Need Advice Mounting the Workbench Top

[Geezermag]

Hello all,

I’m looking for some design review on mounting my workbench top to its base.

I’ve been working on building my workbench. The top is 3”-1/4 x 33”x79” Roubo-style lamination of SYP, while the base is a hydraulic scissor-lift table. The lift table has a 1/2” thick, 30”x30” steel plate welded on, with thinner sheet metal welded to an angle frame about 50” long.

In fastening the top to the base, I want to maintain air flow across the bottom, as well as allow for expansion and contraction.

My understanding is that the best practice for screwing a top like this down is that I should screw tightly into the center of the expansion direction, fit into a slip-fit hole, then snugly screw along the direction of expansion with screws fitted into slots.

Since I don’t have a headache-free way of slotting the 1/2” steel plate, and I want to keep some airflow, I’ve decided to screw some mounting pads into the top, then attaching those to the steel plate with threaded inserts so everything is removable.

It seems that this solution will feed two birds with one scone, but I’d love some feedback if I’m missing something. Concept below.

 

[JNCarr]

That should work fine. A comment about the facia that extends below the bottom of the table - if you ever want to clamp something to the bench your clamp positions will either be limited by the facia or have to use culls on the other side of it.

 

[Geezermag]

That should work fine. A comment about the facia that extends below the bottom of the table - if you ever want to clamp something to the bench your clamp positions will either be limited by the facia or have to use culls on the other side of it.

I thinking I will add blocking behind the skirts for this reason. in the center section of the bench, the steel plate is so wide that I cannot sneak a clamp between it and the workbench without everything looking wonky.

That being said, I would only need the blocking in the overhanging sections. I’ve not mounted my vises yet so I intend to just add that blocking after the fact when everything else is squared away.

 

[mkepke]

Drilling a 1/2” steel plate a bunch of times doesn’t sound like a lot of fun to me. And you’re having to try to engineer around it.

Can you remove the steel plate altogether?

-Mark

 

[Geezermag]

Drilling a 1/2” steel plate a bunch of times doesn’t sound like a lot of fun to me. And you’re having to try to engineer around it.

Can you remove the steel plate altogether?

-Mark

Drilling the holes is trivial in comparison to cutting the plate off.

As a plus, the added mass and rigidity from the weldment is welcome.

 

[Jack A.]

Sounds like a really good excuse to buy a new tool...

Oxy-acetylene torch? Plasma cutter?

 

[mkepke]

Drilling the holes is trivial in comparison to cutting the plate off.

As a plus, the added mass and rigidity from the weldment is welcome.

Looks like a couple of 1" spot welds on each side? If so, should be easily cut with a cutting wheel in an angle grinder, but obviously your call.

The hydraulic lift table is cool.

-Mark

 

[Darl Bundren]

Here's what I'd do. Mount two wooden rails nearly the length of the top (don't interfere with vise placement, though). Bolt them to the steel top using probably three bolts per rail, washers underneath, stout screws or lag bolts. On top of the rails rout out recesses to hold metal clips you can easily fabricate if you can cut and drill steel. I got mild steel from the big box and had them done easy peasy. Screw the clips to the rails in the recesses. Place the top on the rails and screw the other ends of the clips to fasten the top down. It should be plenty strong, easy enough to do, and the top will be able to move because the clips with shift with expansion. Kind of like fastening a table top using figure 8 clips, but larger scale. I did my workbench this way hooking the top to the legs, and your application seems similar.

You could probably do without the rails, but I think having support for the overhangs may be useful when you're unleashing the fury on some project or another. If you do attach rails make sure the bolts don't interfere with dog hole placement if that's in your plans.

Regardless of what you do, good luck with it! That's going to be tight when you're done.

 

[Gotcha6]

Keep in mind that when you are banging on a piece of wood with a chisel on the ends of the top, it's going to stress the fasteners on the opposite end and try to strip them out. Make your connection as close to the end of the bench top as practical and use multiple fasteners. If you're concerned with movement of the wood itself, invest in some figure 8 washers let into the sub top and screwed to the top itself.

 

[Geezermag]

Keep in mind that when you are banging on a piece of wood with a chisel on the ends of the top, it's going to stress the fasteners on the opposite end and try to strip them out. Make your connection as close to the end of the bench top as practical and use multiple fasteners. If you're concerned with movement of the wood itself, invest in some figure 8 washers let into the sub top and screwed to the top itself.

This its exactly the kind of advice I was hoping for. I’ve seen enough folks recommend long rails, I think Im going to take that route.

 

[Wilsoncb]

I would essentially clamp it to the plate. Saves drilling the plate and allows for wood movement.

 

[mkepke]

I would essentially clamp it to the plate. Saves drilling the plate and allows for wood movement.

I normally favor the same thing – but that steel plate is too wide so edge-clamps will conflict with the apron on his wooden top (you can see it in the diagram he posted).

-Mark

 

[JohnnyR]

My thoughts: first I would rout out the apron so that the bottom of the plate is flush with the apron and reduce the depth of the maple strip (clamping problem solved locally). Make a dowel that fits snugly in the center hole of the plate and a hole in the underside of the bench top (first adding a spacer same as maple strip. Fashion some "Z" clips similar to Wilsoncb or out of metal and you only have to put them on the sides with a screw. Whatever you do it's going to be a nice bench!