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How long would you make these slots?

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Forum topic by Mcpowell posted 04-27-2016 08:44 PM 416 views 0 times favorited 4 replies Add to Favorites Watch
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Mcpowell

8 posts in 357 days


04-27-2016 08:44 PM

I am building a solid walnut, live edge table. On the bottom side of the tabletop, I would like to use steel u-channels running perpendicular to the grain of the wood (would “ribs” be the correct term?). I will likely use 5 u-channels over the 90” length. The table will be about 50” wide. I will cut slots for the legs of u-channel and then attach the u-channels to the underside of the top with 3/8” bolts (screwing them into threaded metal sleeves).

My question is directly related to wood movement. It appears the width could grow close to an inch (that seems like a lot to me). Should the slots all be 1” long, as shown in my drawing?

And just to show you an example of what I’m trying to build…

-- I want to be good at this....


4 replies so far

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SCOTSMAN

5839 posts in 3053 days


#1 posted 04-27-2016 08:56 PM

One inch would allow for movement imho, or even less. I would do them only across the grain as wood is unlikely to move much along the length of it’s grain again IMHO.

For cutting slots in metal, a machinists milling machine would be best. For aluminium and other softer metals just try a router table. However if you have a machine shop neighbour or even commercial shop near to you, ask for a price if you were near to me I would do it for you for free. Alistair

-- excuse my typing as I have a form of parkinsons disease

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JayT

4788 posts in 1679 days


#2 posted 04-27-2016 09:05 PM

My question is directly related to wood movement. It appears the width could grow close to an inch (that seems like a lot to me). Should the slots all be 1” long, as shown in my drawing?

- Mcpowell

In the center of each rib, just have a hole, not a slot, so that the bolt locks in tight. This locks the center and forces any expansion to push to both sides. Then, as you move out, each successive slot will need to be a bit longer. If your 1in estimate is right (seems too much to me, as well), then the table could expand 1/2in each direction, so your very outside slots would need to allow for at least that much and the inner slots don’t need to be as long, though nothing is hurt by the slots being longer.

-- "Good judgement is the result of experience. A lot of experience is the result of poor judgement."

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Mcpowell

8 posts in 357 days


#3 posted 04-27-2016 09:11 PM

Thank you for the quick replies.

The center hole is a great idea. I’m glad I asked.

Alistair, I can actually have the u-channels cut on a laser and then the blanks bent on a press brake. It’s the business I’m in, so I have a nice advantage there. Thank you for the offer.

-- I want to be good at this....

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rustfever

716 posts in 2778 days


#4 posted 04-27-2016 09:40 PM

Uni-strut is what you are trying to create. Has already been invented.

Available at some Big Box Stores AND every electrical supply house. The slots are already cut/punched. Material comes in several sizes. I believe you would want .75” thick x 1.65”wide x 10’ [12ga.] Can be cut to any length. Available in mild steel, galv, and stainless steel and even epoxy coated.

Home Depot has 1.65” x 1.65” x 10’ [12ga] for less than 20$ each. Check around till you find the 1.65” x .75” x 10’ x [12ga]. This size is a standard, just not carried by HD.

-- Rustfever, Central California

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