Ron Hock's Sharpening Notes

        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.        
 Start by “grinding” the bevel until a burr forms on the back. It may not be very visible, and 
will get smaller as you move to finer abrasives, but the burr will catch your fingernail. If the edge 
radius is large (which is a fancy way of saying “if the edge is really dull”), it may take a while 
before the burr will appear but it must be there or you haven't done enough work.
It's the burr that tells us when the two planes have met (that zero radius thing,again.)      
 Now flip the blade over to do the back. Flattening the back is as important as honing the bevel. 
I repeat: Flattening the back is as important as honing the bevel. Think about it: in a bevel-down 
plane, like all bench planes, the back of the blade is the cutting edge. So you have to make the back
flat to insure that the edge is straight, smooth and sharp - without waves, valleys or “teeth.” 
Many woodworkers believe that the whole back, from the edge to the slot, should be flattened 
and honed. Others figure that a stripe about an eighth of an inch back from the edge is sufficient 
since the chip breaker rarely exposes even that much. Your choice.
 If you can leave the honing guide on the blade, just hang it over the edge of the stone or plate. If it's 
in the way, you'll have to measure and reset the blade extension from the guide each time you 
change grits. Start with the coarse abrasive you've been using and rub the back using even, firm, 
down-pressure and take even, steady strokes keeping the blade flat on the surface. Do this until 
your scratches are uniformly all over the area you want to hone. It's quite common for a plane
blade to have a slight “hollow” in the back and the early honing will reveal an arc of fresh metal 
along the edge and sides. You can expand this area as far as you want until the whole back 
is covered with the coarse scratches. When you're down far enough, and the planar surface 
of the back meets the planar surface of the bevel (zero-radius!) you will raise a burr on the 
bevel side. You're there.
        Change to a finer grit and repeat the above process. Once the back has been ground flat 
with the first grit, it gets much easier and goes much faster. It's a good idea to angle the blade 
slightly while working on the back and to change the angle with each successive grit. 
That way, you can readily see when you've honed off all the scratches left by the previous grit; 
another clue that it's time to change to a finer grit.         
Check the blade to be sure that it is staying square. If it's not, push a little harder on the 
high corner while honing the bevel to bring it back square. Proceed through the grits until 
you run out of them. After a few, the honed surfaces will begin to act as mirrors; a sure sign 
of imminent sharpness.        For most efforts, the 2000X paper is as fine as you need to go. 
But if you're doing the final planing on a surface that you don't want to degrade by sanding, 
you may want to go beyond the 2000X paper to a 6000X waterstone or a strop charged 
with chromium oxide compound (“green oxide” or “knifemaker's green”). 
The 6000X waterstone is a soft “stone” of cerium oxide that cuts fast but can be tricky to 
use because the blade wants to stick to the fine surface. Slow strokes, plenty of water and 
patience are required. The strop can be leather, cardboard, or wood; a flat, fine textured 
surface that will take the crayon-like super-fine abrasive is what you want. It's best to gently 
pull the blade across the strop or you risk cutting into it. Be careful to keep the back flat 
against the stone or strop and the bevel at the correct angle; you don't want to round off the edge.
        To test for sharpness, you can always shave the hairs on your arm (or wherever). 
A sharp edge will cut hairs with very little pressure. But if you're running low on hair 
(or just hate that patchy look) there are other ways. A sharp edge will catch on the flat 
of a fingernail or plastic pen barrel while a dull edge will skid  a bit. It's really that simple; 
try it a few times to feel it but it takes only the lightest touch and if it skids, it's dull.         
Also, you can see if a blade is sharp. Closely examine the edge with good light and if the 
edge reflects at all,  it's dull. (Remember that zero-radius stuff? It's the blade's edge radius 
that reflects light and if there is no radius -- The Goal -- there will be no reflection.)
        If you've just done a chisel, block-plane blade or other breakerless blade, you're done!
 But if you're working on a bench-plane iron, you're not done until you've polished the breaker. 
Make sure the breaker, when tightened in position on the blade, makes complete contact 
along its edge with no daylight showing; no gaps at all where a shaving could catch. 
Now polish the breaker ramp-surface. How much work is needed depends greatly on its 
condition, of course, and how smooth is enough is a matter of experience and performance. 
Use the same abrasives starting no coarser than you must. Breakers usually aren't hardened 
so the work should progress quickly. Rock and slide the breaker along the different grits 
until all coarse scratches are gone and the ramp area looks and feels smooth. Now you're done.
        Resharpen often and lightly, no coarser than necessary, to insure good cutting 
performance and save time in the long run. Good luck, have fun, and... “Ommmm”

Ron Hock
HOCK TOOLS
www.hocktools.com  ©2000