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Ron Hock's Sharpening Notes by Ron Hock

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Though many woodworkers find the sharpening process a pleasant pre-work meditation, most of us would just as soon get it out of the way and get busy woodworking. 

There is more to sharpening than I can cover here and I refer you to any of the many excellent books on the subject.  What I offer here, in extremely condensed form, are some ideas and methods to help make the task less forbidding.

First, The Goal: A sharp edge only exists where two planes (i.e., the back and the bevel of a plane iron or chisel, or the two bevels of a knife) meet with zero radius. Of course, “zero radius” is a theoretical ideal that eludes us as we move to the next, more powerful microscope.

There will always be some radius to an edge but The Goal is to minimize it. (Our fine-grained steel helps you here; the hardened particles in our steel are very small, allowing a smaller radius to be sharpened.)

Next, Getting There: Any of the popular abrasive devices can and will sharpen your blade.  The choice is yours. The venerable “Arkansas” oilstones are legendary and keep their shape and flatness with little maintenance.

These are a natural, quarried product that will last a lifetime. Man-made waterstones were more recently introduced from Japan, having a long history there as a natural stone. These stones sharpen more quickly because they are softer and thus wear faster, exposing fresh, sharp particles as they wear. However, their softness requires they be flattened often to avoid their tendency to “dish,” which makes accurate blade flattening and honing impossible.

Many woodworkers use a series of sheets of wet-or-dry sandpaper as their abrasive medium. A piece of glass serves as a flat base-plate and the sheets are simply switched as the blade is honed through successively finer grits. The low start-up expense, ease of use, and variety of grits (up to 2000-grit or finer from the auto supply) make this a great way to get started. Then there are diamond stones (great for coarser work), lapping plates (those who know them, swear by them), ceramic stones, leather strops (excellent for final finishing), and an overwhelming selection of powered machines all designed to make this task easier. Whew!

If you have a method that you like, that works for you, stick with it, use it. The following steps are mostly generic and you can follow along regardless of your abrasive proclivity. If you're new here and “grit-less”, head to the store that sells automotive paints and related supplies and buy a sheet or two each of 180-grit (180X), 320X, 400X, 600X, 1200X, and 2000X.

Some folks like to use 3-M #77 spray adhesive to stick down the sandpaper sheets; they sell it where you buy the sandpaper. Next, to the glass shop for a piece of 1/4” glass about a foot square. A marble floor tile, or scrap piece of monument or countertop granite, works well, too. Now go clear a spot on a workbench for the glass or tile.  With a new blade, start with the 600X paper. If the back needs a lot of flattening, don't be afraid to use a coarser grit to save time. When resharpening a blade, if the edge is chipped or horribly dull you may need to start coarser: 320X or 180X may be necessary.

Honing guides are useful things. If you have one, now is a good time to use it. Most block and bench plane blades are ground to 25° but some smart folks argue that there need only be clearance under the heel of the bevel. In other words, since the average bench plane blade is bedded at 45°, any bevel angle less than that will provide the needed clearance.

And a thicker bevel is stronger so the edge should last longer. Bench plane and block plane blades have traditionally been beveled to 25°. Our blades for the handmade wooden planes were specified by James Krenov to have a 30° bevel. Chisels get different bevel angles for different tasks: 25° or lower for paring, 30° or so for chopping. Experiment a bit with different angles to see which one works best for the wood and your style of work.

A honing guide helps with all this by establishing an angle and sticking to it. It can also shorten the whole process by letting you raise the blade a degree or two so that you're only honing the very edge. The angle of the bevel is determined by how far the blade sticks out of the honing guide.

At least one brand tells you right on it how far to extend the blade for a 25° or 30° angle. If your honing guide doesn't tell you how far to extend the blade, you'll have to experiment and measure to get what you want.

No honing guide? That's okay, but you'll have to exercise a bit more diligence and control while honing the bevel. It is important that the bevel be maintained throughout the sharpening process. If you rock the blade, the bevel will end up convex, “roundish,” and the actual angle at the sharp edge will be greater than you intended.

Not the end of the world, but it makes apples-to-apples comparisons between woods, steels, tools and bevel angles impossible. You can cut an angle template from a piece of cardboard, or whatever, and use that to check the angle as you go.


 
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