Sharpening the Plane Blades

Guitar Making Hand Plane

The blade and breaker assembly sold here at J.S. Bogdanovich Guitars is of the highest quality. Once you receive them however, they are not ready to go. Some prep work is necessary to get them up to cutting the finest shaving. The surfaces of the blade and breaker that touch need to be flattened, the back of the blade needs to be polished, and the beveled edge of the blade needs a polished micro bevel so it will cut even the toughest wood easily.

The process for doing all this is easy to do, it will just take a little time. If done properly it will produce a fine cutting edge capable of smoothing and prepping a surface for a finish requiring very little sanding. Granted not all wood species are candidates for planing. Some have what is known as rowed grain where the grain direction of adjacent portions of a face of wood are in opposite directions which will likely cause tear out. Mahogany is one of these rowed woods but is the exception to the rule. Mahogany will plane nicely if your tool is sharp. It may tear out occasionally but for the most part it will plane well. Harder rowed woods like indian rosewood for instance may not be as friendly. These woods are best left to the scraper but may be thicknessed with a hand plane by planing across the grain at a 45 degree angle. This will not produce a smooth surface and will require some clean up with a scraper and sandpaper before it can be finished. If there is one rule it is the sharper your plane is the more likely you are to get good results. So learning how to sharpen properly is a must to doing good work.

Guitar Fret Leveling Kit

Flattening the Back Side of the Breaker

The back side of the breaker, the face that touches the back side of the blade, must be flat across its entire width at the edge where it touches the blade just behind the cutting edge. These two surfaces must meet cleanly all along their widths. Any gaps here will catch shavings as they are produced clogging the plane and making it very difficult to use.

Start by taking apart the assembly. Rub the back side of the breaker on a medium grit sharpening stone. Make sure the stone is flat. It is only necessary to get about an 1/8" or so of this face flat. There is no reason to flatten the entire face since it only touches the blade at the edge. The intent is not to sharpen the breaker but to flatten it, so a highly polished surface is unnecessary. What you are looking for is an even dull mark left by the stone all along its edge. You can place this edge on the back to the blade and look for gaps to check its flatness. The photo here shows a typically flat breaker.

Rosette Cutting Router Attachment

Sharpening the Blade

Once the breaker is flat, its time to turn your attention to the blade. The same thing must be done with the back side of the blade. Flatten it first on a medium grit sharpening stone until all the machining marks are removed and you are left with a dull even surface. Again, it is only necessary to do this to an 1/8" or so at the back edge of the blade. It is not necessary to flatten the entire surface. Once you have it flat it is time to remove the dullness and polish it up. Switching to a fine grit stone, continue to rub until you have a real shine all the way across and about 1/8" or so back from the edge. Without flattening the back of the blade you will not be able to produce a silky smooth perfectly flat surface with your hand plane.

Once the back of the blade is flat and polished its time to put a polished micro bevel on the beveled edge of the blade. The bevel that has been ground into the blade already is 30 degrees. The angle of the micro bevel you need to put on is not that important. Just realize the closer it is to 30 degrees the weaker the cutting edge will be and chances of it breaking off on a hard wood are pretty good. A 5 - 10 degree micro bevel is recommended to strengthen the edge and help it last longer.

For the straight blade just hold it steady and rub the edge first on a medium grit stone while keeping the angle as consistent as possible. Do this until you see a sliver of a shine out at the edge. Then switch to a fine grit stone and rub again at the same consistent angle until that tiny edge is polished as shown in the photo. This should not take that long since the edge is so small. Keep polishing the edge until you can feel a burr on the back side of this edge. That burr is the cutting edge bending over because it has gotten so thin. Once you feel this burr you are almost finished. All you need to do is rub the back side of the blade a few times on the fine grit stone to remove the burr and you are done. If you have done it right you should be able to produce the finest shaving with your plan.

The curved blade is sharpened the same exact way. The only difference is that you will need to rock it back and forth along its edge while you are rubbing it on the stone to get an even sharpening along the curve. Try to keep the angle consistent while you are rocking it. You may be surprised how easy it is to get a good cutting edge once you have done it a couple of times.

When your blades start to get dull return to the stone and repeat the sharpening process. After a number of sharpenings this micro bevel will begin to get larger. When it gets to the point where the micro bevel is no longer flat but slightly curved, it will be difficult to sharpen and it is time to redress the blade.

Guitar Tuning Machine Drilling Jig

Redressing the Blade

Once your micro bevel is no longer micro, or flat, you will need to grind a new 30 deg bevel and completely remove any evidence of the micro bevel. This is best done on a slow grinding wheel. I use a hand crank grinding wheel but an 1800 rpm electric grinding wheel pictured here, will work as well. The intent here is to not overheat the edge and temper it. If it turns blue you have made it too hot and will need to grind off all the blue before sharpening.

When grinding the straight blade make sure to keep the edge as close to perpendicular as possible. There is some room for adjustment of the blade from side to side in the plane, but there is a limit.

On the curved blade, shown in the photo, you need to pivot the blade as you grind, doing your best to replicate the curve and angle of the bevel. Once you have an even bevel at the desired radius, its time to start the sharpening process again.

Additional Plane Making Content

About Hand Planes | Sharpening Plane Blades | Hand Plane Adjustment Tips | Plane Making DVD | Plane Making Kits