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

  1. #1
    Join Date
    Jan 2010
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    What's the best way to fix this assembly table / cabinet?

    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.
    - I have enough frequent flyer miles to orbit the sun. Sigh...
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off.
    - When you earnestly believe you can compensate for lack of skill by doubling your effort, there's no end to what you can't do

  2. #2
    Join Date
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    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.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
    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.
    --Certainty is the refuge of a small mind--

  4. #4
    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
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  5. #5
    You've built a beam - even tho' it has drawers in it. The beam doesn't have enough section modulus for the span and the weight its carrying.

    As other have said, you can try increasing the modulus:
    - The only real contributor to the modulus of the existing 'beam' is the back panel. What is it made from? You could try doubling up this back panel (but, also as others have suggested, get the box straight first). Put enough screws/glue in to make sure it is effectively 1 piece. (Kind of a long shot; the front may still sag.)
    - Add angle iron between the casters ('keels'). If you can get un-equal leg angle (i.e. 2x3 or 2x4), make sure to install it with the 'longer' leg down; it will have greater modulus. It's why joists are 2x10, not 10x2.

    Or, you can try to 'shorten' the span of the beam:
    - Put full-swivel casters in the middle; cut the span in half. ...again, how flat is your floor?
    - Move the existing casters toward the middle (...1/4 of the length :: effectively cuts span in half). If the beam is too weak, this may just create a roller coaster - - still requiring a stiffener (i.e. angle iron keels) and run them full span.

    TMI? (You are now a member in good standing of the Reverse Engineered Structural Correction Union Escadrille)
    Last edited by Malcolm McLeod; 10-15-2020 at 11:30 AM. Reason: typo

  6. #6
    1. Angle iron underneath the bottom
    2. Extra casters in middle.

  7. #7
    Another idea....maybe?

    If you don't move it often, take the existing casters off and put a simple box plinth (4" high?) under it - avoiding the caster mounting locations. Then install leveling casters.

    Assuming the floor is relatively flat, the plinth will spread the weight and should allow the structure to 'creep' back to flat/straight..??

    Then jack the leveling casters down only when you need to move it.

    *********
    Edit: not 'levelling' caster, but rather the foot-operated type (proper name escapes me).
    Last edited by Malcolm McLeod; 10-15-2020 at 1:14 PM. Reason: cerebral flatulence retraction

  8. #8
    Alan,
    I recently used the angle iron trick on a Boramate setup for my tablesaw. It worked well so I would second the suggestions for that. If you put it in from the front & back a little it won't be a toe kick blocker. Additionally, the suggestions for a second set of casters will also help. If you're ambitious you could install all the casters on the angle iron. Nice table otherwise. Someday I'll build one similar

  9. #9
    Join Date
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    Elmodel, Ga.
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    My first thought was to put extra casters on it. Possibly 2 in the middle or even 4 dividing the span into thirds. Angle iron would be a plus too.
    SWE

  10. #10
    Join Date
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    I actually have two full length angle irons underneath the cabinet. It's certainly possible that it's not heavy/large enough angle iron. It is full length, though.

    One near the front of it and one near the back. In the middle the sag is roughly 1/16 of an inch perhaps a little larger.

    I once built a heavy cabinet with six casters, two in the middle. It was a bear to move. Is there a particular kind of caster kind of like a ball that would help with that?
    Last edited by Alan Lightstone; 10-15-2020 at 1:23 PM.
    - I have enough frequent flyer miles to orbit the sun. Sigh...
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off.
    - When you earnestly believe you can compensate for lack of skill by doubling your effort, there's no end to what you can't do

  11. #11
    Join Date
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    Location
    Tampa Bay, FL
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    2,339
    Quote Originally Posted by Frederick Skelly View Post
    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.
    - I have enough frequent flyer miles to orbit the sun. Sigh...
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off.
    - When you earnestly believe you can compensate for lack of skill by doubling your effort, there's no end to what you can't do

  12. #12
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    2,339
    Quote Originally Posted by Malcolm McLeod View Post
    You've built a beam - even tho' it has drawers in it. The beam doesn't have enough section modulus for the span and the weight its carrying.

    As other have said, you can try increasing the modulus:
    - The only real contributor to the modulus of the existing 'beam' is the back panel. What is it made from? You could try doubling up this back panel (but, also as others have suggested, get the box straight first). Put enough screws/glue in to make sure it is effectively 1 piece. (Kind of a long shot; the front may still sag.)
    - Add angle iron between the casters ('keels'). If you can get un-equal leg angle (i.e. 2x3 or 2x4), make sure to install it with the 'longer' leg down; it will have greater modulus. It's why joists are 2x10, not 10x2.

    Or, you can try to 'shorten' the span of the beam:
    - Put full-swivel casters in the middle; cut the span in half. ...again, how flat is your floor?
    - Move the existing casters toward the middle (...1/4 of the length :: effectively cuts span in half). If the beam is too weak, this may just create a roller coaster - - still requiring a stiffener (i.e. angle iron keels) and run them full span.

    TMI? (You are now a member in good standing of the Reverse Engineered Structural Correction Union Escadrille)
    LOL to the "Rescue".

    Simplest approach may be adding the casters to the middle. The floor is a raised access floor. Reasonably flat, but there are seams every 24" between metal panels. The four casters roll well on it, so fortunately probably not an issue.

    Full swivel casters really worked very poorly the last time I used 6 casters. I think ball transfer bearing units would be my best approach there, but they can be very pricey. I have to see if I can find 4" ones.

    Something like this?? https://www.vxb.com/551-lbs-Load-Cap...ransfer-fl.htm
    Last edited by Alan Lightstone; 10-15-2020 at 1:43 PM.
    - I have enough frequent flyer miles to orbit the sun. Sigh...
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off.
    - When you earnestly believe you can compensate for lack of skill by doubling your effort, there's no end to what you can't do

  13. #13
    Quote Originally Posted by Alan Lightstone View Post
    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.

  14. #14
    Join Date
    Jan 2010
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    Tampa Bay, FL
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    2,339
    Quote Originally Posted by Malcolm McLeod View Post
    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.
    - I have enough frequent flyer miles to orbit the sun. Sigh...
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off.
    - When you earnestly believe you can compensate for lack of skill by doubling your effort, there's no end to what you can't do

  15. #15
    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.

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