This question comes up fairly often and this is the how-to that works best. It works on the modern versions of blade-as-sole spokeshaves equally well. It’s not a difficult task but the tangs get in the way of conventional bevel-up sharpening, as you might with planes and chisels, so it’s is easiest to be done bevel up.
Making abrasive paddles
Typically sharpening work is the work of a narrow abrasive whetstone. Because the traditional spokeshave blade is not necessarily dead straight or flat but slightly curved along the length and slightly hollow on the flat underside face, a narrower stone works well. An inch or less works fine. Most likely you won’t have one and so it work well to use abrasive paper on a wooden paddle like the ones shown.
First you need to make the paddles, which are quickly made with strips of abrasive paper adhered to thin paddles of 6mm x 20mm x 175mm (1/4” by 3/4” by 7”) long scrap wood. I use double sided tape such as mounting tape to attach the abrasive and I do both sides of the paddle for economy. The yellow paddle is 120-grit. This is coarse enough for corrective work but for most work this may well be sufficient for establishing a cutting edge too. I keep one spokeshave with a blade with a coarser sharpening for the roughing out work. If you have only one spokeshave then you can simply hone to a more polished level as needed. You can use finer grits of paper to refine the bevel. In my case I used the EZE-Lap diamond hones in medium, fine and superfine grits. That’s somewhere around 400-1200.
To remove the cutting iron by tapping the tangs evenly alternating from one side to the other until it’s free.
How much the blade has already been sharpened affects the angle of presentation of the abrasive paddle to the blade. You must first establish the bevel angle for presenting the abrasive paddles to the steel and then grinding away is quick and simple. Place the blade on a support block as shown with the cutting edge aligned right on the corner edge of the block and then place the paddle of abrasive on the blade as shown and with the opposite end on the bench.
To determine the general angle of presentation move the paddle forwards or backwards against the cutting edge without abrading until the paddle hits both the back edge and the front edge of the blade simultaneously.
Now, by moving the paddle in short circular motions about 2 cm (3/4”) up or down and no more, with the opposite end of the paddle on the bench top, you can establish the correcting bevel to the steel.
Move across the bevel from one end of the cutting bevel to the other using these circular motions until the whole bevel is evenly abraded. This will establish a slight camber to the bevel and by carefully watching the bevel it should be nice and symmetrical too. Keep going until you feel a slight burr to the opposite, underside of the cutting iron, along the full length. Work as evenly as possible if the bevel is in good shape. If it’s way off, apply more strokes to even out discrepancy. Generally, even a bad iron takes only a few minutes to establish the bevel correction.
It’s worth mentioning here that so far the work done including making the paddles is not more than ten minutes.
Subsequent honing continues using finer grits of paper on paddles or the EZE-Lap diamond hone. Do both sides of the blade. On the underside keep the honing as flat as possible, spanning any hollow there is as shown below.
Further refining of the bevel can be done with a leather strip charged with buffing compound and hooked over the abrasive paddle like this. Or you can use a flat piece of wood instead. Just charge the surface of the wood with the buffing compound.
The opposite side of the blade, the flat face, often needs surfacing too. This usually means abrading through surface defections until the surface is clear of pitting and broken edges. Use the same sequence of paddles but not the leather strop.
This time use a piece of flat wood charged with buffing compound. Push the paddle flat across the blade in one direction only, otherwise the cutting edge will cut into the paddle.
Usually around 30 strokes works to polish out the blade. From here on it is unlikely you will need to do this again. It’s a one shot restoration process.
Tap the blade back into the spokeshave and start work.