Laminate on saw extension table

[Mark D Hillier]

I'm rebuilding my extension table to support an over-arm blade guard/dust collector and I want to put a formica top on it to make it durable.

The table itself will be a torsion box design and will be pretty beefy.

However, when I built my router table, I laminated the top (1.5" worth of Birch plys) and the darned thing bowed from the laminate.

I'd like to save the time and expense of laminating both the top and bottom of this extension table but I'm nervous that it could possbily bow again.

With a torsion box design, am I being over dramatic ?

Looking for opinions !

[Tom Veatch]

In my shop I have a TS outfeed table (3/4" ply), a TS extension table (3/4" MDF), a router table (double 3/4" MDF laminate), a roll-around shop table (3/4" MDF), and an assembly table (4" thick MDF torsion box - 1/2" MDF skins, 1/2" MDF grid 7" o.c.). All of them are laminated on one side with a Formica type laminate using solvent based contact cement, and I've noticed no bowing in any of them.

Don't know what I did differently from you, but based on my personal experience, I have absolutely no hesitation about laminating any future projects in like manner.

[Jim Andrew]

When I built my first router table, I put laminate on it, just on the top side, and of course it did not stay flat. So on my new one, I just built the top of hardwood, and put finish on both sides, so it is sealed all surfaces. Think if you were to seal the bottom and edges it would probably stay flat. Jim

[Jim O'Dell]

I have two 15" X 120" torsion box tops for my multifunction wall cabinets that have laminate on the visible surfaces, and sealed with 3 coats of water based poly on the bottom and back edge. Same for my torsion box extension table, except I believe I laminated all but the bottom. I haven't noticed any appreciable warpage. The two long tops have been that way for about2 years.
But the common rule to torsion boxes is to have the same finish on all sides, as well as the same material top and bottom. Jim.

[Mark D Hillier]

Hmmm...I wonder then if the key was that I never sealed the other surfaces then.

I guess there is only one way to find out !

[Tony Bilello]

You can get a product made by Formica and all of the other laminate manufacturers called a "backing sheet". It is the same material as the backing for the plastic laminate. It is obviously much cheaper because there is no plastic. My point being that this is the acceptable backing for the bottom side of your table, torsion box etc. There is no need for the plastic laminate to be on the bottom, just the backing sheet. Painting with urethane or most other products are not as good as a backing sheet but way beter than nothing at all. Moisture will eventually penetrate the urethane but not the backing sheet.
Some climates are more conducive to this curling up of the tops than others. It depends on humidity levels. It might be a good idea if your profile indicated your rough geographical area for future reference. These kinds of problems are less dramatic in dry climates like Ks, Az, N.M. etc.

[Todd Burch]

For my TS outfeed table, I built a 2X4 frame and used a 3' x 6' piece of white melamine. It has worked well for many years.

I also have (had) a large Record vise mounted to the backside of it (opposite side of where you stand to run the TS). However, recently I was using the vise as an aid to remove the upper control arm shaft from the upper control arm of a front end suspension, and broke the vise off. Part of the melamine top came with it, so after 10+ years of service, it's time for a new piece of a melamine - which, is fine, because the old one was getting pretty shabby looking with stains and normal wear and tear.

It never bowed, as the melamine covers both sides. I did wrap the edges in t-mold and radiused the corners. It's slick too, which is a nice feature.

Todd

[Dell Moore]

Didn't Fine Woodworking do an article about "Phenolic" (SP?) plywood that would be perfect for this sort of thing? Of course I don't know if the price of this stuff is prohibitive or not. I do remember that I thought of getting a sheet for the very purpose of an outfeed table, but then I moved and it all got put on the back burner.

Has anyone used phenolic ply?

DEll

[John Callahan]

.................. +1 for backing sheet per Tony B.

[Chip Lindley]

Mark, (IMO), the warpage issue stems from the use of water-based contact adhesive! I swear by the *deadly, old-fashioned* solvent-based contact cement! ANYTHING *water* will induce warpage in wood when applied to only one side!
That being said, (IMO) IF a tortion box warps, it is NOT the fault of any adhesive applied!

After my first BAD experience with water-based contact cement in the 80s, I won't go back! The stuff would not bond in the 50-60 degree temp of my home under construction! I had to IRON all my almond door panels to achieve adhesion! NOT a problem with solvent-based contact cement!

[David DeCristoforo]

You are "comparing apples and oranges". On the one hand you have a "solid" top made up of laminations. On the other, a torsion box. There is no way they are going to react the same way to anything. It is unlikely that the torsion box would warp and it is perfectly understandable why the "solid" top did. Nevertheless, if it was me, I would "suck up" the time and expense and at least apply a cabinet backer to the underside.

[Mark D Hillier]

You can get a product made by Formica and all of the other laminate manufacturers called a "backing sheet". It is the same material as the backing for the plastic laminate. It is obviously much cheaper because there is no plastic. My point being that this is the acceptable backing for the bottom side of your table, torsion box etc. There is no need for the plastic laminate to be on the bottom, just the backing sheet. Painting with urethane or most other products are not as good as a backing sheet but way beter than nothing at all. Moisture will eventually penetrate the urethane but not the backing sheet.
Some climates are more conducive to this curling up of the tops than others. It depends on humidity levels. It might be a good idea if your profile indicated your rough geographical area for future reference. These kinds of problems are less dramatic in dry climates like Ks, Az, N.M. etc.

Tony,

I'm in Calgary, Canada -definately dry here. (I updated my profile with that tidbit, too).

Backing sheet is new to me -I'll check at my local building centre and see if they have it.

TNX

[Larry Prince]

Tony,

I'm in Calgary, Canada -definately dry here. (I updated my profile with that tidbit, too).

Backing sheet is new to me -I'll check at my local building centre and see if they have it.

TNX

If you do decide to use the backing, be aware that this stuff is incredibly thin and brittle. It has to be handled with more care than probably anything other material in your shop. This becomes much less a factor once you get it cut into smaller "project size" pieces but, until that time, a 2nd person to help with handling the full 4x8 sheet will be of great benefit.

[ken gibbs]

Wwhy don't you reinforce the botton of your extension?

[Ron Bontz]

Well they call it "balance backer" where I get my wilson art. That's what I use if I don't have extra scrap laminate I can use. I do also use solvent based adhesive. It has held up much better over the years compared to that latex based suedo glue. Once again many different opinions from different angles. Best of luck.:)