flattening MDF prior to laminate

[tony mashadi]

Hello. Apologies in advance if it seems like a stupid question but here it goes.
I built a new extension table for my cabinet saw using mdf for top on oak frame. After it was done I put on my straightedge and noticed a bit more than 1/32" of raised area in the center. I know that sanding or planing will ruin the smooth surface on MDF but since I want to laminate the top (formica) Im not too worried about fuzzy surface. So is there a way to flatten the top?
- Also can previously sealed MDF (with poly, etc.) be laminated?
-what do you recommend for sealing MDF?
-Finally, I screwed and glued the frame to MDF from under in order to keep the top without holes but since screws catch hardwood much better, could I screw from the top and fill the countersunk screw holes smooth before applying formica and if so what do you use as filler ( bondo?) ?
Thank you

[Jak Kelly]

Personally, I don't think your 1/32" is going to make a difference, but, no harm in sanding it down to perfection, especially since you intend on putting formica over it. I'd just counter sink the holes if wanting to screw from the top, throw a little extra glue over the tops of the screw holes when you adhere your laminate down.

[Bill McNiel]

IMHO 1/32" in a table extension is not worth worrying about.

Poly is fine to seal the surface. Any left over finish will do it.

don't worry about filling the screw holes, the P-Lam will bridge it easily

[Chris Padilla]

If it really bothers you, put a paint stick (or something of 1/16" to 1/8" thickness) in the middle of the panel and clamp it on either end to oppose the curve and leave it alone for a day or two and then come back and see if it is better and more to your liking. Frankly, like the others, 1/32" is no big deal and could be from high humidity (or low) that day.

[Justin Ludwig]

Worried about 1/32 in an outfeed table? You'd crap your pants if you saw the crown in my outfeed table. Mine is about 3/8" in the center to the edge. I've found it rather useful when making long rips as the plies don't suck to it. So I never built a new one. 1/32... pfft.

[tony mashadi]

Thank you all for the replies. The only reason I was stressing over it was because I have the incra fence that rides a bit above the table and I thought it could catch in the high spot. Many good advices in here though.

[Justin Ludwig]

I totally misread your initial thread then. Extension to the right, not an outfeed table. Doh! I still wouldn't worry about it. My extension table has seen better days.

Create a the clearance height for your incra fence based on the crowned spot and you won't have any problems with it sliding right over it. Only problem I could foresee is IF you decided to rip some 10mil veneer against the fence, but I wouldn't advise that to begin with.

[Alan Lightstone]

I found that mine would sag over time (also an Incra router fence), so I screwed angle iron onto the bottom of it. Been great since.

That being said, 1/32" pffft!!!

[Myk Rian]

It takes 2 layers to get MDF flat. Glue them together with the convex sides together, like this )(. They cancel each other out for a flat surface.