This obviously depends on the thickness of the wood. When you see multiple splines on a join they use contrasting wood colors to create a nice effect. But is that the only reason? Consider the following picture:

Spline Join

Image from CanadianWoodworking

Would it be preferential, for the strength of the joint, to have one large spine that spanned the space between the outer splines of the picture above?

2 Answers 2


Joints increase in strength with the cross-grain surface area. This is the sides of the spline.

That means more splines is better.

However, too much of a good thing is bad. At some point the cuts you need to make for the splines will weaken the wood too much.

  • 1
    Is it possible to take that logic too far? Using the same splines in the picture I could easily double the splines that are there. Not that it is realistic to do
    – Matt
    Commented Apr 24, 2015 at 15:07
  • 1
    Along the lines of your edit, I would think once you get past the point of the cross-grain surface area being beyond 1/2 the thickness, you've gone too far. Commented Apr 24, 2015 at 15:12

As rachet freak said, the primary reason for splines is to increase the gluing surface area. So having 3 small splines is going to give you more surface area to glue than one wide one, the wide one will give only slightly more area than a small single one.

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    And most of the area you get will be end-grain, just the same as if you didn't have a spline. Commented Apr 24, 2015 at 15:16
  • @ratchetfreak very true!
    – bowlturner
    Commented Apr 24, 2015 at 15:33

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