Building a FLAT table that will stay FLAT

[M Toupin]

I'm in the process of building a drum sander. It's about complete with the exception of the table which will be 30" X 40". I need some ideas and advice on building a FLAT table that will stay FLAT. The first attempt was two layers of particleboard laminated with Tightbond III, edge banded with 7/8" oak and topped with high-pressure laminate. Unfortunately it's cupped about 1/8" on both long and short ways… Needless to say, that's unacceptable and now I'm working on version two. I'm not sure exactly what went wrong with the first one, but I think the moisture in the glue might have contributed to my problems along with only putting laminate on the topside.

My new plan is to laminate three sheets of3/4" MDF with high-pressure laminate on both sides and 7/8" oak edge banding. While I think this should work, but I'm still concerned it might not stay flat, especially over time. I'll use epoxy this time around. I'm also considering laminating strips of 1/8" X 3/4" steel flat stock on edge within the layers. My idea is to slot the bottom two layers and put 3 or 4 strips in lengthwise and then slot the top two layers and put 4 or 5 strips in widthwise on that layer. My thinking is that this will provide enough additional stiffness to eliminate any tendency to sag or warp over time.

So my question is does this sound workable? Is the imbedded steel overkill? Will epoxy work better, or is there another adhesive that might work better?

Mike

[Phil Maddox]

Have you thought about torsion box construction? It is easier to maintain flatness this way.

Do you have a maximum thickness that will work with your design? T-B construction is much thicker than laminated construction.

It goes without saying, but you are building this thing on a flat reference table, aren't you.

Good luck - pics please

Phil

[M Toupin]

I guess I should add that the actual unsupported span of the table would be about 30" wide by 24" long. The remainder will be split between the in feed and out feed tables with about 8" overhang front and back. The rear will be hinged and the front will be supported via the twin screw elevation mechanism with each screw placed approximately 1/3 of the width, or about 10" from each edge.



Phil,
I'm a bit thickness constrained now so T/B is not really feasible. And yes, I'm building it on a flat reference surface.

Mike

[M Toupin]

Ok, here's the obligatory pictures. The second is the height adjustment mechanism which is twin screws driven via chain. The sprockets were welded to nuts and a set screw tapped into the side of the nut to allow fine adjustment. This setup allows me to get the screws the same height and provide some adjustment should things get out of whack.

Mike
3282232823

[tod evans]

m, try using angle iron or square tubing...... (gotta fix the 1st name :) ) .02 tod

[Jim Goldrick]

I had the same problem with particleboard when I built by first bench. The second bench I built with blue box birch plywood and ash flooring for the top. So if you really want it flat, I would go with plywood and a wood surface that can be hand planed flat.

HTH

[Brandon Shew]

Have you thought about using apiece of laminate counter top. I've had good lick with that in the past as far as staying true and the laminate should make for a good sliding surface

[David Abel]

I'm in the process of building a drum sander. It's about complete with the exception of the table which will be 30" X 40". I need some ideas and advice on building a FLAT table that will stay FLAT. The first attempt was two layers of particleboard laminated with Tightbond III, edge banded with 7/8" oak and topped with high-pressure laminate. Unfortunately it's cupped about 1/8" on both long and short ways… Needless to say, that's unacceptable and now I'm working on version two. I'm not sure exactly what went wrong with the first one, but I think the moisture in the glue might have contributed to my problems along with only putting laminate on the topside.

My new plan is to laminate three sheets of3/4" MDF with high-pressure laminate on both sides and 7/8" oak edge banding. While I think this should work, but I'm still concerned it might not stay flat, especially over time. I'll use epoxy this time around. I'm also considering laminating strips of 1/8" X 3/4" steel flat stock on edge within the layers. My idea is to slot the bottom two layers and put 3 or 4 strips in lengthwise and then slot the top two layers and put 4 or 5 strips in widthwise on that layer. My thinking is that this will provide enough additional stiffness to eliminate any tendency to sag or warp over time.

So my question is does this sound workable? Is the imbedded steel overkill? Will epoxy work better, or is there another adhesive that might work better?

Mike

You should be fine this time around with the 3 MDF, laminating BOTH sides. plastic resin glue could also be used to bond the MDF (no creep). edgbanding for looks.

Your first time out, you didn't laminate the underside and PB sucks anyway. :)

[Chris Padilla]

Try laminating with 1/2" MDF to get more layers and more glue into the top. I suggest Unibond 800 for this. Also, as suggested, all exposed sides need treated/sealed in some fashion or moisture will get into the MDF (you are in a humid area) and eventually cause some sag. The hardwood edgebanding is great along with a plastic laminant on top but the bottom should also get some plastic laminant.

Finally, that large area should be supported as best you can.

Combine all this and you should have a pretty stable/flat surface for a long, long time.