How to Drill a Square Hole in Wood

A mortising machine is perhaps one of the best woodworking machines. It is used to make square or rectangular cuts in the wood piece. Some arguments even support that a mortising machine was the first developed machine to drill square holes in lumber.

Before that, people used to make square holes by pressing the square chisel with the help of a lever. Also, a chisel and hammer were used to cut the mortise. However, this all required great effort and time.

With new inventions and innovations, the labour work required is reduced however the efficiency is improved.

If you are confused about drilling the right square by a mortising machine, this article will guide you to accomplish the task efficiently.

Mortising Machine

A mortiser drills out a mortise (a slot) in the work piece which is of essential utilization since long. The mortise is known popularly as a means to join two pieces of wood.

A tenon is another piece of wood projecting a square to fix in the mortise. Simply speaking, the tenon is a peg which fits into the hole i.e., mortise.

Square Chisel Mortiser

When first invented in 1874, this device was manual. It depended totally upon the force exerted by the operator. This force was transferred by lever to the chisel to cut a hole through the timber.

This type of mortiser comprises a four-sided chisel with a drill bit at the bottom. The bit works out to remove the material coming in its way. And the chisel does the finishing task by sharply defining the edges.

Horizontal or Slot Mortiser

This type of mortiser is the latest addition. It contains a router and a sliding table on which the work piece is clamped. Although they can be used to make the traditional tenon and mortise, their speciality is floating tenons.

A floating or loose tenon is one in which the floating tenon fits in the mortises in pieces. Which means that instead of a traditional mortise where a tenon and mortise are joined integrally, several pieces of mortise fit in a loose tenon.

Along with it, there are chain mortisers to drill out larger sized mortises. The one you choose depends upon the intensity of work you want to get done.

Drill press vs Mortiser

A drill press can also be used as a mortiser by utilizing a mortising attachment. However, the machine is not dedicatedly made for this purpose. Which means you might face inefficiency while working with it.

A mortiser, on contrary, is a specialized machine made solely for drilling out square holes in lumber. If you have a long list of square cutting jobs, we suggest you go for a mortiser which is more convenient and less time-consuming.

Steps to Cut Perfect Square Through Wood

The following steps will lead you to drill out squares by a mortising machine:

Step 1: Sharpen your Chisel

The first tool required to drill a neat square in timber is a four-sided chisel. Your chisel should be sharp but not utterly sharp or it might end up deforming the wood.

You can use a diamond cone sharpener to sharpen the edges of the chisel. Simply turn the chisel on the diamond cone while keeping it in perpendicular direction. This will sharpen the chisel from inside. Furthermore, it will leave rough edges on the outside.

After sharpening, your chisel is all set to bore through the wood.

Step 2: Choose the Right Drill Bit

Your four-sided chisel comes with an auger drill bit. Undoubtedly, an auger drill bit is ideal for the task. It has a cutting edge at the end and it looks like a corkscrew.

When the cutting edge drills through the wood, the wooden fibres get inside the clearance between the chisel and the drill bit. The spiral bit contains space for passing the wood grains through them. This will provide you with a clear surface for easily analysing the position of the task.

Step 3: Adjust the Clearance between the Chisel and the Drill Bit

The clearance you want to leave in between the chisel and bit’s cutting edge depends on the type of wood. For softwood, the cutting edge of the drill bit is given more clearance than hardwoods.

Clamp the chisel and drill bit in your mortiser. By the help of the elevation crank and gauge equipped in your mortising machine, you can adjust the height between the chisel and drill bit following the type of wood being drilled.

Step 4: Adjust the Chisel’s Direction

The non-aligned chisel square may lead to tilted or misplaced squares.

Take a wooden rectangular piece to set the chisel square with respect to the fence. Place the piece parallel to the fence of the mortiser. Now lower the bit such that it comes in the length range of the fence.

Start loosening the chisel so that it spins freely. Slide the fence forward. The fence should be forwarded until the fence, wood and chisel are tightly packed with each other.

That point where the wooden piece touches the bit and where the chisel is unable to rotate anymore is your perfect square. Lockdown that position of the chisel.

Step 5: Set the End Point for your Bit

To set the distance down the mortise you want your drill bit to cut through, you will need the piece of wood utilized before.

Use that piece of wood and mark out how far you will go. Bring the bit to that point and raise the stop lock from behind the machine. Your mortiser handle will lock at that point and your bit will not go lower than that point.

Outline the dimensions of the square you want to drill. Set the wood piece under the hold-down. This will fix the wood piece right in position so it does not displace when the chisel comes out after drilling.

Start drilling now at a moderate pace, you will get the work done in a short span of time.


Cutting square holes in lumber for mortise and tenon joints has been an old practice. However, the methods through which the task is achieved changes. The tutorial given will guide you to drill out the square with the most convenient and time sparing machine.

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