What's the best way to fix this assembly table / cabinet?

[Alan Lightstone]

I built this cabinet last year, and it provides major storage for my shop. It lives on the left side of my SawStop ICS, and is slightly lower than the table saw height, so nothing catches.
Assembly Table - Cabinet 1.jpg
Assembly Table - Cabinet 2.jpg

It's large (both long and pretty wide).

The problem is, that it sags in the middle. Not a huge amount, but clearly enough to affect its use as an assembly table. So how do I fix this?

The cabinet is on 4" casters, as it does need to be moved if I want to run anything longer than 6' through my planer.

I've thought of replacing the casters with something smaller (? 3"), which would let me make a workbench top of 1.75" (It's 3/4" baltic birch plywood now). Perhaps end grain butcher block. Although that would be a ton of work and a beast to lift onto the table. And my wide-belt sander only goes up to 24" (my bad for buying the smaller model).

I've also thought of building a torsion box (but don't think I can generate enough additional height to do that).

The table top is now supported by a few vertical supports, and attached with L-brackets. I tried putting a screw jack under the middle of the table on the floor, but that doesn't seem to make things better.

[Jim Becker]

I will hazard a guess that the sag is because the base is thin for the span...not atypical for any piece of furniture of those dimensions. Try inverting the whole thing and adding heavy angle iron to the bottom to draw it flat with a little help from gravity and some bolts. You may want to let it sit for a few days upside down with some weight before making the final fix. As long as the angle iron (lengthwise) doesn't extend all the way to the floor, you'll not have to change your casters. Smaller casters are not necessarily a good thing for mobility, either.

[Paul F Franklin]

Guesswork on my part, but perhaps the bottom is sagging under the weight, so the top naturally follows? Could you add rails under the bottom (in the space made by the casters) to get the bottom as flat and rigid as possible, and then shim between the vertical dividers and the top to get the top flat again? You might even think about adding two more casters in the middle of the bottom, although that might make it more likely to rock unless your floor is really flat.

[Frederick Skelly]

Hi Alan,
I wasnt clear - does just the top sag, or is the entire cabinet sagging in the middle? I'm just brainstorming here but maybe it will give you or others ideas -

If the entire cabinet sags, I wonder if you could attach a couple pieces of angle iron along the full length of the bottom? Before bolting them in, I would clamp them firmly at each end to see if that actually helps (or not). EDIT: Looks like Mr Becker and I were posting the same idea at the same time. Sorry Jim.

If it's just the top, maybe you could put shims in the middle, between the top and the cabinet? Again, Ixd clamp both ends to see if this helps, before making permanent changes.

Good luck,
Fred

[Alan Lightstone]

Hi Alan,
I wasnt clear - does just the top sag, or is the entire cabinet sagging in the middle? I'm just brainstorming here but maybe it will give you or others ideas -

If the entire cabinet sags, I wonder if you could attach a couple pieces of angle iron along the full length of the bottom? Before bolting them in, I would clamp them firmly at each end to see if that actually helps (or not). EDIT: Looks like Mr Becker and I were posting the same idea at the same time. Sorry Jim.

If it's just the top, maybe you could put shims in the middle, between the top and the cabinet? Again, Ixd clamp both ends to see if this helps, before making permanent changes.

Good luck,
Fred

Actually, I just measured the bottom, and the middle of it is sagging 1/4", so pretty substantial.

I do have full length angle iron on the bottom, on both the front and back of the cabinet.

Jacking it up and putting a box plinth (had to look that up), under the middle is an idea, but I would have to jack it up to remove it when moving the cabinet, so kinda involved. I do have a car jack that could do that, but it isn't stored in my workshop.

[Malcolm McLeod]

Actually, I just measured the bottom, and the middle of it is sagging 1/4", so pretty substantial.

I do have full length angle iron on the bottom, on both the front and back of the cabinet.

Jacking it up and putting a box plinth (had to look that up), under the middle is an idea, but I would have to jack it up to remove it when moving the cabinet, so kinda involved. I do have a car jack that could do that, but it isn't stored in my workshop.

Plinth would be permanently attached, then use workbench casters (had to look that up!!).

Not sure what your weight requirements are, so this may be a long shot too? ...Just throwing ....uhhhm... things, at the wall to see what sticks.

[Alan Lightstone]

Plinth would be permanently attached, then use workbench casters (had to look that up!!).

Not sure what your weight requirements are, so this may be a long shot too? ...Just throwing ....uhhhm... things, at the wall to see what sticks.

I won't have access to the back center of the cabinet, so those workbench casters won't work here. They do work great on my workbench, BTW.

I just found that any conventional rotating casters in the middle of a heavy long cabinet don't follow the pattern of the outside casters, so you are kinda dragging the cabinet when you use 6 of those.

[Kevin Jenness]

If the only reason for moving the cabinet is planing long material, how about raising the planer? Then you could set the cabinet on the floor and put a torsion box on top of it.

[Andy D Jones]

Assuming your drawers are full depth, you don't have a vertical, full length strongback in that structure. If the drawers were half-depth, with a second set of drawers on the back side (for seldom-used stuff), then you could have a vertical center spine of 3/4" ply running lengthwise down the middle, and have plenty of rigidity lengthwise.

What size angle-iron do you have under it now? I would think 2" real angle-iron (not that stamped and bent sheet metal crap) would be enough, and use two, full length, far enough in from the sides so they don't interfere with the casters' swiveling.

Otherwise, since you have ~4" casters under it, you should have room for almost 4" deep vertical beams, glued and screwed into 1/2" deep, snug dadoes running the length of the bottom. I'd use 4 or more. 3/4" thick is fine.

-- Andy - Arlington TX

[Alan Lightstone]

If the only reason for moving the cabinet is planing long material, how about raising the planer? Then you could set the cabinet on the floor and put a torsion box on top of it.

Really interesting idea, Kevin. But how to attach a torsion box to the sagging top?

[Kevin Jenness]

"how to attach a torsion box to the sagging top?"

Just set it on there. Shim as needed and screw from below or set it on dowel pins.Get rid of the existing top if you want.

[Frederick Skelly]

Actually, I just measured the bottom, and the middle of it is sagging 1/4", so pretty substantial.

I do have full length angle iron on the bottom, on both the front and back of the cabinet.

Man that's a bummer and I bet that sag is only going to get worse. That cabinet is too nice to leave it untreated. I found this 2"x2"x1/4" angle iron at Granger. It's pricey, but I'd be pretty surprised if it sagged once you bolt 2 of these on.

Good luck. Please let us know what you decide to do.
Fred

[Alan Lightstone]

I'll have to measure the angle iron. It's the Home Depot stuff, so probably not nearly sturdy enough.

[Jim Becker]

I'll have to measure the angle iron. It's the Home Depot stuff, so probably not nearly sturdy enough.

I'm thinking the heavier 2" angle of the thicker material for this kind of application.

[Malcolm McLeod]

I'm thinking the heavier 2" angle of the thicker material for this kind of application.

I still don't know Mr. Lightstone's load requirements, but based solely on his statements about existing deflection and assembly usage, I'd recommend 2, or even 3, 'keels' of 3x2x1/4 A36. Should run about $35 for a 6ft stick (online), maybe less if the local steel yard can convince him to take the whole 20ft stick?

And I'd still move the casters 'in' at least 8-9" to shorten the span. - YMMV

Perfection can be pricey!

***
I might even use 4x2x1/4, IF the casters allow clearance for it...?