Cutting Large Slots
in Woodworking
In the past when I've worked
on a project that required a large slot, such as a hand hole, I drilled out the
two end holes, then used a jigsaw to remove the waste in between the holes. It
worked okay, but sometimes the sides of the slot didn't end up straight and smooth.
So when I built a wooden case
for my sharpening supplies recently, I tried a couple of other techniques that
gave me much better results.
My approach to cutting the slots
started out the same as my old technique. After marking out the shape of the slot,
I drilled the two end holes on my drill press. A simple fence helped me keep the
holes lined up. But from that point on, I did things differently.
Instead of cutting out the waste
with a jigsaw, I switched to a bit that was slightly smaller in diameter than
the one I used for the end holes. Then I drilled a series of overlapping holes
the length of the slot. I used a Forstner bit because it doesn't chatter like
a spade bit will. If you use a spade bit, keep the speed slow and don't overlap
the holes as much -- this leaves more stock for the pilot point to bore through.
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 Once I had the slots drilled out
in the two end pieces, all that was left were scallops of waste along both sides
of the slots. On the first piece, I used a chisel to pare away the waste stock.
Using the widest chisel I have (1"), I kept the flat side toward the marked side
of the slot. You want to hold the chisel vertically so the slot sides remain perpendicular
to the face of the workpiece. Then just slice away the scallops to sneak up on
the side marks. Also, take some extra care near the ends so the slot sides blend
smoothly into the end holes.
Even with some careful chisel
work, the sides of the slot still needed a little sanding to smooth them up. And
while the results were much better than my jigsaw effort, I decided to try something
else. It wound up being the best solution yet.
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 Using some double-faced carpet tape,
I attached a couple of straight-edged pieces of scrap to the workpiece as guides.
You want to get the straight edges of the scrap lined up perfectly with the marked
sides of the slot. Next, I installed a flush-trim router bit in my table-mounted
router, and raised the bit up so the pilot bearing would ride against the guide
boards. Then I positioned the workpiece over the bit and trimmed the sides smooth.
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| It may take a
little more setup time than grabbing a chisel, but the flush-trim bit makes quick
work of trimming out the waste and leaves the slot sides perfectly smooth. Just
make sure you stop routing when you get to the edge of the end holes. |
