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I like pocket holes as it is a simple and easy method of joinery. I ran into plans for a farmhouse table that is nearly solely built with pocket holes. The following is the step where the table top is made. This showcases the use of pocket holes and the top's overall design.

Table top plan

Image from ana-white.com

Now, I have seen in several places warnings in regards to breadboards and several suggestions to mitigate inevitable wood movement.

Is this design begging for future problems? Are those problems minor and the top should be just fine?

  • Already answered Matt. – Graphus Apr 11 '16 at 7:36
  • @Graphus I was bound to ask a dupe eventually. I'm sure I can find another ana-white design to nitpick – Matt Apr 11 '16 at 11:43
  • Though similar to the earlier question, it is enough different to have inspired a different set of answers. – Ast Pace Apr 11 '16 at 15:18
  • Vote to reopen. There is a difference in the conditions in this question due to the breadboard end. It creates a different set of problems to resolve. – Ashlar Apr 11 '16 at 15:41
  • @Matt, "I'm sure I can find another ana-white design to nitpick" yes, I don't think that would be hard! But the problems do tend to be very similar in theme.... – Graphus Apr 11 '16 at 17:07
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Expansion/contraction-wise, I do not believe that securing of the five boards running end to end will cause a problem. This is basically the same condition as if they were glued together, their primary movement will be to expand and contract towards and away from the center to the sides of the table top. A problem could arise where the breadboards are secured to the ends of the table top boards. Since the table top and the breadboards at each end are oriented perpendicular, their movements will oppose each other. (Boards expand along their length at a much smaller rate than across their width or height)

Breadboards are basically secured firmly to the top only at the center. The boards at each side of the center are held in place vertically in a keyway (or by using biscuits etc.) and allowed to slide in the breadboard to and from the sides. The ends of the breadboard are secured to the table with screws in slotted openings so that some lateral movement is still possible.

In order to work well, the expansion of the table top boards must be accommodated within the individual pocket holes of the breadboard. The center of the breadboard is firmly affixed to the breadboard and movement occurs towards the sides. In fact the maximum movement occurs at the outside edges. The total expansion across the top will be from the center to each edge or approx. 19" of wood width. Figuring a little conservatively the expected expansion here would be 14" x 5 (percentage range of moisture variation) x .003 (expansion coefficient from wood tables online) = .21" or slightly less than a quarter inch on each side (nearly 1/2" across the width). That means that the pocket hole at the outside edges must allow for up to 1/4" of movement in the hole in the breadboard, which is a lot. Note that the breadboard edges must be long enough to absorb this width expansion. Now the screws at the sides will be able to turn at an angle within the pocket hole in the breadboard, but the movement at the edges will be enough to shift the shaft of the screw beyond the edge of each pocket opening. If the screw strikes the side of the pocket hole it will resist further shifts as the top expands.

Some other considerations that might help the detail include:

  • Use a wood type with lower expansion coefficient than .003, The table below is taken from popular woodworking.com at this link. Note that Q/S is the coefficient across the growth rings and F/S is with the rings.

Wood Table

  • The humidity differential of 5% reflects a total variation in humidity expected in its final location. If it is going to be in an air conditioned environment it may have lower variations.

  • Do not assemble the table when humidity is at the highest or lowest points. This will maximize the overall expansion and contraction. If it is assembled at its middle range it will still have the overall movement calculated, but only half in each direction. In our calculations above this would result in a movement of 1/8" each way at the sides of the table.

Also keep in mind that the movement range occurs seasonally and the joints will have a tendency to work further loose over time. Screws in the wood will not provide as good a connection as a traditional breadboard detail. In addition the screws will not resist the tendency of the top to warp and curl as well. The slotted connection of a traditional breadboard provides continuous alignment of each board in the top. The screws can only hold alignment at screw locations so cupping of individual boards in the top will eventually show themselves. That is unless you provide a slotted groove in the breadboard and tongues in the top board edges. In that case you are almost all the way to a proper breadboard anyways, so why not complete it as such?

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Is this design begging for future problems? Are those problems minor and the top should be just fine?

I looked at this design for a while, wrestling with the usual concerns about breadboard construction (crosswise expansions putting undue stress every which way), and concluded that the answer to your question is, not necessarily. I think that if you assemble the table with the knowledge that the boards are going to change in width due to changes in humidity, you can make this table so that it will not tear itself apart.

  • Make it in late summer when the humidity is high and the boards are going to be at their maximum width.
  • Attach each lengthwise board to the breadboard ends with only one screw at each end. This allows each board to shrink without putting any stress on itself or its connections. It's only going to get narrower than when it was built.
  • Do not drive the screws that hold the lengthwise boards to one another all the way in. When the boards shrink a small gap will open between the boards, but screws will keep the boards aligned. The only function of those boards is to maintain alignment.

Notice the picture of the completed table that accompanied the plan. The near breadboard end is sagging and if you try to rely on the pocket screws without supporting the ends, the screws will most certainly bend and allow the breadboard end to sag.

You end up with a table with sagging ends, visible slits between the boards (makes clearing crumbs real easy). However, recognizing that it is meant to be a rustic appearing piece of furniture, put a checkered tablecloth on it and love it.

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    Your one screw per plank idea won't mitigate the problem as the field of the table will still move as a single piece. This should apply even if no glue is used on the the longitudinal joints. The fixings therefore have to be thought of in relation to that one wide board, not the individual planks it is made from. Good to try to think around the problem but with problem areas on Ana White plans best practice is to throw them out entirely and start from scratch, i.e. hit the woodworking books and see how something should be done and use that as the new starting point :-) – Graphus Apr 11 '16 at 7:45
  • @Graphus, My suggestion not to drive the screws home is meant to allow the seam between longitudinal boards to open as necessary, assuming that the unthreaded portion of the screw near the head allows wood movement. If the screw is threaded full length from tip to head, then we have a problem. I don't know Ana White, so will rely upon your experiences her/him :) – Ast Pace Apr 11 '16 at 15:02
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Is this design begging for future problems? Are those problems minor and the top should be just fine?

Yes, it's a problem, and no, it's not minor problem. The whole point of traditional breadboard construction is to keep the table top flat while still allowing it to expand and contract across its width. A 30"-wide panel could easily expand or contract by 1/4" or more seasonally. Attaching the "breadboard end" with pocket screws prevents that movement and will cause the panel to crack over time.

Pocket holes can be a great shortcut, but sometimes you save more by spending a little extra time to do the job properly. This is one of those cases. Using a router, it doesn't take that much time to form a proper breadboard joint, and the final product will be a big improvement over the pocket hole version.

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