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

[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

[Jack Frederick]

If it has a swale it will also flex diagonally. I assume you have a preferred location to use as the assembly area. Roll it into your preferred position and check for level including the diagonals. I don't think a middle caster will give you an accurate surface. It might but I think I'd get a couple pieces of some pretty heavy angle iron. Get a 3/4" rod coupling and weld it between the angle iron. Run a 3/4' bolt up into the coupling and back it out to the floor for level. Set a jam nut and you are good to go. This whole assembly would only be in place when you need it. As it flexes under the load you might consider corner rods as well. I am not sure how often or far you move the table, but when I built my assembly table I skipped the casters and put legs capped with an HDPE foot. I can throw a nylon sling around the legs and drag that thing anywhere I need it, but I don't have a huge load on it.

[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.

[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.

[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...?

[Marc Fenneuff]

I like Robert's suggestion of both steel angle and 2 additional casters in the center.

I have a couple large (5-6') mobile saw tables/cabinets and they are both built atop a 4-1/2" high torsion box base. That plus casters mounted inboard instead of at the corners helps keep the base flat. I enjoy the construction method so much (I glue the rib intersections and do not cut notches) that I use it on all my mobile cabinets for consistency. So long as you account for the desired finished height, you can build whatever you want on top and re-purpose/reconfigure later on if your needs change.

That's a nice cabinet, hope you get it squared back up.

Edit: I had another thought, in case you are trying to stick with wood as opposed to metal. You could add ribs underneath. I cut stopped dadoes in the underside of the (very short) torsion box base for my cabinet saw, and glued ribs across the bottom.

20200621_iphone_0780.jpg 20200621_iphone_0782.jpg

[glenn bradley]

I did something similar to what Marc Fenneuff did above for my cabinet under my drum sander. Sander plus lots of abrasives equals a lot of weight. I made the ribs a bit shorter and added a bottom panel to complete the torsion "box" effect. It is so rigid that despite 350# of stuff on a plywood box it will lift a caster off the ground if I stop on an uneven spot on the floor. Empty your cabinet, flip it over, perform surgery, let the glue dry, flip back over and refill ;-)

torsion bottom.jpg

[Ron Selzer]

I would add a truss cable underneath about inch and a half back. Use a strip of wood across the middle a inch in height less than intended height. Use a turnbuckle to tighten the cable and raise center of the chest back up. Could do it with all thread also. Use two pieces that go from each end and meet in the middle. Use an angle iron in the middle of you use all thread.
Good luck
Ron

[Malcolm McLeod]

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

So I was up early and bored - -
I assumed some things: 6ft long cabinet; 300lb load (distributed); supports (casters) at the extreme ends; zero beam strength in the existing structure; and 2ea. angle iron beams. To keep it simple, I ignored the torque induced by the casters.

Using common steel angle shapes :: maximum expected deflection

• 2 x 2 x 1/8 :: 0.132"
• 2 x 2 x 1/4 :: 0.072"
• 3 x 2 x 1/4 :: 0.023"
• 3-1/2 x 2-1/2 x 1/4 :: 0.013"

As you can see, the extra depth makes a big difference. Weights range from 1.65 lbs/ft to 4.9 lbs/ft, and expect cost range to match.

IF this is a route you choose, maybe this will give you some idea of what the results might be.

(Its been a couple of years since I bought much steel, and I could not find 4x2x1/4.)

[Alan Lightstone]

I would add a truss cable underneath about inch and a half back. Use a strip of wood across the middle a inch in height less than intended height. Use a turnbuckle to tighten the cable and raise center of the chest back up. Could do it with all thread also. Use two pieces that go from each end and meet in the middle. Use an angle iron in the middle of you use all thread.
Good luck
Ron

Trying to get my head around this one, Ron. Can you make a rough drawing of what you are describing. I'm not sure how this connects to both ends of the cabinet.

[Alan Lightstone]

I like Robert's suggestion of both steel angle and 2 additional casters in the center.

I have a couple large (5-6') mobile saw tables/cabinets and they are both built atop a 4-1/2" high torsion box base. That plus casters mounted inboard instead of at the corners helps keep the base flat. I enjoy the construction method so much (I glue the rib intersections and do not cut notches) that I use it on all my mobile cabinets for consistency. So long as you account for the desired finished height, you can build whatever you want on top and re-purpose/reconfigure later on if your needs change.

That's a nice cabinet, hope you get it squared back up.

Edit: I had another thought, in case you are trying to stick with wood as opposed to metal. You could add ribs underneath. I cut stopped dadoes in the underside of the (very short) torsion box base for my cabinet saw, and glued ribs across the bottom.

20200621_iphone_0780.jpg 20200621_iphone_0782.jpg

Ribs don't need to be attached via stopped dados though, right? I could just screw full length ones to the bottom of the cabinet and it should still work. Correct?

[Alan Lightstone]

(snip...)

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

The reason I'd like to avoid moving in the casters is that I will lose the ability to lock them down if I do that.

And I'd like to avoid adding 2 casters in the middle as I find that they drag, not roll, most of the time as they don't spin in alignment with the outside casters. If people have had a different experience with that, I'd like to know, but I've been burned with that approach once before.