The relationship between a mortise and a tenon is comparable to a couple, where the two are united to become one. A mortise and tenon joinery involve a tongue that acts as a peg that fits into a hole called a mortise cut to create a sturdy joinery. Applying an adhesive finalizes the assembly to strengthen the joints. Mortise and tenon consist of three types, such as the notched, blind, and coped mortise and tenon joints for different applications.
History of Mortise and Tenon
The existence of mortise and tenon dates back over 7,000 years. In Leipzig, Germany, archeologists unearthed the mortise and tenon joints in a well. The wooden furniture remains up to these days.
Archaeological studies showed that mortise and tenon had their beginnings during the Neolithic Age as part of reinforcing the wells by adding the wooden lining using the mortise and tenon joinery. Wooden boards of the Khufu Ship use this type of joinery.
Old furniture pieces in the Middle East archaeological sites revealed the use of mortise and tenon joints. Many findings showed that mortise and tenon were famous woodworking joinery.
Chinese architecture uses this joinery to form roof frames, struts, brackets, and beams of houses. Chinese construction employed mortise and tenon joints later in the Neolithic Age.
Ancient shipbuilding used a variation of the M&T technique, known as the Phoenician joints, to assemble the parts of the sea vessel. The method used by the shipbuilders involved two mortises cut into the sides of the two timbers.
Shipbuilders insert a rectangular tenon into the two mortises before locking it with a dowel through a hole (s) that they drilled through the side wall and tenon of the mortise.
How Does a Mortise & Tenon Joint Work?
Mortise and tenon joinery is an ancient construction technique with a history dating back more than 7,000 years. Its strength is so strong that professional woodworkers consider it the second strongest joinery after the dovetail.
The mortise refers to the hole that woodworkers cut into timber. The tenon relates to the tongue, which they insert into the mortise. They work similarly to a square peg that fits into a hole. The mating workpieces adhere after gluing them.
Creating the mortise requires a router, chisel, drill, or press. You will need a table saw, chisel or router, and a hand saw to create the tenon and cut it to the rail’s end. M&T joints can be round, square, or in shape. Woodworkers assemble them at a 90-degree angle or any angle or variation. They insert the timber’s end into a hole using another wood.
The tenon is a small piece of the timber’s end, while the mortise is wood with a hole. Locking the joints of M&T in place requires an adhesive, such as wood glue or pins and wedges. Professional woodworkers can carve the mortise and tenon using their skilled hands. Newbies must use a power tool to get an accurate cut.
Cut the mortise before cutting the tenon to clean out and make an adjustment before fitting it into a mortise. The tenon must have the equal half thickness of the timber, while the length of the tenon must be four to five times the tenon’s thickness.
Difference between a Mortise and a Tenon
Differentiating a mortise from a tenon is not confusing if you look closely at their roles in creating solid woodworking joinery.
What is a Mortise?
A mortise acts as a socket, cavity, slot, hole, groove, or recess that woodworkers cut into a wood piece to connect with the tenon or tongue. It is a joint member to which you place the tenon. The mortise should be about one-third of the material’s thickness.
When using a router, ensure the router bit is almost the same thickness as the material—carbide blades from a reputable manufacturer guarantee efficient artistry.
The rule of thumb is mortise should not be too expansive to prevent weaker cheeks, while a narrow mortise will weaken the tenon. The easiest way to make the mortise and tenon joint is to do the mortises before cutting the tenons. You will need simple tools to make the mortise, such as a mallet and chisel or a fixed table and plunge router.
What is a Tenon?
A tenon is a projection on the timber’s end that woodworkers insert into the mortise.
When tenon and mortise join together, they create a solid joint to hold together some furniture pieces, such as chairs, tables, windows, tool chests, cabinets, doors, building frames, and clocks. The strength of the mortise and tenon joint makes the project stand against stress in daily use.
Woodworking beginners should learn the basics of this joinery technique before learning other types of joineries. For a start, you can make the joints using traditional hand tools to know better about the steps in layout and cutting the tenons and mortises.
Recommended Tools in Making Mortise & Tenon Joints
- Brass wheel marking gauge
- Fine tip pencil
- Marking Knife
- 6″ Combination Square
- Carcass Back Saw
- Dovetail Saw
- Sharp Chisels
- Pig Sticker Mortise Chisel
- Joiner’s Mallet
- Woodworking Clamps
- Woodworking Workbench
What are the Types of Mortises and Tenon Joints
Types of Mortises
Mortises have many variations, such as:
- Haunched mortise -This type is popular in joining door style to rail joints and table rails to stiles or legs near the end. The mortised timber is slightly narrower than the rail’s width except in the spot where the mortise receives the tenon’s base to form a haunch.
- Plain/ simple: A mortise with shoulders on both sides.
- Blind: A mortise with shoulders either on three or four sides.
- Barefaced mortise-It refers to a mortise that has a missing face cheek.
- Stub mortise -This type of mortise has a shallow depth which relies on the timber’s size. Unlike some mortises, it does not pass through a workpiece.
- Open mortise refers to a three-sided mortise.
- Through mortise- It refers to a mortise that passes throughout a workpiece.
- Through-wedged half-dovetail mortise-It refers to wedged half-dovetail mortise that passes throughout the workpiece.
- Wedged-A mortise that has a wedge-like tenon for holding the workpiece.
