Mortise Holes with Power Drill & Chisel

April 28, 2019 handtools 0 DIY Projects, Woodworking,

This article isn’t about bashing mortise machines. They are without a doubt much faster and more precise than a human with a chisel. But at the end of the day, you can’t own every tool that’s out there. We have to pick and choose which ones to keep in our stable. At Hand Tool Essentials, the mortiser (or mortise machine) didn’t make the cut due to its lack of versatility and high price point. And while a mortising machine would save us time when creating joints, the storage space is also difficult to justify. Thus, we have to cut our mortise holes by hand with a chisel & a power drill. And since most DIYers are in the same boat, we are sharing our experience to help you along.

What’s a Mortise Hole?

Just so we are on the same page, a mortise hole is the receiving end in a mortise and tenon joint. Known for its strength and clean appearance, the mortise and tenon joint is often seen when two boards come together at a right angle. In furniture design, these joints are frequently used on tables, desks, and beds. The tenon tongue, which fits inside the mortise hole, is generally shaven down to a smaller girth than the rest of the board.

Steps to Cutting Mortise Holes by Hand

Drilling Pilot Holes

When it comes to creating mortise holes, some errors are more critical than others. For instance, you probably noticed that our pilot holes weren’t perfectly aligned. Fortunately, this isn’t problematic since the holes are still within the drawn guides. Conversely, keeping your drill bit perpendicular to the board when drilling is crucial to cutting mortise holes. To do this easily, we suggest using a drill press. Selecting the drill bit size is straight forward since you just match the bit’s diameter with the width of the mortise hole. If you don’t have a drill press, consider stepping down a size to allow for less precision.

Chiseling Inward from the Ends

For selecting your chisel, the width of the blade should be the same width as the mortise hole. Beginning with each end of the hole, you’ll want to chisel inward. In fact, the bottom of the chisel blade should match perfectly on the penciled horizontal line when making your first cut. While continuing to insert the chisel into the wood, check to see that the blade is going straight into the board. This will ensure that the cross member sits at the desired height. Upon finishing the ends, work your way towards the middle. This time, you’ll chisel along the side with the bottom of the blade facing outward. The direction of the grain and hardness of the wood species will determine how easily chisel inserts into the lumber.

Cleaning the Edges

Once you’ve completely chiseled out the cavity of the mortise hole, it’s time to soften the edges to hide any errors. While some rogue woodworkers try to skip this step, their work generally suffers as a consequence. For this task, we recommend a combination of sandpaper and wood files. The wood files enable us to easily clean the inside of the mortise hole and smooth out any high points. The sandpaper allows for us to more easily soften the corners and remove splinters. When cleaning the inside of the mortise hole, the main priority is still maintain the dimension of the hole. Removing too much material on the inside can cause for the tenon to fit loosely and jiggle. Upon completing this step, your mortise hole will be ready for a dry fit. Enjoy!

Pro Tip: Don’t attempt to use a mortising bit in a handheld power drill. We’ve tried it…and it doesn’t work. If you attempt to use a mortising bit in your drill press, you’re going to need to retrofit your machine quite a bit.