Jointer making concave edges!

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Forum topic by Pezking7p posted 11-18-2013 03:56 PM 4467 views 0 times favorited 10 replies Add to Favorites Watch
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3217 posts in 1647 days

11-18-2013 03:56 PM

I’ve purchased an old grizzly 1182HW 6” jointer, but I’m having some real trouble setting it up.

After struggling really badly to face joint some boards last week, I did some research and went back after my jointer. I ended up having to shim the out feed table in order to get my 4’ level flat across both tables. I then set my blade height. I had pretty good success jointing the face of that board (3.5” x 60”).

However, now I’m trying to edge joint a board that is 10” x60” and the edge comes out concave every time! Because of the width of the board, I’m fairly certain I’m not applying too much pressure. I’ve tried re-coplanarizing my tables, adjusting out feed table height, I’ve tried to joint just the ends to get it close, but every time the edge comes out concave (except when my settings got way off and it didn’t cut at all).

I’m at a complete loss and I’m starting to suspect my level isn’t very flat (brand new, kobalt), but that seems crazy! If anyone can offer advice I would sincerely appreciate it. I’m on the verge of buying a new jointer, though I’m sure this won’t help me in the long run.

-- -Dan

10 replies so far

View jumbojack's profile


1676 posts in 2619 days

#1 posted 11-18-2013 04:04 PM

I used to have the same problem. I am not sure how I fixed it but here are some of the things I think I did. I was pretty sure I had my jointer set up correctly.
1 Light pressure, only enough to keep the material from chattering.
2 Get on the outfeed side of the material as soon as you can. MOST of the jointing is more ‘pulling the material through the jointer as opposed to pushing it through.
3 Listen and feel what the cutter head is doing to the material. This will dictate the feed speed.

-- Made in America, with American made tools....Shopsmith

View bowedcurly's profile


519 posts in 1724 days

#2 posted 11-18-2013 04:14 PM

I use 2 good framing squares to check my jointer you can use magnets or wood with slits and stand the squares up just check the top they will either be paralellied or have a gap you can get a good straightedge from peachtree in Georgia for around 60.00 that has a good base it’s phenolic and guarranteed straight

-- Staining killed the wood<<<<<>>>>>Dyeing gave it life

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Gene Howe

10479 posts in 3424 days

#3 posted 11-18-2013 04:18 PM

Ditto jumbojack’s suggestions.
Jumbo J. You use the SS jointer?

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View Loren's profile


10379 posts in 3643 days

#4 posted 11-18-2013 04:26 PM

I get the best results by assessing where the high spots are
and literally making targeted cuts by:

1. flipping the board and cutting from both ends to
get started. This works on shorter and less bowed
longer boards.

If the board is longer and more than a little bowed:

2. Making stepped cuts on the ends to remove bow. The
first cut must be shorter than either the infeed or
outfeed table. Once the first cut is made (say 15” long)
the board is lifted and there’s a step in it. Then
the edge of the step is used as a fulcrum. The leading
edge of the board is cut in the second cut and the
second cut continues for perhaps 30”. At this point
I’ve made an evenly tapered cut removing about 1/8”
at one end feathered down to nothing 30” back.

Repeat the process until the board face is flat enough
to run the other side through the planer. You’ll
throw away a lot of wood if you try to make every long
board dead flat. Flat enough to use is flat enough
as in a lot of woodworking board movement is constrained
by glue-up, grooves, or fasteners which serve to
pull bowed boards closer to flat.

View pintodeluxe's profile


5654 posts in 2808 days

#5 posted 11-18-2013 04:35 PM

You can check your level by flipping it over. If both sides of the level are flat to the jointer, there is a good bet it is coplanar. Use a feeler gauge when making these adjustments, as a difference of .005” can become a large error over multiple passes. I shoot for coplanar +/- .002”.

Also, make sure you are crowning the boards correctly. The concave side always goes down against the jointer table. If you place a board convex side down, it may never flatten out.

And then there are a few boards in every shop that are too warped to become furniture.

Good luck solving your dilemma.

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

View pintodeluxe's profile


5654 posts in 2808 days

#6 posted 11-18-2013 05:40 PM

My best guess is the outfeed table is too low.

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

View firefighterontheside's profile (online now)


18158 posts in 1852 days

#7 posted 11-18-2013 06:47 PM

Are all of your knives lined up parallel to and at the same level with the outfeed table. I bought the same jointer used a while back. The knives were not very well aligned. I use a straight edge that will stand up un its own and place ot on the outfeed and extended over the knives. With tool unplugged rotate knife head by hand. Set the knife height so that it just kisses the straight edge. It will drag my straight edge about a few millimeters. Make sure it does this on both ends of the knife the same and each kife the same as previous. When they are all aligned, reset the outfeed table to where the knives just touch the straight edge without moving it noticeably. You will get weird results if the outfeed is below the knives.

-- Bill M. "People change, walnut doesn't" by Gene.

View Pezking7p's profile


3217 posts in 1647 days

#8 posted 11-18-2013 10:25 PM

Thank you guys so much for the input. Loren, I think I’m going to have to remind myself that sometimes “good enough” is good enough!

I ended up shimming the outfeed table so that it raised the tail end higher, then I jointed the board and tested for flatness. I continued shimming the tail end up until my board was dead flat, which took about 3 iterations. I then re-tested the tables with my level and discovered that the level is flared on the ends.

I thought because I was buying a level that had a machined face it would be flat, but I was dead wrong. While this process has been really frustrating, I’ve learned a lot about my jointer, and hopefully I can start working on my technique (which I know is horrible). I learned a lot just reading the posts above.

-- -Dan

View jonah's profile


1696 posts in 3294 days

#9 posted 11-19-2013 01:29 AM

Some levels are actually quite flat, but as a rule they really aren’t best used as a reference surface unless you’ve checked them against a reliable straight edge. Mine is flat enough so I use it, but the one I had previously (same exact level) was like a banana by comparison.

There are plenty of options for getting an inexpensive but flat-enough straightedge. A lot of simple angle iron is really flat. So are the aluminum rules they sell at the big boxes for about ten bucks. Garrett Wade has a good one for about thirty, though their shipping is on the pricey side IMO.

View MedicKen's profile


1615 posts in 3457 days

#10 posted 11-19-2013 06:02 PM

Too much pressure as you are jointing the edges. ALL jointers will concave with too much pressure. lighten it up some and let the machine do the work

-- My job is to give my kids things to discuss with their

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