I re-sharpen disposable planer blades a few times, using a shop-made jig, before tossing the blades away. I use a set of three diamond hones to sharpen the blade at an angle 5° higher than the factory bevel to minimize the amount of metal I have to remove.
The jig is a single block that’s 1-1/2″ thick, 2-1/2″ wide and about 15″ long. My blades have a 45° bevel, so I cut a 50° bevel on one side of the block. I also cut a rabbet on the top of the block for the blade to nest in. The blade barely protrudes over the block’s bevel when it’s nested in the rabbet. I drilled some holes in the top of the block so I can secure the blade with screws when honing.
The lower end of the stone rests on the jig when I hone. This maintains the same angle with each stroke. Typically, I make five passes each with coarse, fine and extra-fine diamond hones. I count the number of strokes used on each edge so the knives end up the same width. After honing the bevels, I turn the blade over and remove the wire edges with the extra-fine hone.
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