Why does my jointer cut tapers?

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Forum topic by mkrok posted 11-16-2010 02:26 AM 11157 views 0 times favorited 14 replies Add to Favorites Watch
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94 posts in 3197 days

11-16-2010 02:26 AM

Topic tags/keywords: question jointer

I was edge jointing a board the other night and noticed a difference in the “sound” while making the cut. The jointer usually makes a consistant cutting sound whne I finally joint the entire edge. That night I was nto hearing the cut as I got closer to the end of the board. I thne noticed that the jointer had cut a taper on the board.

So I tried another test. I ripped a board 5 inches wide on the table saw and edge jointed it on my jointer, About 10 passes just to be sure. I then measeured the width of the leading end 5 1/2 ” the trailing end was 5 1/8” Where in the world did I almost a 3/8” inch taper on it.

I checked the cutters with my jointer pal and they were all even with the outfeed table.

Any help will do. Thanks in advance.


-- Michael, South Florida,

14 replies so far

View Gary's profile


9377 posts in 3608 days

#1 posted 11-16-2010 02:30 AM

Michael, first thing I’d do is put a level on both tables, especially the outfeed side..

-- Gary, DeKalb Texas only 4 miles from the mill

View ajosephg's profile


1880 posts in 3737 days

#2 posted 11-16-2010 02:40 AM

Infeed and outfeed tables must be parallel.

-- Joe

View dbol's profile


136 posts in 3173 days

#3 posted 11-16-2010 02:49 AM

If you are not rotating your board that is why you are getting a taper. Even if your tables are coplaner and blades perfect you will always cut your boards with a taper. Unless your flip them after each pass with your last pass with the grain to minimize tearout.

View PurpLev's profile


8541 posts in 3824 days

#4 posted 11-16-2010 03:05 AM

why not?

FYI, a jointer will usually cut a taper. to make a board parallel there is a thickness planer.

that said – it may sound like your jointer is over tapering, or more than the usual. is it possible you have lowered your infeed table to take heavier cuts?

bottom line – If the jointer is producing a flat and straight edge/face than it is working just fine. thats what you want to check for.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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Scott Bryan

27250 posts in 3997 days

#5 posted 11-16-2010 03:07 AM

Michael, this is actually pretty normal. If you take enough passes a jointer will produce a taper. This blog was posted some time ago and dealt with this same subject. Tom Hintz gives a pretty good explanation for this phenomena.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

View mkrok's profile


94 posts in 3197 days

#6 posted 11-16-2010 03:10 AM

Wow, I never knew this. Poor technique sure as heck beats spending hours trying to fix something that is not broken. Thanks for all you help. Next time I will flip the board more often.

I am so glad I asked the question :-)

-- Michael, South Florida,

View SnowyRiver's profile


51457 posts in 3656 days

#7 posted 11-16-2010 03:15 AM

First of all, I would imagine that you measured the width of the board before you tried your test so you are sure the board was the same width at both ends before you started.

Check to be sure the tables are tight and not slipping down or dropping as you put pressure on the board.
Also do the same with the knives. Be sure they are tight and not slipping.

Secondly, the outfeed table will be higher than the infeed table by the depth of the cut that you are making. I have mine set for 1/32 inch cut for each pass so the outfeed table is 1/32 inch higher than the infeed table. As the board crosses over the cutter transfer your pressure to the outfeed table so the board doesnt rock as it passes the cutter.

dbol made a good point that after each pass, flip the board so the leading edge changes for the next pass. This will reduce an slight differences in the fence that you might have so you will end up with a good square edge.

-- Wayne - Plymouth MN

View juicegoose's profile


117 posts in 3238 days

#8 posted 11-16-2010 03:18 PM

I dealt with the same problem over the weekend. I was trying to joint a 6’ long popla board and kept getting a taper. One thing to remember is to look at your edges. If one is concave(center bows in) and the other side is convex(middle bows out) then you want o use the concave side, 2 points of register. This way you have more material on the planning surface. With that said Tom has some good advise on technique. I think for me it was that i was pressing down really hard on the outfeed side of the board. I probably should have just made sure the board stayed registered against the fence. To any extent I got so fustrated I ended up using a straightedge and circ saw and then ripped my pieces on the table saw.

View TopamaxSurvivor's profile


18380 posts in 3851 days

#9 posted 11-16-2010 06:55 PM

WoW, another problem solved that i didn’t even know was coming up ;-)) Thx LJ :-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View ChrisForthofer's profile


150 posts in 3243 days

#10 posted 11-16-2010 08:33 PM

After 10 passes I would expect some taper. Wood movement could account for some of it, possibly the infeed and out feed out of parallel, never hurts to check just to be sure. There are some good articles out there about squaring/truing up lumber, typically its, joint one face, joint the edge with the fresh face against a 90 degree fence, move to table saw, put fresh face on the table, fresh edge on the fence, rip to desired width +1/32, joint saw marks off of cut edge with a light (1/32”) pass. Then plane to thickness. Just using a jointer will never get you parallel edges. That being said if there is a lot of material to remove on the jointer it helps to flip the piece end to end between passes to stop any taper that might develop. Keep making chips.


-- -Director of slipshod craftsmanship and attention deficit woodworking

View TomHintz's profile


207 posts in 3574 days

#11 posted 11-16-2010 09:07 PM

A perfectly aligned jointer can cut tapers, mainly because it has no way to cut parallel opposing sides. That is the job of the planer. I get this very question very often and have a special story on this topic at the link below. Over the years I have talked with several jointer designers/manufacturers who all love this story and agree that we are just forgetting the purpose of the jointer.

-- Tom Hintz,

View Derek Lyons's profile

Derek Lyons

584 posts in 3744 days

#12 posted 11-16-2010 09:27 PM

Flipping the board helps – by the one overwhelming factor that can cause taper is poor technique. I.E. not applying proper pressure and by not properly shifting pressure as the board passes over the knives.

-- Derek, Bremerton WA --

View newwoodbutcher's profile


776 posts in 3026 days

#13 posted 11-17-2010 04:51 AM

Wow! Fliping the board. I didn’t know that. Thank you all

-- Ken

View Paul C.'s profile

Paul C.

154 posts in 3421 days

#14 posted 11-17-2010 09:07 AM

I would still check the cutter head with a straight edge. It sounds like it may be higher than the tables.

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