The square chisel mortiser (also called hollow chisel mortiser), 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 center. 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 (founders of the Greenlee Company). We love our Mafell mortiser. We use it to cut all our mortises. We do a lot of oak timbers and we use this machine every day. Very light and stable. If we ever need another one, it will be a Mafell again."

I have never used a Mafell, and could have gone with one but I had read that the SP had a couple of small advantages over the Mafell. Chip clearing ability being one. Plus the distributer isn’t far from me. When buying a chain mortiser for woodworking, just remember that they come in two different types i.e. portable machines and stationary machines. Depending on your requirement and usage, you can choose the one that fits your needs. Reuleaux triangle on MathWorld - includes an animation of the action of a Harry Watt square drill bitIt’s also quite safe to use, thanks to the safety switch that protects the user. The weight of the machine is, however, a bit more than the Makita as it’s around 55 pounds. The chain is chrome-hardened and does not require lubrication before use. It has a max mortising depth of 5-7/8 inches which is quite large. The mortising handle is long and easy to use, ensuring minimum force is needed to plunge the bit into the work piece. Other tools such as a router could be used for the task, but the router usually requires special attachments, jigs or templates and the router bit leaves rounded corners that might need to be squared by hand with a chisel. Alternatively, the tenon can be rounded with a rasp to achieve an equally strong joint. If you need dedicated workhorse mortiser to produce mortises day in and day out, one of the best units I’ll recommend is this Powermatic 719T.

The bit of the router is aligned with the work piece where the cut is needed, and using a system of levers, the router is moved to and fro through the cut, until the whole slot is complete. For large trusses: horizontal slot mortiser stands are also available enabling depths up to 15-11/16" deep ( SG 400) or 19-5/8" deep ( SG 500) as well as angles up to 45 degrees. Keep running the mortiser in-between plunges and let the machine run for a few seconds after mortising to bring cool air into the motor.

Traditionally, a mortise would be cut by hand, using a chisel and mallet. However, due to the precision of fit required for a mortise and tenon joint, this can be a difficult and time-consuming task. It’s more like a drill press, but instead of a simple drill bit, it makes use of a hollow chisel and bits that allows the user to drill square holes into the work piece. Health & Safety should be assessed on an individual basis. The advice given here should only be used as a guideline. It is the responsibility of the Employer and the Operators to ensure that they are competent and qualified to use the equipment and that they have taken the necessary safety precautions If you have a lot of mortises to cut for a wood workshop, getting a chain mortiser is the way to go. These machines are perfect for use in all types of conditions.