Thickness Planer Issues

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Forum topic by Rightousdan posted 06-01-2015 03:23 PM 834 views 0 times favorited 5 replies Add to Favorites Watch
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16 posts in 1130 days

06-01-2015 03:23 PM

Topic tags/keywords: craftsman 21758 planer thickness planer help powertools power tools tool question tip

Good Morning Everyone,
I am having an issue with my Thickness Planer (Craftsman 21758).

I have had it for just over a year and have been quite happy with the unit. It surfaces boards to a nice smooth surface and seems to have plenty of power.

I am using this unit specifically to bring down re-sawn walnut to 1/4 inch thickness.

I notices the other day that one of the pieces I ran through the planer seemed to be thicker on one end and thinner on the other. I measure the difference with my Digital Micrometer and sure enough it is out of square by about .2”

I am not sure how to bring the cutter head back to square or maybe its the blades that need to be squared up. The blades have been replaced many times over the years and it appears that the blades have little slots in them that match up with nubbins on the cutter head so that the blade is nice and aligned right off the bat.

Can anyone offer any suggestions on how I can resolve this annoying issue?


5 replies so far

View Dallas's profile


3599 posts in 2485 days

#1 posted 06-01-2015 04:22 PM

Are you saying that out of the 1/4” final thickness you end up with a board that is .05” tapering up to .25” from end to end? Or are you speaking about side to side?

In either case, it isn’t your blades that are the problem, it is more likely to be infeed/outfeed alignment.

-- Improvise.... Adapt...... Overcome!

View DrDirt's profile


4424 posts in 3740 days

#2 posted 06-01-2015 04:24 PM

really 0.2”? so nearly a quarter inch difference?

I am wondering if there is a way (if not adjusting the cutterhead alignment)... can the table be shimmed, getting some 0.002 brass shim stock and making washers for the “thick side”

Usually the slots in the blades allow you to offset the blade after getting a nick in it. If your surface has a little ridge along its length, usually it means the blade nicked something, so you can loosen the blade and scoot it over a millimeter or two, so that thenicks in each blade do not line up anymore.

-- “The two most important days in your life are the day you are born and the day you find out why.” Mark Twain

View TheFridge's profile


9460 posts in 1484 days

#3 posted 06-01-2015 04:30 PM

Sometimes the linkage to raise and lower the cutter head can loosen up.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View pintodeluxe's profile


5658 posts in 2811 days

#4 posted 06-01-2015 04:34 PM

Before you go tearing the planer apart, please clarify something for me.
Are you jointing this rough sawn lumber to S2S before planing the opposite face? If you are running rough lumber directly through the planer, it would be normal to have some variations in thickness.

Are the knives on your planer the indexing variety, or do they need to be set to appropriate depth?


-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Ripthorn's profile


1458 posts in 2983 days

#5 posted 06-01-2015 04:34 PM

You say micrometer and I think thousandths or tens of thousandths of an inch. If you instead meant .02, there are a couple of things to check. First is your stock. If you are sending a cupped board through with the crown down, the board will end up getting sent through crooked and one side will be thicker by some amount. Blade wear is possible, but not likely at that amount of difference. On some planers, the stock slides across a sheet metal surface. I have seen those get a slight bend which pushes one side up higher and therefore could make one side higher.

In short, if it is still running well, it is unlikely that the cutter head itself has gone a lot out of alignment, as any misalignment would be likely to cause binding in the bearing/bushing on the non-drive end of the shaft.

-- Brian T. - Exact science is not an exact science

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