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I made a router table top out of two 3/4" plies of MDF with formica on both top and bottom. I need to drill a 2" hole in it. Will a saw edge forstner bit work without chipping either surface? Or should I rout it with a circle template? Or something else? Please let me know. Thanks.
I'd drill a small pilot hole first all the way through, with light pressure as it exits the back side. Then use a hole saw, going half way through from each side, and maybe starting off each side with the holesaw running in reverse to score the formica. (Unless you use a drill press, then no reverse:D )
Using the router would be good also, but again, drill your pilot hole all the way through, as mentioned above for your pivot pin, and cut the hole half way through, agiain, from each side. Jim.
Jim-- So you prefer a hole saw to a saw-toothed forstner bit?
I'd go half way thru from each side. With the saw forstner bit, as with a hole saw, run it in reverse to score the laminate, then run it in the forward direction after you are cut thru the laminate. I'd recommend using a hole saw instead. It will be easier to line up both cuts.
It's just that with the Forstner bit, you don't have a good way to follow a pilot hole to be able to drill from both sides. I'm afraid it would be difficult (impossible for me!:D ) to mate up well. In fact, in drilling the small, say 1/8" pilot hole first, I'd then drill out to the size of the hole saw pilot bit, again from both sides meeting in the middle and then running the bit all the way through to insure a smooth bore, then drill from each side with the hole saw. I think this will insure that you have little or no chipping of the formica edge. Jim.
It kinda depends on how clean you want the hole. The method which would produce the cleanest hole would be a plnge router, a template guide, and a circle template. The fastest would be a holesaw.
Why don't you try drilling a test hole in a piece of left over formica on a backup board. If the forstner doesn't chip it, then you should be ok on the actual work.
As to the back side, ifyou use a backup board, you should get minimal chipout (you can test that on a scrap too), which on the underside of the table would never be seen. If you are of the "I will know it is there" mentality (nothing wrong with that), then drill from both sides as others have suggested. Even using a forstner, you can stop when the center point just pierces the formica on the bottom, and finish drilling from the bottom.
Terry