Mortise-And-Tenon Joint

Techniques

In this except from Wood Joints By Machine & By Hand, expert woodworker Randall A. Maxey goes through the steps of the tongue and groove joint.

Wood joints book cover, machine and hand techniques.

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Table of Contents

By hand
- Mortise
By machine

A mortise and tenon joint earned its reputation over the millennia as a very strong joint used in carpentry and furniture construction. You’ll find it used in cabinet face frames, panelled doors, and table bases, to name just a few examples.

Woodworker using mortise and tenon joint technique

Wooden joinery detail with labelled parts and dimensions. — A tenon, or tongue, formed on the end of one piece fits into a mortise (slot) on the adjacent piece. The mechanical connection provides plenty of glue surface to create a time-tested, strong joint

By hand

It’s a debate among woodworkers whether you should make the mortise first or the tenon. If you choose to make the mortises first, it’s easier to fine-tune the fit of the tenon for a strong joint. However, if you choose to make the tenon first, you can use it to lay out the mortise size. My preference is to make the mortise first and fit the tenon later. Here, I lay out the mortise and the tenon at the same time but cut the mortises first.

Tools needed:

Saddle square
Marking gauge
Chisels
Saws

Mortise

Wooden boards with shavings on workbench — 1. A mortise is an open slot that accepts a tenon. There are a variety of methods you can use to cut mortises

Person measuring wood with a saddle square. — 2. If you have multiple parts requiring mortises, gang them together as shown to keep the mortise location consistent. Lay out the location and size of mortise on the workpiece. Use a square to keep the ends of the mortise square to the face of the workpiece

Person using marking gauge on woodwork project — 3. A marking gauge creates precise, incised lines that mark the sides (cheeks) of the mortise. When sizing the width of the mortise to be cut with chisels, use the width of the chisel as a guide

Tip: When using a marking gauge to lay out the mortises and tenons, marking from each face of the workpiece without changing the gauge distance will automatically center the mortise on the width of the workpiece.

Woodworker chiselling with clamp and blue shirt. — 4. Use a chisel closest in width to the width of the mortise. Place the chisel on the end of the mortise with the bevel facing the waste (mortise). A couple of firm taps with a mallet define the ends of the mortise

Wood chisel carving a detailed wooden piece. — 5. Use a wide chisel to deepen the scored lines defining the length of the mortise. Use caution here. Tapping too hard can split the wood along the grain

Person woodworking with chisel and mallet. — 6. A mortise chisel features a thick, strong blade designed for chopping and prying waste out of the mortise. You can also use a standard bench chisel but use care when prying to avoid breaking the blade. Tap firmly along the mortise, creating smaller chips to remove

Person chiselling wood with a mallet and clamp. — 7. Use the chisel to remove the chips. You don’t need to go too deep. You’ll work in stages, gradually working to the full depth of the mortise

Craftsman chiselling wood with precision tool. — 8. After removing the chips, repeat the process of defining the ends and walls of the mortise, then prying out the chips as above. Clean out the bottom of the mortise to create a flat bottom

Person using cutting tool on wood piece. — 9. Now you’ll lay out and cut the tenon to fit the mortise. Most of your layout work here is best accomplished with a marking gauge. It scores clean, straight lines that serve as guidelines for your chisel or saw. Mark the length of the tenon on all four sides of the workpiece using a marking gauge. These lines define the shoulders of the tenon

Woodworker using marking gauge on timber. — **10.** Reset the marking gauge to define the thickness of the tenon, using the mortise width as a guide

Tip: Marking the mortise width and tenon thickness at the same time with the same setting on the marking gauge creates a more accurate joint.

Person adjusting woodworking tool on wooden piece. — **11.** Mark the edge cheeks by starting at one shoulder line, scribing to the end of the workpiece, wrapping around the end, then across the opposite face, stopping at the shoulder line on the opposite face

Carpenter marking wood for precise cutting. — 12. Use a pencil to trace over the scribed lines, making them easier to see when it comes time to form the tenon

Carpenter marking wood for precise cutting and shaping. — **13.** Marking the waste area before making cuts is always a good idea

Person marking wood joinery on workbench. — **14.** To form a groove or “knife wall” for the hand saw, start by defining the shoulders of the tenon with a few firm taps of the chisel placed in the scored layout line

Carving wood with chisel and mallet. — **15.** Position the cutting edge about 1/16in (1.5mm) to 1/8in (3mm) to the waste side of the shoulder line. Make a couple of light taps to remove a narrow chip, creating a shallow groove

Person using a saw on wooden workbench. — **16.** Place the blade of the hand saw in the groove, tight against the shoulder line. Saw down to the line defining the thickness of the tenon

Tip: Cutting the shoulders of the tenon first provides definitive stopping points for the saw when cutting the cheeks of the tenon.

