From DT Online
Revision as of 10:20, 8 February 2016 by DT Online (Corrected Link)
The square chisels used are sharpened square tubes inside which an Auger Bit revolves to remove the bulk of the waste as the chisel is pressed into the workpiece. Although this can be quite slow for production work, the hollow chisel is easy to change when different size mortises are needed making them ideal for small scale furniture production.
A Mortising Attachment can usually be fitted to a Drill Press and for occasional use by an individual, this avoids the cost of an additional machine. The cutting tool (i.e. the Auger Bit) is almost completely enclosed within the hollow chisel making them relatively safe to use.
An alternative for heavier work is a Chain Mortiser but the mortise they cut can have rough edges where the chain exits the mortise so they are not suitable for fine furniture making. They are similar in operation to a Chain Saw and not recommended for use in schools.