- Wedged half-dovetail mortise -This mortise has a broader or taller back than its opening or front. It has enough space for tenon insertion.
- Keyed mortise-It refers to a mortise with a wedge-shaped key to hold the workpiece firmly.
Types of Tenons
Here is a list of tenons:
- Hammer-headed tenon-This tenon is popular when tightening the shoulders with a clamp is next to impossible.
- Half shoulder tenon- This asymmetrical tenon has a single shoulder on the side. It is an ideal tenon for door bracing, ledging, and framing.
- Stub tenon-This tenon is shorter than the width of the mortise board.
- Top tenon-It refers to the tenon that takes place above a post.
- Tusk tenon-This tenon uses a key that resembles a wedge to hold the joints.
- Blind/stub tenon-As the name suggests, this tenon is not visible outside as it ends at the inner part of the receiving member.
- Through tenon- It refers to a tenon that goes throughout the workpiece that you insert into the mortise. In making this tenon, lay out the workpiece to allow the tenon to hang out on the other side, making a tick mark.
- Loose tenon- This tenon is the exact opposite of a fixed tenon, where it acts as a separate joint member.
- Biscuit tenon-A type of tenon that resembles a biscuit due to its thin oval shape.
- Pegged/Pinned tenon- This tenon strengthens the joint using a dowel pin or pegs through the drilled holes on the side wall of the mortised part and tenon.
- Teasel/teazle tenon-It refers to a tenon that lies above a gunstock post. The mortised board receives it through the tie beam’s underside.
- Twin tenon -The additional strength comes from two tenons that offer a wider gluing surface.
Steps in Making Mortise and Tenon Joints
Step 1: Layout the Workpieces
This step is essential to get an accurate cut. Lay out the boards on the workbench. Butt the tenon workpiece against the mortise workpiece to evaluate which spot to join them. Scribble the reference marks on the edge and face of each workpiece.
Step 2: Scribble the Mortise Walls and Tenon Cheeks
Use a mortise gauge to scribble the mortise and tenon boards with marks. Mark from the reference face to get the accurate tenon fitting. Place the mortise chisel on your tenon board’s top edge, allowing the inner cutter of the mortise gauge to get in contact with the chisel’s edge.
Mark the inner blade along the tenon’s end (shoulder line-shoulder line) and then run the inner cutter on the mortise board. Place the outer cutter on the same level as the chisel’s outer edge. Mark the outer tenon line around the tenon’s top (shoulder line-shoulder line). Continue marking the external line of the mortise board.
Step 3: Sawing the Tenon Cheeks
Saw the tenon cheeks using a back saw with rip teeth as you will cut down the board’s grain. A dovetail saw is ideal if you cut a small tenon. Cut out a small notch using a bench chisel to guide the back saw to get a straight and flawless cut. Cut at a 45-degree angle before sawing it horizontally across the board’s top-end grain.
Continue sawing at a 45-degree angle down to the shoulder line.
Turn the piece of tenon around the vice, sawing from the outside using the new kerf above the board’s top. Repeat the steps for the other line on the tenon to produce two cuts.
Step 4: Cutting the Shoulders
Use a backsaw with a crosscut tooth or a dovetail saw with small rip teeth for this step. Secure the tenon board against the bench hook, allowing the wooden mallet and bench chisel to deepen the shoulder line. Set the chisel on the shoulder line and let the bevel face the tenon.
Perform 1-2 medium strokes with the mallet. Create a slightly angled ditch as your crosscut carcass saw guide, and place the saw to start sawing straight down. Repeat the steps on the other tenon side.
Step 5: Cutting the Sides of the Tenon
Draw vertical lines using a square on both sides of the tenon. Cut off a tiny bit from both sides using a dovetail saw. Cut the side shoulder pieces using a crosscut carcass back saw.
Step 6: Mortise Layout
After you have made the tenon, it is time to make the mortise. Place the tenon on top of the mortise—scribble tick marks on your mortise where you will insert the tenon. Scribe the marks using a marking knife and square to get the proper mortise outline.
Step 7: Chopping the Mortise
Use a mortise chisel to chop the mortise, ensuring that the mortise board is clamped correctly on top of another workpiece. The mortise line width should be the same as your mortise chisel’s width while the sides slightly touch the marked lines.
The mortise chisel should be one-fourth inch away from the end of the layout lines. Chop the mortise by hitting the top of the chisel with a wooden mallet straight downward.
Continue chopping and remove the chisel from the hole, allowing the chisel to run down the board’s edge slightly. Chop downward once more and continue this step to reach within one-fourth of the mortise’s other end.
Stop chopping and flip your mortise chisel around. Continue chopping towards the other way with the bevel on the untouched area until the hole becomes more profound.
Use a combination square to determine if the mortise length is the same as the length of the tenon.
Stop chopping once the square has bottomed out. Trim your mortise inner edge using a smaller or ¼ inch bench chisel until vertical.
Note: Avoid trimming or paring the edge too much as it loosens.
Dry fit the tenon to determine its tightness. Forcing your tenon to get into the mortise by poking a heavy mallet may crack or split the mortise. If the mortise is smooth and vertical, even too tight, it no longer needs trimming. Instead, trim the tenon using a wood chisel or shoulder plane, taking minor cuts to test the fit.