How to prevent bowing when preparing a board?

[Aaron Stiff]

VERY new to woodworking, so this probably sounds like a silly question, but I’m just wondering what technique I should be using to eliminate creating a bow in the board I’m preparing. I can understand using winding sticks to remove twist, and sighting down the face will expose cupping (depression across the width), but how to I detect and prevent bowing (depression across the length)? Do I sight down the face edge? And is it just something you have to feel for when planing? Thanks!

[Stijn Bossuyt]

Hi Aaron,
to check for bow, you usually use a straightedge. I use an aluminum L-profile, but you could also use a long enough level or make a straightedge from wood:

Making a Straightedge

If the wood is very thin (let’s say 1/2 inch or less), don’t stress too much over a slight bow. The construction will keep that board constrained.

[Aaron Stiff]

Thanks! I’ll check that video out.

[Benoît Van Noten]

To flatten my bench-top, I used the edge of an inexpensive 1m aluminium rule. Although a longer one might have been better. When placed on the board, it should drag all along its edge everywhere.
Placed on a high spot it will “helicopter” – take thin shavings locally to remove the high spot.
If there is a hollow, the rule will not drag in the center – remove material at one or the two extremities.
I also check diagonally.
When doing it for the first time, one might have the impression to chase one’s tail 😉
I can not trust my eyesight because of my progressive lenses.

[Aaron Stiff]

Yes! That’s how I feel! One minute I’m too high, another I’m too low. But this is literally my first time planing an entire board, so I keep trying not to beat myself up. 🙂

Thanks for the advice. I’ve kind of discovered those things you were talking about, like helicoptering. I’m glad I left 1/8″ on each side. 🙂

[deanbecker]

Mark the four edges first.
Plane down to the mark all the way around. This leaves a hump in the middle
Then plane down to the mark going slow so as not to over shoot. Mark the surface with pencil lines and stop when they dissapear and remark.
Set the plane shallow at first til you see how much you remove.
Until i set it find i overshot a lot dont spare the pencil lead. Its your friend

[Aaron Stiff]

Great advice. Thanks!

[Colin Scowen]

Another good video to watch is the ‘Making a door’ video. It’s a free one. I watch it on spewtoob, but it may also be available on this site.

Colin, Czech Rep.

[Aaron Stiff]

Great. Thanks!

[Benoît Van Noten]

Making the edges first.
I have not tried it, but there is a description of the process in the book from André Roubo.
Starting from a rough sawn board, one makes two straight and coplanar (no wind) rebates first.
It is partly shown in this video:

look from about 11′.
If the rebates are not straight, the board will not be flat.

[Aaron Stiff]

Thanks! I’ve seen a few of Rex Krueger’s videos, and they’re very interesting.

[Roberto Fischer]

I wonder why we usually don’t see these winding sticks more. They do appear like too much fluff and no net benefit over the simpler ones. I can’t say that I’ve tried them though.

[Benoît Van Noten]

With simple winding sticks, one has to flatten the two ends of the board first; otherwise the winding sticks might rock and give unreliable information.
I always flatten a few inches at the end of the board to avoid this.

Those removable feet might be handy to choose between various rough sawn boards without having to plane the ends first.
Taking them with you to the lumberyard?
Those removable feet don’t seem difficult to make for one’s existing winding sticks.

[Author]

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