A mortiser is a woodworking tool used to cut square holes in a piece of wood into which a similar-sized tenon is fitted. These are common in joinery, and also occur in building construction.
There are several types of mortisers, each designed to suit the particular type of hole it’s cutting. They range from the simple chain mortiser (which can be retrofitted to a drill press) through to an all-in-one machine like the RIKON Mortiser with Dual Axis Table.
Chisel and auger
Mortising is a strong and reliable joint that is common in many old pieces of furniture. However, hand-cutting a mortise and tenon can be time-consuming and hard work.
Modern mortising machines have a specialized cutting system that uses a hollow square chisel with an auger bit inside it. The auger bit removes the majority of waste timber as it rotates, whilst the chisel squares up the holes created by the auger.
To get the best results from a mortiser, it is important to set the hollow chisel and auger correctly. First, slacken the chisel locking screw slightly and push it against the machine shaft, so that there is a small clearance between the chisel and the auger bit. This is a crucial step, as the chisel will then be able to clear its chips up from the auger bits, allowing the machine to cut.
Chisel and fence
When mortising, it’s important to have your chisel and fence set up properly. This ensures accurate cuts and a solid connection between the chisel and the fence.
To get your chisel and fence aligned, it’s best to use a long reference surface that is square to both the outward and inward faces of the chisel. For example, a steel 6″ rule is a great option.
Another good idea is to use a rare-earth magnet. The magnet’s magnetic field is strong enough to hold the chisel in place against the fence, making it easier to align the chisel and fence.
Once you have your chisel and fence positioned, it’s time to plunge the chisel into the wood. Make a series of shallow cuts, giving the chisel plenty of time to cool down and clear any chips out of the ejection slot in the back of the chisel.
The last thing you want is tearout, where the chisel cuts into the opposite edge of the hole (Photo 2). It’s easy to create this problem when chopping through mortises.
Chisel and chuck
A chisel and a chuck are essential components in mortising. They are used to cut mortises, which form the half of the joint where a tenon is formed.
It’s important to keep the chisel sharp when cutting these joints. Dull chisels will heat up and damage the bits or corrode the workpiece.
To avoid this, you should lubricate the chisels with a non-staining lubricant before use. It’s also best to lubricate the center bit, as this prevents heat damage.
In addition, you should square the mortise bit chisel to the fence of the mortiser before cutting. This ensures that the mortise turns out evenly and accurately.
Another handy accessory is a hold-down that attaches to the top of your rip fence to keep your workpiece from lifting off the table surface as you retract the chisel. This saves you time and reduces vibration.
Chisel and bit holder
A chisel and bit holder is an important tool when mortising with a hollow chisel mortiser (HCM). It allows you to hold the chisel and chuck at the proper height while drilling. The holder will also prevent your chisel and bit from falling out of the chuck when you’re finished.
The chisel and bit holder should be properly set up before you start using the HCM. It should be squared to the fence of the mortiser so it will make a straight cut when you’re done.
Depending on the type of mortiser you have, you might need a variety of bits to fit into your chisel and bit holder. The best option is to simply check your mortiser’s owner’s manual to see what types of bits are compatible with it.
If you’re working with a chisel and bit holder, it’s important to use good quality chisels and bits. If you don’t, it can ruin your machine and its performance.
