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Building a Workbench(Expansion/Contraction questions)

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Forum topic by Chris322 posted 08-26-2017 09:41 PM 1358 views 1 time favorited 11 replies Add to Favorites Watch
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Chris322

3 posts in 51 days


08-26-2017 09:41 PM

Topic tags/keywords: bench expansion contraction maple butcher block tip

I have 20+ years as a cabinetmaker and know that expansion/contraction must be considered when building a butcher block style workbench. I have a large pile (500 to 750 bd ft) of home sawn maple that I cut down to build my new garage/shop two years ago. The moisture is finally low enough that I can start cutting it up 8% to 12%. I will be using mortise and tennon on the legs with wedges from the end to tighten them plus polyurethane glue on everything. The top will end up being 2 1/4” to 2 3/8” thick.

1. I have noticed that threaded rod is used quite often through the core of the table top. Is this for gluing purposes or does it eliminate expansion across the width of the table?

2. I want to place an endcap to cover up engrain but experience tells me that if I glue it that something is going to give/break when the wood expands/contracts.

3. If you have any suggestions on what mistakes not to make let me know. Haha weve all made them and learned from them.


11 replies so far

View jonah's profile

jonah

1245 posts in 3076 days


#1 posted 08-26-2017 11:01 PM

1) If the top is edge grain, the direction of expansion will be up and down. Wood doesn’t move much across the grain or in length. I can’t speak to how people use threaded rod because the only way I’ve used it on a workbench is to join the long stretchers to the leg assemblies.

2) You could use something like a breadboard end, but you’d need to take care in how you attach it. Remember, the edge grain glue up will move up and down. Personally, I wouldn’t bother, but your mileage may vary.

3) I wouldn’t bother with polyurethane glue. It’s messy as all get out and ordinary yellow glue is perfectly fine for a bench top lamination.

View Rich's profile

Rich

1669 posts in 367 days


#2 posted 08-26-2017 11:10 PM



1) If the top is edge grain, the direction of expansion will be up and down. Wood doesn t move much across the grain or in length. I can t speak to how people use threaded rod because the only way I ve used it on a workbench is to join the long stretchers to the leg assemblies.

2) You could use something like a breadboard end, but you d need to take care in how you attach it. Remember, the edge grain glue up will move up and down. Personally, I wouldn t bother, but your mileage may vary.

3) I wouldn t bother with polyurethane glue. It s messy as all get out and ordinary yellow glue is perfectly fine for a bench top lamination.

- jonah

#1 isn’t entirely true. Wood does move radially, but less than tangentially. According to the wood database, the ratio is about 2:1 for tangential to radial for hard maple.

A big +1 on #3. Poly glue is very weak, in addition to being a complete mess like Jonah said. You have to dampen one side of the glue up, and it foams and sticks to everything. If you’re concerned about moisture for some reason, go with DAP Weldwood plastic resin glue. It’s strong and durable and cleans up with water easily before it cures.

-- No matter how much you push the envelope, it'll still be stationery.

View jdh122's profile

jdh122

943 posts in 2595 days


#3 posted 08-26-2017 11:41 PM

If you have perfectly flatsawn wood, it’ll be quartersawn on the edges and will therefore move about half as much over its thickness as over its length. More likely the wood will be somewhere between quarter- and flat- and so will move a bit more than the tangential rate and a bit less than the radial rate, on average. But this is still too much across the width of a workbench to glue an endcap across the whole end. I think the traditional way to do a workbench with an endcap is to do a large sliding dovetail, presumably only glued in the middle. I’ve never really thought it was necessary.
I don’t think that threaded rod will reduce expansion-contraction by very much.

-- Jeremy, in the Acadian forests

View JackDuren's profile

JackDuren

315 posts in 737 days


#4 posted 08-27-2017 12:26 AM

They used a lot of threaded rod back in the early 80’s, Not 100% sure to all the reasons. Don’t see it now but haven’t bought a pre made top in many moons.

My top is 8/4 hickory without breadboard end. If it’s fastened correctly it won’t cup…

View JBrow's profile

JBrow

1233 posts in 698 days


#5 posted 08-28-2017 03:24 AM

Chris322,

1) I am not sure why threaded rods are installed in some work benches. Perhaps as you suggest; to help with the glue-up. However, I would think that the nuts securing the threaded rods would work loose over time due to expansion and contraction of the top.

2) A properly installed breadboard would conceal the end grain of the bench top. But one potential problem with a breadboard end is that it may stand proud of the bench top edges during times of lower humidity and the bench top long edges could stand proud of the breadboard end during periods of higher humidity. This would be due to the bench top expanding or contracting across its width while the breadboard length would remain almost unchanged. The extent to which the breadboard would not line up with the long edges of the bench would depend on humidity, the finish applied to the bench top, and the width of the bench top. I would guess the extent of misalignment would be unlikely to exceed ¼”.

3) Perhaps some obvious suggestions already considered are to ensure the height of the workbench works well with other tools in the shop and is at a comfortable working height. Once the bench top is glued together, spending as much time as needed to get the bench top dead flat would be appreciated later on. Allowing the bench top to overhang the leg assembly enough so that work pieces can be clamped to the bench top at the edges would come in handy from time to time. Lastly, if the work bench will set on castors for mobility, installing castors that are double locking with plenty of load capacity should last longer and function better than less expensive castors.

View rwe2156's profile

rwe2156

2658 posts in 1258 days


#6 posted 08-28-2017 02:52 PM

Eliminating the end cap will eliminate your worries about that.

You shouldn’t have too much to worry about just make sure you allow for movement when attaching to base.

-- Everything is a prototype thats why its one of a kind!!

View Bluenote38's profile

Bluenote38

173 posts in 166 days


#7 posted 08-28-2017 04:59 PM

I’ve built several benches and never worried about expansion/contraction due to moisture. I’ve mostly used laminated pine (2×4 or 2×6) with some maple and walnut. Pine sucks water like a sponge but with a good sealer coat the wood won’t absorb enough to make a difference even when I was in Memphis TN it didn’t affect it especially considering that it’s 3’ to 5” thick. This might not be true for Houston today however.

-- Bill - Rochester MI

View Loren's profile

Loren

9411 posts in 3426 days


#8 posted 08-28-2017 06:18 PM

If you wanted a European style work bench top,
like the skirted ones from Scandinavia, you’d
build a tool tray into the back of the bench
and put skirts around the whole thing. My bench
is made like this.

http://lumberjocks.com/Loren/blog/27597

View Bill White's profile

Bill White

4764 posts in 3738 days


#9 posted 08-28-2017 06:44 PM

No poly glue.
My bench is made from bowling alley, has aprons and end caps. Yellow glue and screws with plugs. No movement in over 20 years.
Hey! I’m in Mississippi. Wanna talk about humidity?
Bill

-- bill@magraphics.us

View Chris322's profile

Chris322

3 posts in 51 days


#10 posted 08-29-2017 12:29 AM

Thanks everyone. There was a lot of good advice there that is greatly appreciated. I will skip the poly glue and just stick to yellow. I decided to skip the end caps. Now to finalize my design…....

View Chris322's profile

Chris322

3 posts in 51 days


#11 posted 08-29-2017 12:31 AM

Thanks everyone. There was a lot of good advice there that is greatly appreciated. I will skip the poly glue and just stick to yellow. I decided to skip the end caps. Now to finalize my design…....

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