All Replies on How do i flatten a board that has a bowed edge?

Do you have a table saw? That would be the tool to straightline all your material before it goes to the jointer.

Technically what you’re talking about, I think, is hook In other words, if the board lays flat on the table but has an arc to it, like it wants to be the letter C, that’s hook.

If you need some help figuring out straightlining, I could help you.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

When passing the board over the jointer Ken, grip the board firmly with both hands and with the centre high part resting on the table with each end off the table, several shallow cuts will bring it so that the full length is flat on the table, or am I missing something?

-- Harry, Western Australia

I think what he is trying to do is put a flat edge on the board. The problem is that, with a cupped board, he is not going to be able to use the jointer fence to put a keen edge on it because of the bow. What is going to happen is he is going to end up with a beveled edge instead.

Ken, I would flatten the face first. You might want to rip the board into several pieces so that the majority of the cup will be gone before using the jointer, then, flatten, edge, and then edge glue them back into a wider board.

-- There is little that is simple when it comes to making a simple box.

Ken says that he is trying to flatten the NARROW edge. When Ken mentioned “through my old jointer” could he be refering to a thickness planer I wonder, if so and it is in fact a cupped board, then feeding it through the planer with the hump uppermost, a flat reference side will be produced. Your further thoughts please David.

-- Harry, Western Australia

Ken will have to produce more details, some of what I gathered that he was edge jointing first was from the sentence – “For what it’s worth i managed to get 24 out of 30 boards straight edged. These last few are kicking my butt.” So I took that as edge jointing. You are right, his other references also indicate he could be face planing.

The problem I see with using a thickness planer is that by the time the hump was gone, there would be nothing left of the board. I learned the hard way that too much stock gets lost when trying to joint or plane a cupped piece. When ran through the thickness planer, the feeder will press the board flat, will take off some material, and then the board will spring back to a cupped position after it completes the pass. It will pretty much take the same amount of material uniformly leaving you with a thinner, but still cupped piece. If the board is ripped where the board curves, in multiple sections, most of the cup will be gone, and less material will have to be taken off to make each piece flat.

-- There is little that is simple when it comes to making a simple box.

I was actually thinking of cupped across the board rather then length wise. I agree, that with the latter, it’s a case of feeding a banana into a thicknesser and you’ll get a thinner banana out! I’m sure that Ken will come back with a more detailed account of the problem, in the meantime we’ve discussed solutions to a number of problems which may help beginners reading this thread!

-- Harry, Western Australia

If a board has a crown (board on it’s edge sighting down the edge) and you want to save the lenght. Chalk line either edge use a skill saw and saw it stright. Then run it through a table saw to strighten the other edge. Presto changeo stright board!

-- What started as a hobbie is now a full time JOB!

Ken, when dealing with rough lumber I start by snapping a line on one edge with a chaul line (as lunn stated), or if the board is short enough, use a skill saw with a straight edge. That gets you a reference point. Then joint it (either power or plane) and you should be good to go from there.

-- There is nothing like the sound of a well tuned hand plane. - http://timetestedtools.wordpress.com (timetestedtools at hotmail dot c0m)

If there is one thing this thread proves, it’s that a picture is worth 1,000 words. Obviously, there are many ways to interpret Ken’s question.

I took it the same was as Lee, meaning that his best bet is to rip his board to relative straightness on the table saw before bringing it to the jointer. You can buy jigs for holding the board, or you can easily make your own.

-- Charlie M. "Woodworking - patience = firewood"

I assume by narrow edge you mean like the 1” edge of a 1×6.
So, like Lee said, the board wants to look like a C.
You can’t do anything with this on a jointer but make it worse.

You need to attach this board to a known straight board of equal or greater length, in such a way as the bowed, or hooked high part of the arc is overhanging the edge of the carrier board.

Now, with the straight carrier board against the fence of the table saw, and the fence to blade distance set to just let you rip off the high part of the crook.

After you have one edge straight line ripped, then you can remove from the carrier and put the new straight edge against the fence and rip the other edge to be parallel.

What you are left with is a narrower straight board.

-- Michael :-{| Diapers and politicians both need to be changed often; and for the same reason.

Hi guys, i added more info to the original postt

-- Ken, USAF MSgt, Ret.

I don’t have a picture of this, but I have also added a long piece of angle iron to my fence if I had a stack of lumber to rip. it cants the board slightly, but the jointing takes that out, and I have a true straight board.

-- There is nothing like the sound of a well tuned hand plane. - http://timetestedtools.wordpress.com (timetestedtools at hotmail dot c0m)

Ken, you are on the right track with the “sister board” idea. The general principal is that you must attach your hooked board to something with a straight edge that can run along the fence. Once you get the first edge straight, of course, you can just put that edge against the fence to straighten the other side.

These are pretty basic, but they do the job.

-- Charlie M. "Woodworking - patience = firewood"

I reckon that the straight edge and table saw is the best of the suggested methods. Rough sawn rules out double sided tape so probably a screw at each end is the answer.

-- Harry, Western Australia

Harry, Yea, I was thinking a screw as an option as well. Just didn’t want to add a hole in the boards. I am working with. I don’t have allot of room for to much waste.

-- Ken, USAF MSgt, Ret.

Ken, you could probably just use bar clamps, then double-stick tape some shims as needed to support the whole setup as you make the cut. That way there would be no screw holes, and you would not be relying on the tape to actually hold the board itself in place during the cut.

-- Charlie M. "Woodworking - patience = firewood"

Here is a straightliner that puts no metal parts on the saw table, does not involve dependence on tape and leaves no scars on the board. No chalk lines, no other power tools.

In image 1, from the left, a 6’ straightliner, a hooked board, and an 8’ straightliner.

The straightliner consists of a piece of plywood with a 3/4×1 1/4 piece of solid stock attached lengthwise on one edge and across the butt. (I have an additional one 10’ long. The paint makes it easy to find them in the rack.)

Image 2 shows the staightliner laid over the hooked board, concave side toward the fence. I measure the ends to see where to set the fence and cut the board. I remove the straightliner, measure the board’s breadth at the center, set the fence so what I cut off stays in one piece, and I have a board straightlined two sides.

On to the jointer.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

Ha! Charlie, I clicked on your link to the Rockler jig…. Then I realized I have that Jig still in it’s box in my garage. It’s been there ever since Christmas. My wife gave it to me and I really had no use for it that I could think of at the time. THen of course … I forgot I had the thing.

Lee, that’s my exact issue. and you are showing the solution I am considering since the length of my boards might not allow me to use the Jig Charlie suggested.

You guys are great!

Thanks!

-- Ken, USAF MSgt, Ret.

better late than never here guys

this is a modified from lee

two alternates or 5,0000 words

(exaggerated curve here for demo purposes only)

straight boards on right (you can have one handy from ply
or use one of your straight ones from the good pile you already have
curved board on the left
concave to guide pointy ends touching guide

push both thru saw together forwards and sideways to fence

alternate use a longer straight edge
(twice as long as work piece
and wide enough to stay straight)
and sticky down to table
or have a stop on side to hook saw fence
(to keep it from going thru too)
and again concave side of board to straight edge
push board thru

now do all boards one edge

then take off guide straight edge
and trim other edge of boards regular

i first saw this done when i was 23
and needed a straight 1×6x16
the saw guy at the lumber store
had one made from layers of ply
laminated to 16’ long
and just ran both boards freehand thru the table saw
together

keep things snug
and it works like a charm !

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle