How flat is flat for an assembly table?
king_1223
| Posted in General Discussion on
Hello I’m in the current process of building a assembly table with an mdf top. I was planning to just use stretchers to keep the mdf from sagging but I am now contemplating if that will be flat enough. Should build a torsion box table assembly table or take the easier route and build a more basic assembly table?
Replies
I don't kno what to tell you in terms of measurements but, if you use it the way I use mine, I say make it as flat as you are capable of making it. I made mine some years ago out of an old lumber core door and covered it with plastic laminate. I have a long metal straight edge and compared to that the table is pretty flat; not perfect but, any deviations would be measured with feeler gauges. I frequently clamp projects down to mine while the glue dries to make sure they are sufficiently flat and square.
I think 3/4" MDF should make a fine smooth top. However, you will need to make sure the rest of the table is rigid enough that any unevenness in the floor does not telegraph through the structure and distort the top. Also, make sure that the supporting stretchers are jointed straight and perfectly aligned with one another. Doing that, I don't think you need a torsion box but, that is certainly a good option. I like my plastic laminate top surface but, there are other options like hardboard. One other suggestion: make your top with a substantial overhang (maybe 4-6") because you will probably want to clamp stuff to the table from time to time.
A torsion box is the way to go.
Make the inner and outer from 18mm MDF.
https://thewoodwhisperer.com/videos/episode-18-assembly-table-torsion-box/
Absolute flatness is not essential - you'll not be taking engineering level dimensions off it after all, but it does need to be close. 1mm over 2M is easily achievable and with care and a little luck you can do even better.
Another vote for torsion box. The Paulk bench is very popular, a version of a torsion box.
You have to start out with a flat, planar surface to build on. Marc Spagnolo and has a good video on how to dot his with sawhorses and shims.
Torsion Box without a doubt just make sure you build on a flat surface, level is irrelevant but flat is not.
I made mine by screwing 3/4" HDF (high density vs. medium density fiber board) to a 3/4" piece of plywood. I put a screw every 6 inches and had to plan a little so I could route track into the top for clamping. It's heavy, very heavy, but after 6 years its still flat. It's also solid to work on and I do have an overhang so I can clamp.
I did not build a torsion box. But that would definitely work.
If it's just an assembly table don't pull your hair out over flatness. If the parts fit together they way they were planned you could assemble a project on the floor.
Just for shits 'n giggles, my build table is a 1970s kitchen tabletop with the formica removed with a bulky custom base.
Mikaol
If it is just assembly, I would buy the widest hollow core luan door and make a base for it, or use 3 saw horses. It will be plenty flat enough, cheap, and fast.
Mine is two layers of 3/4" MDF plus one top sheet of black phenolic film faced 3/4" plywood. Heavy, but it's on 6" casters a and has excellent balance of stability and mobility. Dead flat. I bored a grid of 3/4" dog holes with a Whiteside carbide upcut bit and finished the holes through the top with a Wood Owl auger bit. The phenolic laminated plywood is sold for use in concrete forms. The MDF sheets are laminated with Titebond and the phenolic plywood is held down by countersunk screws, so that top sheet can be replaced if damaged.
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