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I am aiming to cut a single piece of timber into 2, such that I can dynamically change the length by joining the pieces with screws. This would allow me to use a shorter piece of wood, rather than joining 2 longer pieces together. The following diagram shows the cut I attempt to make to do this:

Variable length wood

Just a couple of questions:

  • Is there a name for this type of cut?
  • Is it possible to cut this, what tools would be required?

Edit: Thank you for the responses, some clarifications:

  • Yes, I failed to account for the material lost due to the cutting process.
  • If this was constructed from 2 separate pieces of timber, there would be a wastage of the length of the cut in the grain direction. If cutting from a single piece, there would not be any wastage.
  • The purpose would have been to create a frame, such that the depth could be adjusted by unscrewing, sliding the wood and re-screwing onto a number of fixed holes. The load would have been on the ends, not on the joint in the centre.

I am now of the impression this is not practical to construct.

  • Welcome to WW.SE. Please take the time to take the tour and find out how SE sites work. Specifically, this is a reminder that this is not an internet forum, but rather a collection of questions and answers. – jdv Nov 23 '19 at 15:01
  • No you can't do this exactly as pictured from one piece of wood, partly because it doesn't account for the wood lost to the cut that parallels the two faces. Also doing this cut is very difficult anyway. Possibly the only way to do this with reasonable accuracy would be using a laser..... However you don't have to make this from just one piece of wood do you? What you want to end up with — the two pieces shaped this way — is what really matters doesn't it? – Graphus Nov 23 '19 at 17:41
  • So, I'm a little unsure of your objective. You're wanting to cut a somewhat long board into two shorter ones to make the whole thing permanently longer than the original board? ....or you essentially are looking to have a longer board that is adjustable? – Greg Nickoloff Nov 25 '19 at 17:43
  • Thanks for your update. But is there a reason you can't do this from two pieces of wood? Or to start with a longer single piece, cut it into two parts and then form the halving/lap portions which can then overlap? Is it a question of cost, continuation of the grain or something else? – Graphus Dec 11 '19 at 8:43
  • @Graphus You're correct, this can be done with 2 pieces of wood. My motivation was to use the wood efficiently with a special cut, as if constructed from 2 pieces, the total wastage would be the length of the cut, in the direction of the gain. – pymekrolimus Dec 11 '19 at 8:54
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It's unclear what you want to use this joint for, but that would be some kind of lap joint. It is cut the same way any "rebate" is cut: with machine tools like a saw or router, or with a hand saw. It depends on the dimensions you are thinking about, and the type of wood.

It would not be very strong in a few directions, though. Metal fasteners in wood are strongest in the shear direction, so this might be ok for minimal tension or compression loads. Though the failure mode would be sudden and catastrophic.

And loads perpendicular to that joint on any axis would fail almost immediately. This isn't really using wood in a manner that takes advantage of its strengths. If this "joint" was stiffened and strengthened by some other construction it might be ok, but since you do not show that here it's hard to imagine your application.

Maybe tell us what you are trying to achieve? If you want a sliding joint like those found in some tables, there are all-wood techniques for doing so. There are also hardware solutions that offer similar solutions.

If your question is about ways of combining multiple pieces of wood into single dimensioned pieces then, in general, this is not the way to go about it. Depending on the application, there are several well-tested traditional ways of doing this that trade-off strength, aesthetics, and skill required. As the engineering maxim goes: "Good, fast, or cheap; choose any two."

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