The bit bores a round hole using an electric motor and the square chisel
cuts the four sides by using downward force using lever action. On a drill
press the downward lever is short and the pressure on the square chisels is
On a dedicated mortiser the square chisel is driven downward with a much
longer lever arm mounted on a much larger rack and pinion.
So when you lower the lever down while boring the round hole the square
chisel cut effectively and smoothly.
Works OK for me. I also have the Delta mortising attachment. It does
what it says. I would bet a dedicated mortiser would make a cleaner
hole, but who cares? You can't see it anyway.
For the weekend hobbiest, I think it fits the bill.
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