Dado before laminate or after?

[Muttley000]

I am making an outfeed table that will be covered with black Formica.  I’ve done very little Formica work in the past outside covering rectangles and trimming flush.  Should I put the clearance in for the miter slots before laminating, and then use a trim router to re-expose them, or should I just put them in after the fact?  I am wondering if the laminate will crack up and possibly chip out where it is unsupported if I put the dadoes on first.

 

[Packard]

I’ve put in dadoes on melamine clad sheets by just cutting the dado. The melamine clad sheets stand up pretty well and represent a significant time and cost savings. 

My outfeed table is MDF and I applied a few coats of wipe on poly.  I can’t tell you how many coats, because each time I apply a wipe on finish, I take the mostly used rag and wipe the rest onto the table top.  I suppose it is not an entirely even coat, but it adds lubricity to the surface and looks fine. 

I did the same with my radial arm saw table top.  It ads no cost, and no setup and takes just a minute or two and reduces my waste.  Very efficient.  (And I am not usually very efficient,)

 

[Crazyraceguy]

Most of it depends on the depth of the dado itself. I have done it both ways and generally prefer to cut the dado first, laminate over it and then trim it back. The only really good reason not to do it this way is if the dado is too shallow. You have to have enough bearing surface on the sides for the bit to cut, yet still ride the side.
I would rather do the dado first for two good reasons. First is simply as insurance against screw-ups.  If there is a problem with cutting the dado (router moving away from straight edge, board moving from fence, etc.) you can still fix it. Fill the cut and re-cut it. The other is chipping. If you cut the dado with a table saw, there is a very real possibility of chipping the laminate. If it is done after, no problem. Doing the dado with a router can do this too. Down spiral bits are far better for this, but they are notoriously hard to use in this type of cut. The cut gets bound up with debris, because of the cutting action.
If you do the dado first, do yourself a favor and cut a filler piece for the dado while you apply the contact cement, especially if spraying. It will be a lot easier to not have glue overspray in the groove while routing the laminate away later.