Changing planer knivesI had a rather unfortunate encounter between a fragment of screw in some reclaimed lumber and my thickness planer knives.
This one took quite a few scrapes to remove. Here's looking at the wood with the sun shining on it at a very low angle. This really brings out the texture, including a few other slight ridges from nicks in the blades.
You can see the nick towards the bottom left in this picture.
The knives are loosened by turning the screws in the wedges with a wrench. I turn them clockwise, which turns the screws into the wedges. This releases the pressure of the screw's head against the slot in the cutter head.
But other than this nasty nick, these blades are still ok, so I'm going to shift one to the left and one to the right so that the nicks no longer line up. This will, for the most part, hide the nicks.
A lot of small planers these days use thin disposable knives. for example, the Delta planer's cutter head uses double-edged disposable knives, although these can be resharpened.
Other small planers use knives with index pins, which are screwed more or less to the outside of the cutter head. These are very different from my planer, so this article won't help you much if you have that style.
I use compressed air to blow out the slot. Some of the crud that builds up on the wedges and the knives is best removed by scraping it off.
First I put the springs back in, then the wedges. I always end up turning all the screws in the wedges clockwise by one extra turn before reinstalling them. This gives me more room to work with. After that, I slide the knives in place.
Next I back out all the screws in the wedges until I feel resistance, then turn them back in (loosen them) slightly so that the knife can still slide up and down. It should be possible to push the knife down with a block of wood and have the springs push it back up a little bit.
Thickness planers with this style of cutter head come with a setting gauge for setting the knives precisely. This is the gauge for this planer. The ends of this gauge push against the cylindrical part of the cutter head, while the part right below where it says "1.5mm" pushes against the knife.
It's hard to take a photograph of this with the planer all together, but here's a photo I took of the cutter head for my homemade jointer as I was building it. The knife setting gauge that came with my delta planer is a different style. Note in the photo that I set the knives about a millimeter lower than that gauge would have set them to.
I start by moderately tightening the middle screw in the wedge, then I tighten all the screws that are not obstructed by the setting gauge. After that, I remove the setting gauge and moderately tighten the remaining screws.
These screws should not be tightened overly tight. As tight as you could turn with a screwdriver should be enough, certainly no tighter than you could tighten the wrench with just one extended finger.
But do as I say, not as I do!
Planer snipe on
small thickness planers
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