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Joinery workbench apron & table wood movement question

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Forum topic by Holbs posted 02-13-2018 12:43 AM 1126 views 0 times favorited 6 replies Add to Favorites Watch
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Holbs

1796 posts in 1935 days


02-13-2018 12:43 AM

Here is my theoretical rendition of what I believe I must do to tackle wood movement due to humidity and seasonal changes in the 2”x12” cut in half douglas fir table top to hard maple apron. I have read a lot about the need to address wood movement for workbench tops with elongated drawbore pins, bolts, etc. Does this sound/look correct?
1.) floating mortise & tenons. Only the first board of the 4 group gets pinned & glued, the following 3 will be floating tenons in a mortise not to be glued or affixed to anything in the mortise.
2.) there is a 1/2” gap between the 3 groups of 4 for temporary saw blade and chisel storage while working and wood expansion.
3.) A tool well in the back.
4.) All measurements and configuration of a joinery bench top is subject to change as I have only dimensioned the 3 groups of 4 so far.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter


6 replies so far

View jmos's profile

jmos

820 posts in 2275 days


#1 posted 02-13-2018 12:44 PM

I can’t say I’ve seen this approach before, but it looks to me like it will work. You’re giving the table top sections room to move, which is the goal. Good luck with the new bench.

-- John

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jdh122

983 posts in 2723 days


#2 posted 02-13-2018 01:26 PM

I apologize in advance in case if I misunderstand your approach..
If each “group” is only 6 inches wide you can glue them in place. Quartersawn douglas fir is one of the most stable woods that exist and will give you no problems over that width, assuming each 4-piece group is separated from its neighbour. That said I personally would not want those long cracks down my workbench. Partly cause of things getting stuck in them and partly because it complicated attaching it to the structure, as you don’t want all the weight of the middle groups to be resting on their tenons (but you’ve probably figured out a way to attach the top).

-- Jeremy, in the Acadian forests

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JBrow

1327 posts in 825 days


#3 posted 02-13-2018 01:31 PM

Holbs,

Your design should accommodate any expansion or contraction of the top within the maple border. However, the gap between each group of four may expand or shrink with seasonal movement. This movement could render the gap unsuitable for tool storage from time to time by being either too wide or too narrow; depending on the amount each group of four expands or shrinks and the initial size of the gap. The design would require a base that fully supports the top; otherwise there would be a tendency for each group of four to rotate if not fully support from below.

The bottom of the tool tray could be an impediment to expansion of the top. Therefore the design of the bottom of the tool tray should allow the adjoining group of four some room for expansion while ensuring that contraction of the adjoining group of four does not create a gap between the bottom of the tool tray and the adjoining group of four.

I assume the top will be attached to the base so that the expansion and contraction of the top is accommodated.

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Holbs

1796 posts in 1935 days


#4 posted 02-13-2018 02:44 PM

Jeremy… I am taking experience from joinery work (pounding chisels) from my current lightweight rickety workbench. Grabbing and setting down saws & chisels that roll around or flee on their own accord is always a nuisance, so having something akin to roubo workbench tops with a gap in the middle seemed to be the answer. I went with 2 gaps instead of 1 only because of being variable in the work piece being worked on and it’s depth. This might change as I am near the deciding stage. Might go for 1 gap. And yes, there will be underneath of table horizontal supports. Most pounding will occur in the first 4” or so towards the front when it comes to chisels.

Jbrow, yes there will be full underneath support.
Oh..forgot to mention, there will be a Benchcraft moxon vice on the front of this as well :)

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

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Rick_M

11109 posts in 2285 days


#5 posted 02-13-2018 04:43 PM

What is the thought process behind doing it this way? It looks unnecessarily complicated to solve a problem that has been solved in simpler ways.

-- http://thewoodknack.blogspot.com/

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Holbs

1796 posts in 1935 days


#6 posted 02-13-2018 09:27 PM

Rick… ya.. the more I think about it, I am making this too complicated. The only reason I considered to have 2 gaps of 1/2” was for chisel / saw blade temp storage while working. I am reading The Schwarz book now on work benches and I’ll probably ditch the idea and go 1 full piece instead of 3 sections with a gap. I can always add drawers underneath for hand tool storage.
So with that said… to correctly tackle the wood movement, I only pin & glue the first board to the front & side apron, the other 11 boards are floating tenons in the side apron mortise? There will be a tool well in the rear to allow for wood expansion.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

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