The method described below is not the best way to sharpen your planer blades. It’s much better to do it in a specialized shop, with the proper tools. But, if you find yourself with dull blades and a project that cannot be delayed (as it happened to me today, so I could shoot this short video), you can use this quick way to resharpen the blades. They will not be razor sharp, but you can keep working even on hardwoods with decent results.
I used a variable speed angle grinder, a velcro sanding pad and a few sanding discs. After the video you can find some tips that I think were worth writing down too.
- Keep in mind that you will, most probably, fail in your first attempt. So, it is advisable to learn to control the tools with some old blades, that are not useful anymore. It will take time and lots of practice until you will know how to hold and properly move the angle grinder.
- Do not use grinding or cutting discs. It’s pretty obvious that you will damage the knives for good. The only time I tried to use a grinding disc, I ended up with a pair of knives that couldn’t be used anymore, even after I took them to the local sharpening shop.
- Use good quality sanding discs. If the discs are bad, the heat generated by the friction will damage the steel so you will have to quench the blades again. I don’t remember ever hearing about someone that quenched planer blades successfully.
- If the planer knife has many knicks, don’t keep the angle grinder too much time in the same spot, as it may lead to overheat. Instead, use several passes on the entire blade. This way the blade will remain hard and straight.
- Regularly check the planer blade for overheating. If you cannot keep your finger on it without getting burned, the knife is too hot, so you need to stop and wait for it to cool down.
- As long as you make smooth passes, covering the entire length of the blade, there is no serious risk of distorting the blade. The only place prone to distortions is the beginning of the knife. If you are left handed, as me, that’s not too good, because that is the same part that is used for jointing boards. I found a workaround, by attaching a board to the fence of the planer, thus changing the part of the knife that cuts the board’s edge. If you are right handed, you most probably will start at the left and move towards right, so the area prone to distortions will be at the other end, so you won’t have any problems when jointing boards.
- The angle is important, but it is not essential. As long as you can maintain the angle in a 5 degree margin, there shouldn’t be any differences in the jointer’s performance. The usual angle that planer knives are sharpened is a compromise, anyway (ideally, you should have a set of knives for each species, since each type of wood is cut best with a slightly different angle).
- I don’t abuse this sharpening method, I only use it when I cannot go to the specialized shop to sharpen them, or when the knives cannot be sharpened using the tools they have (such as Metabo DH 330 blades, that are disposable ones, but I usually resharpen them once. In the sharpening shop, they cannot fit them in the machine, since they are too thin).