My dad however, living in Northern Ontario, far away from a good sharpening service, has been resharpening his jointer and planer blades himself using a high speed grinder with a vertical axis, similar to the one shown at left, but bigger.
I found this grinder for cheap at a yard sale, so I decided that I should take another stab at resharpening jointer knives myself.
This time, with a fast running grinder, I had much better luck. The grinder is actually
a wet wheel, but it runs at 1700 rpm. The water pump on it is dead, so I always wet it
with my fingers. It's a very fine grit stone, so it's safe to touch while spinning.
Even with me grinding the blades at a slightly different angle, it still takes quite a bit of grinding to restore the edge. The best way I found to check if I'm 'done' is to see if any light is reflected off the top of the blades. The blade at left is a professionally sharpened with a good edge, while the blade at right is in need of sharpening. You can see light reflected off the edge on the blade at right, but none on the very pointy edge at left.
The blade shown here has nearly 0.1 mm deviation from straight, or about .004". It came with
my brother's used jointer. I did my best to resharpen it with my procedure for a test, but really,
these blades need professional resharpening. That said, when I put the blades back in,
they worked a lot better than before. But you could still see the effects of nicks in the
blades on the planed wood.
Here's what my resharpened blades look like. They are shiny, though not as consistently so. Note that I'm shining the light on them so that the normal bevel reflects back at the camera, as opposed to shining the light right onto the edge. So in this case, reflections are good.
Running a piece of hardwood over the knives straight resulted in a surface that was silky smooth to the touch. So really, this check of running soft wood over at an angle is more for obsessive perfectionists, as it is likely to make you feel dissatisfied with perfectly adequate blades. Although I suppose this tough test could be useful for comparing different sharpening techniques, or maybe even different jointers.
I was on more of a quest to get the blades exactly straight for my jointer some time later, so I used this method to get them really straight.
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