# Why does my jointer cut tapers?



## mkrok (Feb 16, 2010)

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


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## GaryC (Dec 31, 2008)

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


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## ajosephg (Aug 25, 2008)

Infeed and outfeed tables must be parallel.


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## dbol (Mar 11, 2010)

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.


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## PurpLev (May 30, 2008)

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.


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## sbryan55 (Dec 8, 2007)

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.


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## mkrok (Feb 16, 2010)

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


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## SnowyRiver (Nov 14, 2008)

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.


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## juicegoose (Jan 6, 2010)

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.


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## TopamaxSurvivor (May 2, 2008)

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


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## ChrisForthofer (Jan 1, 2010)

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.

Chris.


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## TomHintz (Feb 4, 2009)

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.
http://www.newwoodworker.com/jntrtaprs.html


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## DerekL (Aug 18, 2008)

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.


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## newwoodbutcher (Aug 6, 2010)

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


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## pcott (Jul 7, 2009)

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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