. If you think the primary bevel is at or near the 25degrees it should be, then practice placing the iron on the stone or plate and sensing the flat primary bevel in flat and solid contact with your sharpening stone. This is essential that you get the feel for doing this.
3. lay the blade on its back and rub the back flat againt the stone to test and evaluate the flatness of the back. I only involve 1 inch or less of the total area of the back from the edge upward. Some advocate tipping the blade with a shim such as a micro thin steel ruler or some such thin item to shim the iron off the surface and hence only rub the stone near the very tip of the blade near the edge. This creates a tiny back bevel. I don't advocate this but some swear by it. I don't like it because it changes the edge geometry and changes the cutting angle of the blade. A simple stanley/bailey plane was designed around a 25 degree "chisel grind" with no other angles involved. Why not stick with this? If you have more than one iron for a plane, you could try both ways and see which one you like.
4. commence sharpening after you flattened the back. (the back should never need flattened again but is worth checking now and then and touching up if necessary.) As you sharpen, feel for a tiny burr, or wire edge that forms when two surfaces intersect at a zero radius. You have two options before you proceed to the next finer grit you own. You can flip the blade on its back and drag the iron backwards and drag off the wire burr, or you can simply leave it and proceed to the next grit and sharpen it away. I drag it off, because I want to feel myself recreate the burr again on the next grit I use. There is a theory that when you drag it off, you create a jagged rough edge (at the microscopic level) that requires more work to smooth away.
5. Go through the grits you own, but don't feel like you have to sharpen to ridiculous fineness such as 15,000 etc. Paul Sellers has proven essentially that planes and chisels perform more than adequately at low grits of around 400. He said growing up and through his early apprenticeship they never sharpened with anything but a two grit india stone which is 250 on one side and 400 on the other( I have one and I know myself it is adequate). They probably stropped though but I'm not sure. I have an old india stone by Norton, and it works fine but it is not my preference. I actually like the cheap 4 sided diamond stone from harbor freight and really only use the 400 and 600 most of the time. I then use my old hard arkansas stone with oil to smooth things over and then I strop with green polishing compound on a piece of leather glued to a wood block.
I do have japanese waterstones in two grits, 800 and 3000, but seldom use them for plane irons and chisels. It hardly seems necessary since the stropping straight from an arkansas stone produces a mirror finish. The mirror finish is not required but you can feel less resistance to the tools as they cut when you have that polish on the edge. With chisels I often just strop them and that gets me back to work in seconds and then sharpen later on at some point when the stropping isn't producing the sharpness needed. Carvers strop alot and only sharpen when absolutely necessary. But they often aren't working in rock hard woods that dull tools as badly.
No comments:
Post a Comment