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The hollow square mortise chisel

The hollow square mortise chisel is used in a drill press attachment or mortising
machine, similar to a drill press in many respects, combines the cutting of a four-sided
chisel with the action of a drill bit in the centre. The bit clears out most of
the material to be removed, and the chisel ensures the edges are straight and clean.
This device was invented in 1874 by Robert and Ralph Greenlee.

Square chisel mortising bits can also be fitted to normal drill presses using
a mortising attachment as shown on the left.

[Click here to view] – Available from
Tork Craft.

The
chisel kit is made from a square, four sided chisel with an auger bit inside.  The
auger bit is sized perfectly to fit inside the four sided chisel.  The machine
spins the auger bit removing a circular column of material and the chisel comes
up behind it to square away the rounded edges. The way the chisel works is through
downward pressure by the user. The harder the wood, the more difficult it is to
plunge down.  At the end of the process you get a really clean mortise.

Mortise and Tenon joints are strong and reliable joints. This joint can be seen
in timeless furniture pieces and is testimony to its long-lasting capabilities.
This joint gives support from all sides and has a large amount of glue surface.

When working on a project that calls for multiple mortise and tenon joints, hand-cutting
them all would involve tedious hard labour, resulting with inconsistent joints.
In a situation when you need to produce multiple mortises, there is no better option
than a hollow-chisel mortiser.

video

YouTube
Assembly demonstration of the hollow square mortise chisel