What is a mortiser? If you are not into woodworking, chances are that you don’t know what a mortiser is. Most woodworking tools are well known but the mortiser is an exception. The mortiser is a very useful tool, if you are going to cut rectangular or square holes in wood. Otherwise it is difficult to justify the purchase.
The mortiser was invented back in 1874 in Rockford, Illinois, by Robert and Ralph Greenlee. Their company, Greenlee, is still producing mortisers today. In woodworking, it is very good to be able to quickly create square and rectangular holes. Mortise and tenon joints has been around for ages. But it requires that you can create accurate mortises. This had been done manually with the help of a chisel and mallet for thousands of years. But it was very time-consuming. The Greenlees managed to solve this by creating a machine that could create mortises.
A mortise is cavity cut into wood, while the tenon is a piece at the end of a piece of wood that is going to be inserted into the mortise. The mortise and tenon joint was used already in the ship found at the Giza Pyramid, which was probably created around 2,500 BC.
The early mortisers were what today is called a square chisel mortiser. It has many similarities with a drill press. It has a drill bit that cuts the hole and a hollow rectangular chisel that makes sure that the edges are straight and clean.
Nowadays, you have two other types of mortisers as well. The chain mortiser is meant for cutting large mortises. They are expensive and aimed at the timber and log home industries. The horizontal mortiser is simply a router that has been mounted sideways. It is very good for floating tenons. If you have a router, you can create your own horizontal mortiser simply by building a stand and router mount.
The mortiser is often found in professional workshops, it is the best tool for cutting mortises. But most woodworking amateurs don’t need a mortise very often which makes it difficult to justify the expense. If you have a drill press, you can buy a mortising attachment. They are relatively cheap but unfortunately they are not very good. They are awkward to use and the result is not very good, often you need to manually improve the mortise afterwards. Another possibility is to use a router but that takes a lot of time and you still need to use a chisel and mallet afterwards, the corners are unlike to be square. So if you are regularly cutting mortises, investing in a mortiser is likely to be a sound decision.