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I inherited a Foley Belsaw 985 thickness planer which I recently started using on a 120BF of 8/4 FAS Hard Maple and am having a problem with uneven wear in the knives. I've searched this forum and others for a similar issue but no luck finding anything.

I'm looking for recommendations on what could be causing the concave wear pattern and how to fix it.

SETUP
: When I finally set it up I cleaned the deck and rollers and waxed the deck. Then I cleaned the cutter head and installed a sharpened set of high-speed-steel knives that my grandfather in-law provided. He also had two other sets of worn-out knives in a box that can be resharpened.

USE: I flattened one side of all boards by hand. Each board was just under 1-7/8" thick and 60" long with widths ranging from 6-10". I started by taking 1/32" passes on the opposite face and worked my way down a few times until both were flat. I rotated back and forth feeding left and right sides on the deck. I get about 3" of minor snipe - but prepared for this in my measurements ahead of time so no worries.

OBSERVED WEAR: By the time I got to 1-23/32" I noticed that there was a hump on the planed face of the board - not a tiny thing like from a knick or anything but a pretty decent hump about 0.02-0.03" high. I checked the knives and sure enough there was a concave wear in each one with the deepest part about 1/3 from the left. I removed the knives from the head and the concave pattern was still there. I checked the two worn out sets of knives that I had and every single one had the same concave pattern.

OBVIOUS QUESTIONS:
  1. Was this caused by the sharpener and the concave pattern was there before I even started? I can't be 100% certain that it wasn't. I would like to think that I checked the sharpened knives for flatness before I installed them but I can also believe that it wouldn't have felt necessary. I'm just not positive on the answer to that one.
  2. Do the rollers look worn? Definitely yes. I'm certain that the rollers have never been replaced and there is a concave pattern in the rubber. They aren't damaged, however, other than the normal wear they look to be in decent shape. At one point the rollers weren't grabbing onto the wood too well; I tightened them a little - trying to make sure that I tightened evenly on both sides.
  3. Is the cutter head perfectly level to the deck? I honestly can't say. There's nothing obviously wrong. I haven't checked or made any adjustments to this and while I wait for the knives to be resharpened I'll be making a dial gauge jig and checking tihs. The machine is generally in fine shape and the deck height adjustment moves well without sticking.
  4. Are you using any dust collector? No. My dust collection system right now is only a shop vac and a cyclone - not enough to handle the amount of chips this thing is throwing out. I'm keeping the deck clean as I work in the open doorway of my garage.
Any thought or recommendations are appreciated. Thanks for reading.
 

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It's normal to have uneven wear on the knives because you tend to send the wood through the same spot every time therefore that spot gets more use. It's usually not enough to notice though. The humps indicate you surfaced wood with something foreign on it. Sometimes that can be a staple from a UPC tag and sometimes it's sand or some dirt embedded in the wood. This is more common if you are working with rough lumber. Nothing you could have done in setting up the planer could be responsible. A sharpening shop could have ground the knives uneven but unlikely. I would suggest the next time you have knives sharpened by someone you check them for straightness. .
 

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If all your knives have the same concave issue, I would suspect they were sharpened incorrectly. It's unlikely the previous owner and you both fed the work in the same manner sufficient to wear the knives AND they would be dull as well as concave only in the center. I have the same machine pretty much and there's no way that cutterhead would do that, it's too great a diameter. Nothing I can think of other than the sharpening process would create your issue. Get them sharpened by a different company than he used OR purchase a set of new ones from Holbren and start over. There are DIY method for sharpening knives that long if you want to try it yourself. Check out You Tube:

I only watched this one because it seemed to be the more accurate of those:

My knives measure 12 1/2" X 1/8" X 3/4" FYI.
 
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It can take a while to get to the bottom of a problem like this with a used machine you have no history with. I'd try running a board through skewed at an angle so that the whole width of the cutterhead is used. This is a quick check that the cutting thickness is uniform across the width of the machine.
A crowfoot gauge is the best way to check that the knives are seated uniformly in a cylindrical head. Unless the head itself is warped this is extremely accurate. Set the knives, check them, run some stock through and check them again. If there is a problem with the gibs, the knives may be pushed back into the head.
 

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Discussion Starter #5
For the benefit of anyone who finds this post in their search and wants to know the result, here's what I ended up with:

1) The knives were poorly sharpened, which is odd because they were sealed in wax so I figured it had been done by a pro. To fix this, I mailed my three sets to Highland's sharpening service in New Jersey and they came back in 10 days decently sharp.

2) After a good workout on some hard maple, I started to notice a very slight bow still present in my wide boards. I went back to measure the knives that I had installed and, sure enough, the center was about 0.025" deeper than the sides. I took them out and they were still flat to the straight edge. So I figured this wasn't the fault of the blade but the way it was being set in the drum. I fixed this by adding two layers of masking tape to the center of the knife where it seats to the drum on the bevel side. I re-installed and, voila - problem solved.

Thanks to all those who replied, thanks for the help.
 

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I often shim with masking tape, but I wonder how well it'll hold up with a planner knife, seems it could loosen.

Masking tape, USAS, universal self adhesive shim.
 
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