Mortisers for Woodworkers

In the next part of his beginners’ guide, Peter Bishop discusses the topic of mortisers as well as offering his advice and tips on setting them up and getting the best from this handy machine.

The black art of the mortise has been greatly helped along by the availability and profusion of mortising machines. There’s really nothing new about this – they have been around for years. However, they are more affordable these days, probably because most are made overseas. Cheaper they may be but they should still be engineered to give you a well cut joint.

Mortise cutting heads

Generally speaking, there are four main types of mortise cutting heads.

• For industrial, mass-production of mortise joints machines with single or multiple oscillating heads are available. Having set the predetermined location of the mortise or mortises the central cutting tool oscillates from one side to the other, cutting as it advances while two straight cutters trim the ends of the holes. The cut is usually made in a horizontal direction, but not always. Very expensive, very efficient, but probably not one for us!

• Similarly, the chain cutting mortise head is more of a production machine. A bar is mounted with a chain upon which are located some cutting teeth, operating in a similar way to a chainsaw. Usually a single-head, the machine can cut vertical mortise joints quickly and efficiently but is a bit brutal for fine work.

• The hollow chisel cut is the most popular for flexibility and ease of change over. A simple, square chisel with a central auger to remove the waste, these machines are predominantly vertical cutting. This is the one we’ll concentrate on in this article.

• The slot mortise cutting head is often found on combination machines and a simple cutter is mounted in a chuck. The work is presented to it and a hole bored to a predetermined depth and, if the cutter is capable, the component is then passed by the cutter, which slices out the mortise slot. For deep cuts a number of passes must be made to avoid breakage. As an attachment these tend to cut horizontally.