Jointing woes

[woodynoob]

The jointer I used to create my poplar wedge has a 12 inch blade and the tables are just under 4 feet each.

I didn't have much time, but did take a warped piece of pine and jointed and surface planed it down--no problem. After reading the advice in this forum, I had a better feel for the wood.

[Carpenter96]

I don't know if I have been doing this wrong. I was taught to have all pressure on the infeed side at the begining and even pessure on infeed and outfeed tables once the board is on both tables and to finish with all the pressure on the outfeed table. I have taught many students this method and they learn very quickly that uneven pressure will result in a wedge shape. Just a note that cup is across the grain from edge to edge of the board and bow is along the grain from end to end. No disrespect to your instructors but if the machinery is adjusted properly they should be able to tell you what is wrong with your technique. With the correct technique and some practice it should not take long until you are jointing with the best. Also plus one on the Jointer is to make one good face and one edge that is straight and 90 degrees to the good face. It was never intended to dress all four sides of the lumber. The thickness planer makes parallel faces and the table saw makes parallel edges.

Regards Bob

[Lonnie in Orlando]

I attached this chart to my jointer to help me diagnose problems ...
> R&F Woodworking

- Lonnie

[capncarl]

A jointer is like a blender, a couple of passes through is almost too much, each additional passes through makes results worse.

capncarl

[LCHIEN]

...

You said even the smaller jointer in the shop is bigger than the ones you have seen in retail stores. How big are they? Normal for most home shops is a 6" jointer. An 8" jointer is a luxury in most cases or, like me, a deal just came along that was too hard to pass up.

There's two main things that define a jointer... one is the width that you can joint and as Pappy said, ones for hobby use are most often 6-1/8" and sometimes 8", but there is also the length of the infeed and outfeed tables, generally for 6" jointers they total 44" and the general guidelines are that you can properly joint boards twice the total length.

Other key stats are number of knives and the HP of the motor.

So aI am curious, too, how large is the jointer in your shop class?

[Pappy]

Take heart in the fact that you are not the first to have problems in learning to use a jointer. A jointer is one of the simplest of all stationary power tools, but probably the most difficult to master. Practice is the key. Once you hit the right combination of speed, pressure, and hand placement you will wonder why it took so long to figure it out.

The link in Ken's post is one of the best tutorials on jointers I have seen. Since you don't own the machine, make sure the owner agrees that adjustments need to be made before making them. As to technique, read the article and watch the video several times. As has been said, the pressure should be applied to the outfeed table once the stock has passed over the knives. I will add that the pressure is applied just past the cutter head, using a hand over hand action as shown in the video. .

You said even the smaller jointer in the shop is bigger than the ones you have seen in retail stores. How big are they? Normal for most home shops is a 6" jointer. An 8" jointer is a luxury in most cases or, like me, a deal just came along that was too hard to pass up.

[Ken Massingale]

Opps! Moderated a reply. Sorry, Ken.

Good advice, Ken. That is the way I learned it as well.

What did you do to me you darn Mod????!!!

I missed your slap completely Lee.

[Stytooner]

Opps! Moderated a reply. Sorry, Ken.

Good advice, Ken. That is the way I learned it as well.

[Ken Massingale]

"Daryl—When you say that the pressure should be applied on the out-feed table, this is not what I’m doing. For this piece of wood, I’m placing firm pressure toward the rear of the wood (is that the “in-feed table”?) and light pressure on the “out-feed table”. That was what I was told to do…"

That is your problem. You can't do anything but make a wedge with this technique.
If the instructor taught this you really need to consider what else he may be teaching incorrectly.

Closely read Tom's instructions and explanations here and watch the short video at the bottom of the page.

[All Thumbs]

One more important thing to remember is that, it is often better to rough cut a board before jointing it. If you have a 1/2" bow over the length of an 8' board, but only need three boards approx. 2' long, then by cutting that 8' board into thirds before jointing it, you have substantially reduced the cup in each of your shorter boards and therefor will need fewer passes over the jointer and through the planer.

[woodynoob]

I'll take some time in next week's class to examine the jointer and get a better understanding of how it works and it's measurements. I'll try some tests to see if the components are aligned, assuming the teachers don't intercept me.

