Mortising Chisels: Drilling a Square Hole

Previously, we have discussed the various forms of joinery and one such form of joinery we spoke about was the Mortise and Tenon. This method of joinery requires one to essentially create a rectangular crater into the piece of wood at a 90-degree angle and various lengths depending on the requirements of the project. Traditionally, these mortises required the chisel skills of a seasoned woodworker to perfect. As you can imagine, this can often be a very time consuming and elbow-grease intensive task.

Enter the mortising chisel.

Invented in 1874 by Robert and Ralph Greenlee of the Greenlee Company, this bit is made of a four-sided square chisel with a drill bit in the middle, this bit is then fitted onto a bench-mortiser. This specialized mortise and tenon drill bits can dig and remove material whilst still ensuring that the edges are clean and perfectly straight.

With this drill bit attached to a bench mortiser, these joints can be achieved to perfection. These machines are perfect for this application and can be found in many professional workshops where these joints are made often and therefore efficiency is key.

No bench mortiser? No problem

For the home woodworker, however, acquiring such a machine could simply be an unjustified additional expense. One then has the option of achieving the same task with the use of a router, a well-constructed jig and a straight router bit. However, often the creation of the “perfect jig” can be complex and time-consuming. Moreover, hand-holding a heavy plunge router over a small piece of wood over-and-over again can be very laborious and inefficient.

Now, of course, one could mark and measure the required rectangular mortise, grab the appropriately sized bit and simply turn the drill press on driving the wood freely through the spinning chisel. This, however, adds a lot of stress on your drill as well as on your workpiece. This approach also lessens your chance of a straight and clean cut which essentially defeats the point of using these mortising chisel bits. This is why the use of a mortising attachment is essential.

The mortising attachment is fitted onto the drill press to ensure that the mortising chisel bit is secured and that the workpiece passes through the bit in a straight fashion. These are the elements which are most important in guaranteeing a perfect fit. Find out more about how to use a mortising chisel attachment here: TorkCraft Hollow Square Mortice Chisel Attachment

Square Mortising on Doors

There is another instance in which one would want to drill a square hole, and this would be to drill a crater to fit something other than another piece of wood inside. Something like a door lock. There are currently quite a few lock mortising attachments available on the market for these door locks, the best and most well-documented of these is the Souber Tools DBB Lock Mortiser. You can find out more about this hand-held drill jig here: Souber Tools DBB Lock Mortiser