Thickness Planer Blades– Keep ‘em Sharp!
The thickness planer blades are relatively easy to change, so keep sharpening them for great surfaces.
If your woodwork is getting burn marks from the thickness planer blades, then it is time to change. Other indicators are the blades skipping over the piece, or ridges left behind on the surface of the wood (caused by knicks), or just overall decrease in cutting performance.
When it comes time to change your thickness planer knives, you may find that they can get pretty filthy depending on the type of wood you have been passing through the machine. When removing the blades, you usually find this accumulation of old sawdust happens at the connection of the blades to the cutter head and the head to the housing.
Before removing the blades please verify that the tool has been unplugged! Then follow the instructions that came with your machine.
After removing the blades per the manufacturers instruction manual, be sure to thoroughly clean all knife blades, the cutter head and any spacers, and any other parts that make up the cutter assembly that your machine may have. Mineral spirits is a good agent for cleaning these things up. This is an important step to allow you to set the blades accurately when you replace them.
After you sharpen the blades, or buy new ones, be sure to follow the manufacturer’s instructions as installing new blades or just flipping the dual-sided blades can have a different procedure for each brand of planer. However, there are a few general tips on installation that may help. First, consider putting a light coat of oil on all the parts to facilitate easy movement when making your fine tune adjustments. When you run your test board through the planner after installation, as long as you put on a light coat of oil, it will be removed in the first pass or two and wont damage future fine wood pieces. You may need to wipe down the bed after the test passes as the oil may spray onto it.
When you are replacing the blades into the cutter head, you might try to number the slots with a marker so it is easier to recall which blades have been tightened down. Take a look at each knife just prior to installation to verify its straightness and to see if there are any knicks. If there are nicks in the blade, be sure to offset them to the other blades so as to limit any ridges in the surface of the planed board.
There are a number of ways to check the alignment of the blades once you have installed them and gotten them close just by eye. Start by setting the blades just a hair above the feed bed to visually determine if the blades are parallel. When setting the blades, get as close as you can just by using eye judgment. Then tighten just so they are snug- not tight.
Now get a scrap board and put a mark on it level with the edge of the out-feed. Next, rotate the cutter head so that the blades catch the board and slide it forward. When the board stops- make another mark at the same edge of the out-feed table. Do this process for each blade and adjust the blades as necessary so that the two marks move the exact same amount for each blade. When they are all equal, tighten down the set screws and this is again for each blade just to be sure nothing moved when tightening the screws.
To sharpen, or not to sharpen?
The first question is really “If” you should sharpen. If your blades are dull, most are dual sided and you can just flip them around. If they are single sided, or you have already flipped them, then you must determine if you are going to just toss them and buy a new set, send them out for professional sharpening, or try to do it yourself.
If you have carbide blades, you really should probably send them out for sharpening. If they are High Speed Steel blades, then you can attempt to sharpen them yourself or send them out to a professional. I am sure you can find a professional in your area to sharpen the blades for you, however keep in mind that they tend to take off more steel than you might do at home and thus can shorten the lifespan of the blade. Of course if you are terrible at sharpening the reverse may be the case. In any case, I would take the blades to a professional for sharpening about every 6th time. They will grind out any nicks that might accumulate and put a nice clean square edge on them for you.
If you are unskilled at this, I would suggest new blades or sending the old ones out to a professional, but if you insist on sharpening yourself her are a few tips. You can buy or make a jig that holds the thickness planer blades while you use a conical sanding disk (don’t use a flat disk as it tends to uplift the blades and can be hazardous) to sharpen the blades, or you can purchase a slow speed sharpener that will do the job in a very short time. Most sharpeners can adjust for angle and depth and will evenly grind the entire blade with various interchangeable disks (course to fine). These can also be used for other tools like chisels.
Once you have sharpened your blades, don’t forget to de-burr them. If you leave the wire edge, excess material may knick the blade when you use it. Break down the edge with a slip stone then buff the blade across a piece of scrap wood making each pass on a new section of wood- again to avoid knicks.
Finally, if you use an oilstone hone from time to time, you will lengthen the life of your thickness planer blades. Good luck and be safe!
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