It may make more sense to make an entirely new assembly table, given my desires.
It has to be rollable, as I use it to feed large layups into my vacuum bag, support long table saw sled stock, et cetera.
The concrete floor is very smooth, but likely is not perfectly flat.
The top has to be strong enough for firmly clamping pieces to it anywhere as needed., and about 35″ off the floor.
The overall top should be close to 4′ x 8′, with the supporting rails inset perhaps 5-6″ all around. A lower shelf close to the floor is essential.
Short of welding up a table out of heavy iron, I don’t think any design will be so stiff that it won’t follow slight undulations in the floor height. Therefore I’d like to top to be floating in a sense, but be able to move the table by pushing sideways on the top..
I’m considering a pair of 2×4 platforms 3′ x 6′, with three additional on edge cross rails between the 6′ sides. One such platform would be the lower shelf, the other supporting the top. Legs would be double 2×4’s bolted to the inside corners of the platforms. Casters would be screwed to the bottoms of the legs. Top would be two layers of 3/4″ MDF glued together and ideally covered on all surfaces with white laminate. (The current top has a bow, though, and I’m wondering if laminate may have contributed to the bow.) A 1/2″ dowel at each end would join upper platform and top, like on many workbenches.
Anyone have experience with rolling assembly table, trying to keep top extremely flat? Any better designs for the table? If 1.5″ MDF thickness not stiff enough, I could always glue up a top using 2×4’s on edge after they’ve dried out in the workshop. But then I wouldn’t have the nice white surface.
Thanks in advance for your input.
Replies
stiff vs. floppy table
I think I'd lean toward a torsion-box design supported on a very rigid frame. Then, put height adjustments on the corners, so you can move the table, check flatness with winding sticks, and then adjust individual corners. Naturally, I'll leave it up to you to figure out how to adjust the casters. ;-)
Assembly table on casters
About 15 years ago I built the John Burchette open pedestal table, FWW 109, and needed a large,flat platform for assembly. I made a torsion box from 3 sheets of 1/2" ,good one side, plywood. The web members of the box are 3/4 x 2" high pine and the top and bottom skins are glued and screwed to the web.The third sheet is screwed only to the top sheet and the entire box is wrapped with standard 1 x 4 resulting in a table top 47 1/2 x 97 1/2 x 3 1/2. Initially it sat on a pair of saw horses connected with a couple 2x4"s screwed to the sawhorse legs. After completeing the Burchette table I made a 41 x 91" base from 2x4's, wide side down and used floating tenons to connect the 4 cross members to the long members. The idea was to keep the weight of the entire frame as light as possible without sacrificing structural strength as it was built in a basement shop and I knew I'd be moving from that house. The strength is derived from a diaphram box in the center where 1/4" tempered hard board is glued into grooves in the central 2 x 4 vertical and upper horizontal members. There is also a center web of glued in hardboard parallel to the long side that provides lateral rigidity . To save weight all 8 of the long side verticals are glued and screwed into shallow 1 1/2 x 3 1/2 mortifces that span the base frame connections along the sides. The 4 center verticals are also set in mortises in the cross members, glued and screwed from the bottom. The ends of the frame have pegboard panels floating in grooves in the corner and center verticals. At the top of the frame the vericals are wrapped with 2x4's on edge. Wiring for duplex recepticles in the center of each end and side of the frame is run along the inside of the wrap members. The torsion box rests on but is not fastened to the frame. There are 10 locking casters supporting the entire assembly, There are six drawers and a two door cabinet on each long side. The 3 to 4" of overhang are perfect for clamping.
The design worked; I was able to get this boat out of that basement but it wouldn't fit in the new house. I had to cut it in half, including the center web of the diaphram. I made 2 5/8 x 7 x 1/2" mortices in each member centered on the parting cut and screwed in a plywood filler after each cut to keep the frame intact until all the cuts were made. Then all taken apart, carried each half easily to the new shop and reassembled. The fact that it survived the surgery is testimony to the diaphram construction. I have yet to replace the upper skin but I have refinished it several times. The original construction was not documented but in the first of the attached photos you can see some aspects of the frame as the movers try in vane to get it into the basement. The second shows it reassembled and working just fine in the new shop.
Hope this helps. If you are interested in more detail, send me a PM with your e-mail address and I'll be glad to share.
Regis
Simply build a rigid torsion-box top that will stay flat no matter how it's supported. Then a reasonably sturdy leg system with large casters. Given that you've got a relatively smooth and flat floor, this will be perfectly acceptable. I use an old hospital gurney for a rolling assembly table. The height adjustment is a huge attribute when using it in conjunction with my vac press bag. I can load 4x8 panels by myself with no problem.
Adjustable Assembly Bench
Have you had a look at the" Noden Adjustable Bench hardware." Look it up on the internet. I'm leaning toward this to build a combination work bench and adjustable assembly table so I can save space by not having to build one of each.
You may be interested in the Norm Abrams assembly table --- torsion box design on casters which lift to allow it to stand on its four legs. i built one, and it's very sturdy and useful. A removable, sacrificial layer of hardboard/MDF/ whatever is also part of his design. (See the New Yankee Workshop web site for details.)
Assembly table
No one has mentioned the casters. I would recommend 5" poly wheels. I got mine from Rockler.
It is up to you whether you want 4 swivel - or two swivel and two fixed. Their are advantages to both approaches.
Frosty
We're lucky enough in Cincinnati to have a company that builds casters from the standard parts. So they can combine any type of wheel with any type of bracket with any type of brake, . . . And of course when a wheel fails (they don't last forever) I can get a new wheel installed on the same bracket and brake.
For the top I decided to make a rather thick torsion box using MDF as demonstrated on a video from Wood Whisperer, who said he was copying from David Marks. I'm building the apron on the completed torsion box, so it will be very flat, and will then install the apron on the leg assembly. The top still will float on the apron, kept in place with some blocks at the inside corners of the apron rails screwed to the underside of the top.
Work table
Sounds like youve got a plan - a good one. Go for it.
Lucky you on the casters.
Frosty
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