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Attaching apron to benches with some perpendicular grain

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Forum topic by Travis posted 09-18-2019 05:46 PM 286 views 0 times favorited 5 replies Add to Favorites Watch
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Travis

303 posts in 281 days


09-18-2019 05:46 PM

Hi all,

One of my last question posts for this built-in bench project, I promise!

I’ve got the structural carcass built and attached to the wall. I have some legs made for additional support (not included in the mock-up below), which will be attached to the carcass, not the benches. I have the two large bench panels built. What remains is joining the two bench sections and adding the aprons under the benches to hide the 2×4 carcass.

I know the text in the picture is small: Bench A is the long bench, and Apron A is its apron. Bench B is the smaller bench, its long apron is Apron B1 and the shorter apron is Apron B2. Apron B1 and B2 come together in Corner 1.

A few specific questions: Bench A and Bench B will be moving in opposite directions. Bench B’s movement against Bench A should be mitigated by leaving some space against the enclosing walls. Apron A and Apron B1 should not be in conflict because Bench A (and consequently Apron A) will move together as Bench B tugs it back and forth, correct?

Apron B2 will need to accommodate Bench B’s movement, but I don’t want to the lose the flush visible corner (Corner 1). I was thinking of attaching Apron B2 with pocket screws and wood glue on that left edge (Corner 1) where I want it to stay flush. Then could I use z-clips or other table top fasteners along the rest of Apron B2 to allow for Bench B’s movement?

Apron A and Apron B1 I planned to just use pocket screws and wood glue because they are not perpendicular to the grain they’re attached to.

Anything I’m missing?

Thanks a ton!

-- The plan is wrong; my finished piece is right.


5 replies so far

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Travis

303 posts in 281 days


#1 posted 09-18-2019 09:45 PM

I see there have been a lot of views but no comments yet. Perhaps my initial post included too much information, I tend to get over-analytical and obfuscate things.

My main question is how to attach the short apron that is perpendicular to the bench’s grain. I know standard practice when attaching something across the grain (e.g., battens, breadboards, etc.) is to secure in the middle and use flexible methods on the outsides where the movement is most likely to manifest. In this case I don’t want to do that because I will risk the visible corner joint becoming proud (that is, the bench and long apron will pull away from the short apron as the wood expands and contracts). So is it acceptable to securely attach at the visible corner and use flexible methods along the rest of the length so that the corner stays true as the bench expands and contracts?

-- The plan is wrong; my finished piece is right.

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Aj2

2499 posts in 2312 days


#2 posted 09-18-2019 09:52 PM

I think your over thinking it. The pieces are small as in not very thick and not very wide. So wood movement will be small.
Plus it’s a bench where people put their butts on it. Who’s going to eye ball your corners to see if they move one sixty fourth of a inch.

Good Luck

-- Aj

View Smitty_Cabinetshop's profile

Smitty_Cabinetshop

16194 posts in 3132 days


#3 posted 09-18-2019 09:55 PM

Apron A and Apron B1 should not be in conflict because Bench A (and consequently Apron A) will move together as Bench B tugs it back and forth, correct?

I shall venture forth and say, False. They won’t move together…

Remember that wood movement is predominately a cross-grain thing. And of course the wider the solid board, the bigger the potential movement. With your aprons fastened to not-very-wide boards (per the pic), wood movement (although a certainty) doesn’t appear to be a detrimental risk. Meaning, at the likely chance others will disagree vehemently, I’d say build it with stuff acclimated to the room and it should be good.

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive --

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Travis

303 posts in 281 days


#4 posted 09-18-2019 11:07 PM



I think your over thinking it. The pieces are small as in not very thick and not very wide. So wood movement will be small.
Plus it’s a bench where people put their butts on it. Who’s going to eye ball your corners to see if they move one sixty fourth of a inch.

Good Luck

- Aj2

I appreciate the feedback! I over-think a lot and I’m still fairly new to this so don’t always know when rules can safely be broken.


Apron A and Apron B1 should not be in conflict because Bench A (and consequently Apron A) will move together as Bench B tugs it back and forth, correct?

I shall venture forth and say, False. They won t move together…

Remember that wood movement is predominately a cross-grain thing. And of course the wider the solid board, the bigger the potential movement. With your aprons fastened to not-very-wide boards (per the pic), wood movement (although a certainty) doesn t appear to be a detrimental risk. Meaning, at the likely chance others will disagree vehemently, I d say build it with stuff acclimated to the room and it should be good.

- Smitty_Cabinetshop

The stuff has been sitting in my garage for a few months now, hasn’t spent much time in the actual room yet because whenever I put it there the kids can’t leave it alone. There’s a major temperature difference between the house and the garage (Phoenix summer), but probably not a big humidity difference (again, Phoenix…)

So some people think I shouldn’t worry about the wood movement, and just use glue and pocket screws on all the aprons? The benches are 18.5” wide.

-- The plan is wrong; my finished piece is right.

View bilyo's profile

bilyo

858 posts in 1617 days


#5 posted 09-22-2019 09:23 PM

From your drawing, it appears that the individual bench planks are not joined but, have small gaps between them. If you provide equal gaps at the walls and between bench A & B, you will not have any movement issues. The aprons all abut at the end of long grain and the long grain will have almost no movement. So, these joints should stay tight. Having said that, you don’t say how the 2×4 sub frame is made or how the top planks will be fastened to it. Since they will be made of different materials (I assume the subframe is construction grade 2×4s), I would provide for a small amount of differential movement between them. Don’t glue the top boards down (particularly the wide ones). Best to screw them from underneath through elongated holes (particularly the wide ones).

If I am wrong and the bench tops are edge joined then you might have slightly more concern. But, pretty much the same advice applies: Provide a gap at the walls and between the two benches and then fasten the bench top panels underneath with screws or z clips. There should be no issues with the apron. You can screw it or nail it but, I would not glue it. Also, let the top panels float free of the apron. Don’t fasten them together. I would provide a small overhang, but that is just my personal preference.

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