Flush trimming large sheets

[Prashun Patel]

I have a few sheets of 2x8 sheets of 3/4" mdf that I need to laminate for a benchtop. What is the best way to end up with a perfect, flush-edged top?

The easiest and safest seems to glue/screw up all 3 sheets and then use a circ saw to flush everything.

Is there an easier or more accurate way? Tablesaw?

[Jerome Hanby]

If you had a pattern bit long enough, some kind of clamp on straight edge and a router would do a smooth job.

[Narayan Nayar]

Assuming like blades, a circular saw with a guide and a tablesaw are essentially the same thing. If you have a plunging circular saw, that might be slightly better, since you'll be cutting through 2.25" of material and you could take multiple passes without burning anything. MDF is pretty easy to cut though.

The one thing I'd say is that 3 laminated 2x8 sheets of MDF will be pretty heavy. If you've got help or appropriate work support or both, you could do it on a decent tablesaw in one pass. But I speak as someone with a bad back, so maybe I'm more careful than you'd have to be.

The other option of course, is to just cut each sheet to size then follow up with a long flush trim bit and a router.

[harry strasil]

When I jointed the planks for my workbench, 1 3/4 Pin oak, I used my Aluminum straight edge and a router with a top bearing pattern bit and then flipped them over and used a bottom bearing bit to finish. My planks were rough sawn and each had a slight amount of taper in width. I ended up with perfectly jointed edges and the planks were all a consistant width the whole length, I didn't think I could joint them on my old 6 inch sears jointer and I was using my table saw for a table and besides I didn't have enough room at the end of my shopmade table saw to true them up with the table saw. Disadvantages of a small shop space. I also used the clear whirlwind under router dust port and had very little swarf to clean up.

[Robert Reece]

I will cut one sheet exactly the way I want it, then overcut the others by a 1/4" or so. During glue up just make sure the oversize sheets overhang the "template", then clean up the overhanging one with a router. Hopefully you can do this outside with a stiff breeze blowing.
MDF should be 49x97 so overcutting shouldn't be a problem.

[Phil Phelps]

Cut one the size you want and laminate the other two top and bottom. Now you have a sandwich with the center MDF as a guide. Flush trim with a router. I'd make the top and bottom no more than 3/32's over.