Cutting a Slab for a Workbench Top

Depending on the situation, I'll use either a circular saw or a router to make the cut. To be honest, my circular saw and I have never gotten along all that well when doing finish work. The saw does a good job when rough cutting plywood and chopping 2x4's. But any time I try to make a straight cut in something thick, like Maple, I'm not happy with the result.

Even with a carbide-tipped saw blade, the cut can make rough heavy saw marks and burns. And often the exposed shoulder isn't a nice clean, straight line. So here are some ideas for avoiding the problems I've encountered.

If you glued up a slab a foot or so longer than necessary, you will have some extra material to *try* using a portable circular saw to see if you can get a straight, smooth cut. (A little experience can be very helpful.)

But whether this is a test cut or the final cut, first position the slab so the good surface of the slab (the top) faces down. This minimizes chipout on the good side since a circular saw cuts up from the bottom. Now clamp a fence on the slab (at 90 degrees to the edges) for the shoe of the saw to run along. Set up the cut so the heaviest part of the saw (the motor) is over the workpiece rather than the waste. This will help keep the saw stable. And to prevent chipout at the end of the cut, clamp a piece of scrap wood to the far edge of the slab.

When making the cut, think about pushing the saw all the way through. Don't slow down or the cut will burn and create heavy swirl marks. The idea is to keep feeding the saw as fast as it will cut without bogging down.

Another option: cut it to length using a hand-held router and a straight bit. It's a little more time consuming than using a circular saw, but will give a smooth end with a clean shoulder.

Note: As a third option, you can cut the slab slightly (1/8") oversize first with a circular saw, and then use this technique to come back and trim it with a router.

To make the cut with the router, start by laying out a cut line and a fence line. (The distance between the cut line and the fence line is the equal to the distance from the outside of the bit to the outside of the router base plate.)

After marking the cut line, lay out the fence line parallel to it. Then use a square to scribe the fence line around the slab -- so it's on both the top and bottom surfaces. (You need to scribe the fence line on both sides of the slab because you'll start the cut on one side and finish it on the other side.)

Next, to prevent chipout at the end of the cut, score the cut line on the edges of the slab, or clamp pieces of scrap to the edges.

To make the cut, mount a straight bit in your router. In this situation, bigger is better. If you have a 1/2" diameter shank straight bit, use it -- the bit will vibrate less and give you a cleaner more controlled cut.

Then clamp a straight edge or fence along the fence line. Now, holding the router base plate against the straight edge, make a series of passes all the way across one side. Cut a 1/4" or so deeper with each pass, until you're a little more than half way through the thickness of the slab.

Now flip the slab over, carefully clamp your straight edge or fence to the fence line on the other side of the slab and start routing. Make a series of progressively deeper passes until the waste end falls away.