Person sawing wood piece on workbench. — **17.** Use the same process to cut the side cheeks, cutting down to the line defining the width of the tenon

Carpenter using handsaw on wooden plank. — **18.** Orient the workpiece vertically to saw the side cheeks down to the shoulder

Person using woodworking marking gauge on wood plank. — **19.** Use the marking gauge to redefine the thickness of the tenon

Person using a hand saw on wood block. — **20.** Using the edge and end layout lines as guides, saw the face cheeks down to the shoulder line

Woodworker sanding a curved wooden piece — **21.** Check the fit of the tenon in the matching mortise. It’s best to have the tenon too tight rather than too loose. This way, you can sneak up on the fit using planes and chisels

Person using chisel on wooden block — **22.** Pare away excess material using a sharp chisel, cutting down to the layout lines

Carpenter using hand plane on wood project. — **23.** A shoulder plane helps clean up the shoulders of the tenon

Carpenter using a hand plane on wood board. — **24.** The shoulder plane also makes an ideal tool for removing thin shavings until the tenon fits the mortise. Work from both sides to keep the tenon centered

Carving wood with hand planer tool. — **25.** Before assembly, chamfering the edge at the end of the tenon makes it easier to assemble and allows some space for the excess glue

Hands assembling wooden furniture joint — **26.** Make one final test of the fit of the tenon, making any necessary adjustments until it fits snug. If the tenon is too loose, it creates a weak joint

Hand planning wood board using bench plane tool.

WORKSHOP NOTES

Skew block pane

This is a truly versatile plane. It excels at trimming rabbets, working end grain, or making final jointing cuts on boards, plus you can use it in all the ways you would a regular block plane.

The blade is skewed at a 15° angle, which makes cutting easier, either with or across the grain, and helps pull the fence tight against the work. Because the blade sits flush with the side of the body, corner cuts are clean and accurate.

By machine

There are numerous ways to cut a mortise to accept a tenon. A router table and drill press are good options. A mortising machine (mortiser) is specially built for cutting mortises.

Tools needed

By method:

A. Drill press

Bradpoint drill bit
Chisel

B. Router

Straight router bit
Carbide spiral bit—optional
Chisel

C. Mortiser

Square mortising bit
Chisel

A. Drill press

Woodwork drill and sketch on plank — 1. A bradpoint drill bit drills clean holes without skipping or wandering off the target center point

Drill creating hole in wooden board — 2. Drill each end of the mortise, staying just inside the layout lines. Drill holes between to remove the bulk of the waste. You’ll still have to do a little handwork to clean up the walls of the mortise with sharp chisels

B. Router table

Routing wood on a table saw with guide holes. — 2. The holes you drilled slip over a straight router bit in the router table

Three router bits on a red and blue table.

Tip

While you can use any straight bit in the router table to cut mortises, you’ll get better results using a carbide spiral bit. While more expensive than traditional straight bits, spiral bits are designed to cut quickly and cleanly. For routing mortises, look for an upcut spiral bit. It removes chips from the mortise efficiently, keeping the bit cooler.

A spiral upcut bit (center) cuts clean mortises with less burning than traditional straight bits.

Wood being guided through a router table. — 3. When routing mortises at the router table, make several passes, raising the bit between each pass, until you reach the final mortise depth

Using a router table to shape wood. — 4. Layout lines on the front of the workpiece serve as a guide when routing the length of the mortise. You’ll feel when the router bit reaches the predrilled hole at the end of the mortise

Router table with wooden block and sawdust. — 5. After routing the mortise, you can either square up the ends of the mortise with a chisel or round over the corners of the tenon prior to assembly

C. Mortising machine (mortiser)

WORKSHOP NOTES

A mortising machine (below) is similar to, but a much more stoutly built, drill press. It features a movable fence to position the workpiece under the bit and a hold-down to prevent uplift when drilling mortises. The long handle provides leverage for lowering the bit for cutting mortises.

Mortise machine in woodworking workshop.

Right: The square chisel on the mortising bit forms a square hole in the workpiece while the internal drill bit removes the waste and ejects it through the opening in the chisel body.

Metal countersink drill bit for woodworking.

Left: A mortising machine features a specialised bit for drilling square holes. The drill bit fits inside a hallow square chisel

Mortising machine cutting wood for joinery — 1. To drill a mortise, start with a hole at each end to define the length of the mortise

Machine woodworking miter joint in wooden piece. — 2. Drill out the waste by making several overlapping passes, moving the workplace after each pass. Clean up the mortise walls with a sharp chisel

Guide on wood joints by machine and hand.

You can buy Wood Joints By Machine & By Hand from Gifts to Me for only £13.50 (+P&P)! Usual RRP £16.99

Visit giftstome.co.uk and use the offer code R5820

Offer ends 30th May 2025

Mortise-And-Tenon Joint