Mortises are one of the strongest woodworking joints and are a sign of quality whether in fine furniture or timber-frame cabins. A skilled carpenter can make them by hand, but it’s a laborious process. A bench mortiser is a more productive solution, delivering repeatable accuracy in a fraction of the time. We’ve been looking at the latest models to help you decide which to buy, and we’ve made a few recommendations at the end. Our favorite, the Powermatic PM701 Bench Mortiser, is a superb tool with the power and precision to satisfy the most demanding woodworker.
Considerations when choosing mortisers
How a mortiser drills square holes
Most mortisers are much like a heavy-duty drill press, but instead of the standard drill bit, you have a mortising chisel. This has a large auger in the center that turns within a square steel tube. The tube ends are sharp chisels. As you lower the tool into the wood, the auger creates a round hole that removes the majority of the waste. The chisels slice away the edges, so you end up with a square hole. To increase the size of the mortise, you simply make additional square holes alongside the first.
The exception to these is the chain mortiser, which is a lot like a chainsaw mounted on a frame. As the chain rotates it is plunged into the material, gouging out a rectangular hole. It’s specifically designed for log cabin or timber frame building construction.
Choosing the right mortiser
For this article we’re assuming most people want a shop mortiser. There are a number of important considerations.
Floor-standing models are powerful and offer additional benefits like tilting heads and tables so compound angle mortises can be created. However, they’re big, expensive tools seldom found outside large pro shops. Most woodworkers — professionals included — will be fine with a benchtop mortiser.
Budget models can be reasonably light, maybe 40 pounds or so. This makes it possible to move them aside if workshop space is limited. The challenge there is stability in use, which impacts on accuracy. Most mortisers have bolt holes in the base so they can be fixed to the bench, and really they should be. High-end mortisers can be 100 pounds plus.
The difference in weight is usually down to cast iron used in manufacture. This not only adds rigidity, but helps dampen out motor vibration. The mortiser cuts more cleanly as a result. At the very least we like to see a cast iron base. Better quality machines also use cast iron for the column that supports the motor.
Motor power is another priority. Mortising chisels start at 1/4”, and 3/4” versions are not uncommon. You need considerable drive for larger versions to cut effectively, and we would look at 1/2 horsepower motors as a sensible minimum. More is never a bad thing, particularly if you’re working with hardwoods. A long handle is also a benefit, as the increased leverage means you need less physical force. Maximum depth of cutting — technically the spindle travel — is also worth checking.
Workpiece clamping needs to provide a secure hold, but be easy to operate. You seldom create a mortise with one plunge cut, so the ability to move the workpiece left and right to extend the mortise is important. Sliding tables allow this, and on high-end mortisers, control might be made easier by the addition of hand wheels.
You’re unlikely to find a mortiser under $300, but that’s a very reasonable price for such a productive tool. Most benchtop mortisers run from $400 to $600, and you’ll likely pay over $1,000 for pro models that come on their own stand. Chain mortisers can be $2,000 plus.
Q. Can a router be used as a cheap alternative to a mortiser?
A. The router itself might be less expensive but cutting mortises freehand is not practical or accurate — and mortising jigs for routers can be expensive. Jigs are a viable alternative if you cut lots of different joints, but you will struggle to match the accuracy or productivity of a stand-alone mortiser.
Q. Do mortisers need much maintenance?
A. No. Like any wood shop tool, a regular cleaning at the end of the day and occasional lubrication will help maintain peak performance. Chisels need sharpening periodically, but even for novices it's a fairly straightforward task.
Our take: High-quality tool for the woodworker who needs accuracy and productivity.
What we like: Powerful 3/4 horsepower motor and heavy-duty cast construction. Precise rack and pinion adjustment. Secure fence locking and hold-down. Integrated chisel holder. Handle fits either side of head.
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