Powermatic Model 15 Planer Knive Question

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Forum topic by GAVol posted 03-23-2010 06:15 PM 4695 views 0 times favorited 3 replies Add to Favorites Watch
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11 posts in 2447 days

03-23-2010 06:15 PM

Topic tags/keywords: powermatic 15 planer knive adjustment knive marks

When I run a board through the planer, I get a fairly smooth board. However, if I run the board thru a second time without making any adjustments to the height, I get knive marks spaced about 1/8” apart all down the board. Questions:

1. Is this because one of the knives is set lower than the other two?
2. Why is the board smooth on the first run and only has knive marks on the second run?


This is my first planer. I’ve been restoring a Powermatic 15 Planer I bought used at an estate sale. It had sat unused and had quite a bit of rust. In the process I had to remove the knives. When I put the knives back in, I initially tried to use the PM Knive adjustment tool, but found the knive settings to be very inconsistent.

So, I used a pair of dial indicators to fine tune the knive settings. I numbered the knives (I, II and III). I zeroed out both dial indicators on the smooth part of the roller. I then set the knives to be .055 higher than the roller, which seemed to be the approximate height using the adjustment tool. There was no height specifications for the knives in the manual.

I thought I had gotten the knives set consistently, but apparently I did not. I also checked and adjusted the Infeed roller, chip breaker and outfeed roller to be .040 higher than the knives per the instruction manual.

Before I readjust, I need to know the probable source of the problem(s) and what I did wrong.

Any suggestions?

3 replies so far

View Mike Talbot's profile

Mike Talbot

22 posts in 2606 days

#1 posted 03-23-2010 06:33 PM

what you are seeing are not knife marks but dents from the infeed roller. the knives remove those marks when they remove wood.

View GAVol's profile


11 posts in 2447 days

#2 posted 03-23-2010 07:20 PM

Thanks!! Changing the setting on the infeed roller is MUCH simpler than adjusting the knives.

So is the infeed roller set too low or am I supposed to run the board through only once? Never used a planer before.

By the way, I have already watched Bob Vaughn’s videoes and that’s where I learned to use the dial indicator. I used his method to set the knives on my Delta DJ20 Planer. Since I had two dial indicators on magnetic bases, i was able to set one on each side of the PM15 and then adjust each side of the knives without having to move the indicators. I may make his jig the next time around.

I mess around with mechanical stuff and actully like learning how these machines work and in restoring them. So, I try to get the settings as accurate as possible, probably an overkill on my part.

View GAVol's profile


11 posts in 2447 days

#3 posted 03-23-2010 11:45 PM

rick3ddd asked “Why am I running the board thru twice”? Great questions. Never used a planer before. First time I ever used one was yesterday. You can make several passes on a Jointer. Thought it might be the same on a Planer. Newbie mistake.

It sounds like i have everything set right. I just need to learn how to properly use it.

Any tips on how to use a planer? All i know is what I read in the manual (which is not much) and what I have seen in some You Tube videoes (which assumes you know what you are doing). I’ve seen quite a bit about the techniques in using a jointer, but not much ion a planer. Example, how much wood should you be taking off in a run? Any articles or web sites you can point me to?

You guys have been very helpful.

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