How to Cut a Mortise and Tenon by Hand

A mortise gauge and mortise chisel are keys to helping make this time-tested joint.

By Chris Gochnour #266-Jan/Feb 2018 Issue

Synopsis: To become proficient in cutting a through-mortise and tenon by hand, you need to use a mortise gauge and a mortise chisel. The mortise gauge is similar to a marking gauge but has two pins—one fixed and one adjustable—and a movable fence that can be locked in place to retain a setting. Mortise chisels are sturdy and can withstand the heavy mallet blows and levering required to remove waste. Chris Gochnour demonstrates how to lay out and cut this fundamental joint using these tools.

This Handwork department builds on the skills from my previous joinery lessons (the half-lap, the bridle joint, and the mitered bridle joint) and adds a mortise gauge and a mortise chisel. I focus on through-mortise and tenons here for two reasons. First, they’re stronger because they offer more long-grain glue surface, and the long grain of the tenon going through the stile helps the stile resist splitting. Second, your frames will more likely be flat and without twist because you mortise halfway through from both edges. Plus, through-mortise and tenons take about the same time as stopped ones.

In this example, the through-mortise is 1⁄4 in. wide by 1-3⁄4 in. long by 2-1⁄2 in. deep—a typical size for a frame-and-panel door. The rail gets the tenon and the stile is mortised.

Two helpful tools

Two tools come in handy when cutting mortise-and-tenons by hand, the mortise gauge and the mortise chisel. A mortise gauge resembles a marking gauge, but instead of one pin, it has two—one fixed and one adjustable. The gauge also has a moveable fence that, once set to the desired position, can be locked in place with a thumbscrew.

Mortise chisels excel at chopping mortises because of their stout construction. They can withstand heavy mallet blows and some levering to remove waste. Plus, the long bevel shears the wood fibers as you drive it downward—a key to mortising.

Layout

Mark the mortise length. Start by marking the rail width on the stile, then measure in 3⁄8 in. to locate the mortise ends. — **Mark the mortise length.** Start by marking the rail width on the stile, then measure in 3⁄8 in. to locate the mortise ends.

Set the mortise gauge using the chisel. Adjust the pins so the 1⁄4-in. chisel drops just inside them. Keep this setting for the whole process. Set the fence to center the mortise on the stock. — **Set the mortise gauge using the chisel.** Adjust the pins so the 1⁄4-in. chisel drops just inside them. Keep this setting for the whole process. Set the fence to center the mortise on the stock.

Scribe the mortise walls. Run the gauge between the end lines of the mortise on each edge of the stock. Make sure to reference off the show face. — **Scribe the mortise walls.** Run the gauge between the end lines of the mortise on each edge of the stock. Make sure to reference off the show face.

Knife the mortise ends. With the mortise walls scribed, knife the mortise ends along the pencil lines, starting and stopping at each scribe line. The knifed line will register your chisel when you chop. — **Knife the mortise ends.** With the mortise walls scribed, knife the mortise ends along the pencil lines, starting and stopping at each scribe line. The knifed line will register your chisel when you chop.

Use the same gauge setting for the tenon

Lay out the tenon shoulders. The length of the tenon should equal the width of the stile. Use a knife and square to wrap the shoulder line around the piece. — **Lay out the tenon shoulders.** The length of the tenon should equal the width of the stile. Use a knife and square to wrap the shoulder line around the piece.

Mark the cheeks. With the mortise gauge at the same setting, and again referencing off the show face, scribe the edges and end of the rail. — **Mark the cheeks.** With the mortise gauge at the same setting, and again referencing off the show face, scribe the edges and end of the rail.

Scribe the tenon’s width. Mark 3⁄8 in. from both edges. Scribe the ends only. After you cut the cheeks, bring these marks down the tenon. — **Scribe the tenon’s width.** Mark 3⁄8 in. from both edges. Scribe the ends only. After you cut the cheeks, bring these marks down the tenon.

The hand-cut mortise and tenon sprd img From Fine Woodworking #266

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