Jointer technique: need help?

[abram godshall]

Everytime I try to edge joint a board that is 3 1/2 feet or longer, I end up with a hump in the middle or the infeed end of the board becomes narrower than the middle and outfeed end of the board. I have 2 jointers and end up with the same result on both so it must be me. Any suggestions on what I'm doing wrong?

Thank you,
Abram Godshall

[Randy Klein]

You are applying more pressure at the ends than in the middle. Try to push the wood through instead of pushing it down. Let the weight of the wood keep itself down. If you must apply downward pressure, only apply it to those areas which are already flat and making contact with the jointer bed.

If you can't master that, then do what a lot of people do in the hand plane world, stopped shavings to produce a concave surface, followed by through shavings to flatten out the concavity.

1. Start your cut just inside the end by lowering it down on the spinning knives. Just be careful of where your fingers are.
2. Push the wood through until you almost reach the other end and lift the board up. Again, watch those fingers.
3. Repeat until it no longer actually cuts anything. Now you should have a concave shape where the ends touch and the middle doesn't.
4. Run the wood through from end to end, trying to maintain downward pressure on only those areas that are already flat (which will be the ends only initially).
5. Each additional pass will take more and more off the ends and you will approach the middle.
6. When you finally take a pass that has a continuous cut from end to end, stop and do no more. The board is now flat. One more pass and you may screw that up.

This may sound complicated but it isn't. Mark up the wood with a pencil and you'll see your progress a lot easier. Also depending on how much you're taking off , this may only require a few passes.

[Myk Rian]

Sounds like you may be putting pressure on the infeed side too long, before transferring pressure to the outfeed end.

[Michael McCoy]

You might want to check and make sure that your outfeed bed isn't set a little low.

[Andrew Nemeth]

Abram,

I'm goign to start with making sure the jointer is set up right, It's possible both jointers are not tuned properly. If you are certian they are set up right skip the next section and go onto the third.

First, make sure your jointer beds are completely parallel by raising the infeed table to the same height as the outfeed table and checking with a straightedge. Second, make sure your outfeed table is set dead even with the top of the cutterhead by laying the straigtedge on the outfeed table and rotating the cutterhead by hand (with it unplugged). I usually set the outfeed table a bit high to start with. Lay the straitedge across the outfeed table and extending over the cutterhead and rotate the cutterhead by hand watching the straigtedge for movement. If it does not move you know your outfeed table is level or higher than the cutter head. Lower the outfeed table and rotate the cutterhead again. Repeat this untill you see the straigtedge barely lift off the outfeed table. Now raise the table a hair and rotate the cutterhead, the straigtedge should not move.

Now for pushing a realativly straigt board through. Apply enough downward pressure to keep the board tight to the infeed table as you begin your feed. As the leading edge of the board crosses over the cutter head shift the majority of downward pressure from the infeed table to the newly jointed edge on the outfeed table. (Always be extremly careful of pressing directly towards the cutterhead, infact many people say never to do it under any circumstance. If something were to give, your fingers will go right towards the cutterhead. Unlike a tablesaw, there is no chance of reattaching anything that is lost with a jointer. I generally remove my left hand from the board as the leading egde is going over the cutter and place it back on the board as it leading edge is securly over the outfeed table.) Repeat this process untill the cutter makes contact over the full length of the board.

It is common to end up with a hump in the middle of a long board after jointing if there is a hump in the middle of the board before jointing becuase there is only one point of contact with the jointer bed and the tendency is to rock the board across the bed. On really long boads (boards longer then your jointer bed) this may happen even happen on the concave side of the board on occation. There are a couple of ways I use to remedy this depending on how long the board is and how much deflection there is over the length of the board.

For short boards, I just push it through making sure to transfer the downward pressure to the outfeed table as soon as it gets there (you must be VERY carful not to apply donward pressure to the board untill you get it securly onto the outfeed table. if you apply pressure too soon you can force the end of the board into the jointer head and it can catch creating a very dangerous situation as you are pushing your finger right towards the cutter). Likely, the board will only be contact the cutter for the first few inches before the cutterhead looses contact with the board. Repeat this process, each time the jointer knives should make contact with the board for a longer period of time. You know your done when the jointern knives are making contact with the board through it's entire length. (The board will likely be significantly narrower on leading edge than the trailing edge with this technique and this will only be amplified with longer boards)

For medium sized boards, I make an effort to hold the leading edge slightly above the cutter head as I am feeding the board in. Apply slight down pressure in the middle of the board as you are sliding the board forward. The cutter will initially not be contacting the edge, it will begin to contact the closer you get to the middle of the hump. As the middle of the board clears the cutterhead transfer the downward pressure to the outfeed side so that you are pressing the newly jointed surface to the outfeed table. Repeat the same technique untill the cutterhead is making contact from the leading egde through the trailing edge.

For really long boards, or boards that are really bent, I first make one straight rip on my table saw using a straigt line ripping jig. (If you have questions about this, just ask). Then I can join them on the jointer with standard techniqe.

I know I should not have to say this but please be very carful with the jointer. I do not want to give you any advice that may lead you to do something unfortunate. If you are not completly comfortable with any of the descriptions please ask for clarification. I should also tell you that the techniques I have mentioned were for the most part self taught. They have worked for me for many years but there may be better (possibly safer) techniques that are considered standard practice. I will be intreasted in reading what others have to say.

[Frank Drew]

It is common to end up with a hump in the middle of a long board after jointing if there is a hump in the middle of the board before jointing because there is only one point of contact with the jointer bed and the tendency is to rock the board across the bed.

Exactly right; for this reason it's often better to joint the concave edge, taking off progressively more from the high points (i.e. the ends) until you get a cut all along the edge.

If you decide to joint the convex edge, the one with the hump, or belly, in it (which you can see by sighting along the edge), your first cut or two probably won't touch the leading part of the edge because you're keeping infield table pressure on the hump until enough of it is taken out to provide a straight portion to the edge.

In other words, you have to take the hump out first on the convex edge, the ends first on the concave edge.

[Jerry Olexa]

A few years when I bought a new jointer, I had a few problems similiar to yours. What helped the most (after checking the alignment)was 1. Learn the technique of jointing ie. even, light pressure, etc and 2. Wax the jointer tables. After that, no problems....