Best way to cut a thin board that resists warping

I want to cut some boards to be used as the covers for a book. The boards would typically be about an eighth of an inch thick and book size in dimensions (the average book is 9" x 6"). What would be the best way to cut the boards to minimize the chance of warping? Since book covers are not attached to anything, there is nothing to resist the board from warping, so a cut is needed that will cut to an absolute minimum the chance of warping.

As I see it, there are two basic possible approaches. One is to cut the board radially through the log (shown as A in the figure below). The other is to cut the log like a salami, and then cut the rectangle of the board out of the salami slices (shown as B in the figure below).

Method A has the advantage that a smaller log could be used. For example, a 9x6 cover would require a timber of 6" diameter using the cut in A, but in B, the diameter has to be the length of the diagonal, or about 11" in the case of a 9x6 cover, which is almost double A. However, on the plus side, a single tree will provide a lot of salami slices, but only a small number of radial cuts.

Now, as I understand it, a tree absorbs water longitudinally, so in the case of A, moisture would be absorbed at the top and bottom of the board, so this could lead to the top and the bottom swelling more than the middle. However, in B, the moisture would be absorbed equally across the face of the board. So, based on this idea my expectation is that B would be less susceptible to warpage, but I am asking here to verify this idea.

• Between these two A most definitely! If you need close to the full width of the log cut out the heart and then glue the two pieces back together. This is after seasoning obviously so you won't have usable wood until after about 6-12 months unless you go with plywood. B is just not viable no matter where it was taken from a slice, a big piece of end grain like this (even in a very strong wood) you could snap apart with little effort using just your fingers. – Graphus Jun 7 '18 at 15:25
• Actually, neither. Ideal would be to use a log of more than double the smallest dimension (say, 15") and cut 6" slices radially, leaving out the log's heart. This is called "riven" lumber, and it very wasteful and expensive. Settling for quarter-sawn is probably a reasonable compromise. – Lee Daniel Crocker Jul 3 '18 at 18:53

Are you familiar with how the wood fibers are aligned in a tree? They (mostly) run from top to bottom and are bonded together with lignin. If you used the 'B' method the wood fibers would be running into and out of the page when viewing your diagram. This would make the bond between neighbouring fibers short and weak - the cover would snap easily. This is why wood is very rarely cut this way.

For stability you want quarter sawn wood. This is because wood expands twice as much in the direction along the growth rings than in the direction across the growth rings. This makes flat/plain sawn boards warp.

As shown in the picture, ideally you would take a larger log and make a whole bunch of covers from it.

If you are limited in the size of log you have then method 'A' might work; but I believe the center of the tree may cause issues, in some species at least. Don't quote me on that though.

Another option would be veneering over thin plywood.

• @Treow Important to note in Jambo's image that no boards in the quarter-sawn method include the very middle (pith) of the log. This part of the log is weak and problematic for a variety of reasons. If you need a wider piece you can glue-up two quarter-sawn pieces edge-to-edge without loss of strength and if done correctly, even enhanced visual appearance. – scanny Jun 7 '18 at 4:25
• If you even try to use the pith in something this thin you will find out very quickly that you should have followed the advice of @scanny – aaron Jun 7 '18 at 12:17

A, an extreme example of quartersawing, is the way to go. B will not so much warp as check catastrophically.

• A is not quartersawn, it is plain sawn. – SaSSafraS1232 Jun 7 '18 at 16:51
• How would it be different if it were? (Hint - in this particular case, for this particular piece, there is no difference.) – WhatRoughBeast Jun 7 '18 at 19:38
• A quartersawn board will NEVER go all the way through a log. The first step is literally quartering the log, that's where it gets the name from. The whole point of quarter sawing is to get the most stable board possible, so you don't want the pith in it. (Hint - This makes a huge difference.) Scroll up and look at the diagrams Jambo posted and think about which one Treow's "A" scenario matches up with. – SaSSafraS1232 Jun 8 '18 at 0:07
• @SaSSafraS1232, you're confounding quarter-sawing (a process) with quarter-sawn wood (a product description). Quarter-sawn does not refer to how the board was created, although of course most QS wood will be created by deliberate quarter-sawing. But rift-sawing can easily produce quarter-sawn wood given the right variations in the original log and the reverse is also true — no matter which method of quarter-sawing is used some of the wood produced won't end up being QS because the grain slopes just that bit too much, so it'll be sorted into the rift-sawn stacks. – Graphus Jun 8 '18 at 15:58
• @SaSSafraS1232, ah OK fair enough. I took it as a given the heart would be cut out, leaving two boards that were QS or close. – Graphus Jun 8 '18 at 22:02