The jointer I was working with is big.. Not a home shop jointer by any means. There is a "small" jointer available also, but that is still much bigger than any jointer I've seen at at retail stores. So, the wood I'm working with is shorter than each table--no problem.

Excellent idea about the winding sticks. I had read about them before and thought they were primarily for hand tool (non-powered) woodworking, but I can see how useful it would be to understand the wood I have in hand.

[Brian G]

I think this is being overthought. All you want is a flat face on one side. When you achieve that, stop face jointing. Use a straight edge across the face to figure out if the face is flat.

If your board has substantial bow, you're not likely going to out-joint and out-plane with power tools nature's desire to make your board do what it wants to do on its own. You can probably defeat nature with hand planes, though.

Practicing with rough boards is a good idea. Use a pencil and draw cross-hatches across the entire length. This will give you an idea of flaws in technique or problems (cup, bow, twist) with your stock.

I don't bother with edge jointing until after I thickness plane. This lets me "correct" grain alignment by bandsawing my own reasonably straight edge, joint it straight and square to a face, and then rip to dimension. You don't have to accept the sawyers idea of what the straight edge should be.

[leehljp]

I might not understand completely how a jointer works in terms of the geometry of the wood, the infeed and outfeed tables and the cutter itself...

I personally think that this is the crux of your problem, and to me, there is one step missing for your situation. Look up "winding sticks," and give that a try. Repeating what I said in my first post, to me, you probably have boards that are twisted or bowed just enough to cause the problem without it being seen by the naked eye before it begins.

Winding sticks will show the minute' twist, or bow that the naked eye misses. With the winding sticks, you can see before hand what area and approximately how much is going to get planed on the jointer before it gets level on a specific side.


To be honest, even a thickness planer will not get some warps out, but will generally leave the board with even thickness.

[mpc]

Also, how long is the workpiece relative to the jointer table lengths? If the workpiece is too long for the jointer it'll be almost impossible to get a consistently flat/straight surface. About twice as long as the total jointer table length is the typically recommended limit. For a beginner, I'd first practice on pieces that are shorter than the total jointer length.

My understanding (I don't do a lot with jointers; the one I have is a small benchtop model and I rarely dig it out) is:
a: do not apply a lot of force to the workpiece. If the piece is bowed in cross section, or twisted along its length, applying a lot of force will just squash it into a flatter shape so the blades end up removing material from the whole width of the board... then when the force is released the board flexes back to its natural shape and the original bow/twist is restored. With low downward pressure the blades only cut the high spots. The pressure used should be enough to keep the board in contact with the tables, especially the outfeed table.

b: the blades must match the outfeed table. Quick/easy test: get a flat board about a foot long or a little longer. Set it on the outfeed table with one end hanging over the blades. With the jointer unplugged, rotate the blade head by hand. The blades should just nick/scrape along the board. If they dig in or try to take a bite, they're too high relative to the outfeed table and the jointer won't work correctly. You can use a metal ruler, blade from a square, etc. to do this test as well. You'll have to test at several positions across the blades though: blade end nearest the fence, mid-way away from the fence, and at the far end of blades. The "ting" you hear when the blades hit the rule should be consistent at all 3 positions; if not the blades are mounted cockeyed, cutting deeper on one end compared to the other end. Or they're worn and don't have a straight cutting edge. (edit: what rcplaneguy posted while I was busy typing)

c: boards with a lot of twist, or twist+cup, are hard to joint because it's difficult to keep the board at a constant attitude as it moves across the blades. Especially if the board is longer than the infeed table; then the "high spot" may start off the infeed table and will thus lift that edge of the board during cutting when the high spot finally reaches the infeed table.

mpc

[rcplaneguy]

A tapered cut is usually a sign that the jointer knives are set too low. If you place a board on the outfeed table and rotate the cutterhead by hand, each knife should catch the board and drag it 1/8". If this is not the case, readjust your knives until the board is moving 1/8" for each knife -- test at each end and the center. If it still cuts a taper, adjust the knives so the board drags 1/32" to 1/16" more (5/32" to 3/16", total). If the jointer suddenly begins to make a concave cut, the knives are too high and you need to back them off so the board is dragged 1/32" less.