A drawbored mortise-and-tenon joint is held by more than a close fit or a layer of glue. A hardwood peg passes through the mortised member and an intentionally offset hole in the tenon. As the peg is driven home, it pulls the tenon shoulder hard against the face of the mortise.
This is useful in frames that must stay tight through use and seasonal movement: chairs, benches, tables, doors, and timbered cases. It can also simplify assembly, since the joint supplies much of its own clamping force. But drawboring is not a remedy for careless joinery. The mortise walls, tenon cheeks, and shoulders must first fit cleanly. The peg should tighten a sound joint, not force a poor one into submission.
What drawboring does
In an ordinary pegged joint, the holes in the mortised member and tenon line up. A drawbored joint shifts the tenon hole slightly toward the tenon shoulder. When a tapered peg enters, it bends gently through that offset and draws the tenon inward.
The amount of offset is small. Too little gives no meaningful pull; too much can split the tenon, crush the hole, or bend the frame out of square. For typical furniture-scale work, begin cautiously: an offset around 1 mm is often enough. A larger, more robust joint may tolerate a little more, but it is wise to prove the amount on scrap cut to the same proportions and wood species.
The peg also needs to be strong. Straight-grained oak or ash is a traditional choice because it resists shearing and can be shaped into a resilient taper. Avoid short-grained commercial dowels, which may snap at the point of greatest strain.
Photo by Dominik Scythe on Unsplash.
Materials and preparation
Gather the following before beginning:
- Straight-grained hardwood for the rail, stile, leg, or other frame members.
- Riven or carefully split oak or ash stock for pegs.
- A mortise chisel, mallet, tenon saw, marking gauge, knife, and square.
- A brace or hand drill with a sharp auger bit matching the intended peg diameter.
- A small awl or bradawl for locating hole centres.
- A tapered reamer or knife, if you wish to ease the entrance of the peg holes.
- A block plane, spokeshave, drawknife, or knife for shaping pegs.
Choose a peg diameter that suits the scale of the joint. A peg that is too small contributes little strength; one that is too large removes excessive wood from the tenon and mortised member. For many furniture joints, a moderate peg is sufficient. Keep sensible material around every hole, especially at the end and edges of a tenon.
Work with dry, stable stock. If the frame pieces are still changing markedly in moisture content, neither precise shoulders nor a drawbore offset will behave as predictably as they should.
1. Cut and fit the mortise and tenon first
Lay out the mortise and tenon with a marking gauge set from the same reference face and edge. This gives the joint a common centreline even when the stock varies slightly in thickness.
Chop or bore and pare the mortise square and true. Saw the tenon cheeks and shoulders carefully, then refine only as needed. The tenon should enter with firm hand pressure or light mallet taps. Its shoulders should meet the mortised face evenly all around.
Do not proceed until this dry fit is satisfactory. A drawbore peg can conceal a gap during assembly by pulling one part against another, but it cannot correct a twisted shoulder, a bottomed-out tenon, or a mortise that is out of square.
If the joint will be glued, decide now whether glue is appropriate for the piece. Drawboring can be used with or without glue. In a permanently glued furniture frame, the peg adds mechanical security and visual character. In work intended to be repaired or disassembled, it may be preferable to rely on dry joinery and pegs alone.
2. Lay out the peg hole in the mortised member
With the joint assembled dry, mark the peg location on the outer face of the mortised member. Keep the hole far enough from the member’s edges that drilling will not weaken a narrow stile or leg.
For a single peg, place it where it will pass through sound material near the middle of the mortise length. In a wider or longer tenon, two pegs may be appropriate. Arrange them with enough space between them that the wood is not reduced to a fragile strip. Their purpose is to hold the shoulders closed, not to turn the tenon into a row of perforations.
Use an awl to establish the centre. Drill through the mortised member at a right angle to its face. A brace gives a slow, controlled cut and makes it easier to follow a square held alongside the bit. Back the work with scrap if possible to reduce breakout as the bit emerges.
Bore cleanly through both mortise walls in one operation when the joint design allows. This keeps the outer holes aligned. If the member is too thick for a clean pass, drill from each face with careful layout and a reliable reference line.
Photo by Fleur on Unsplash.
3. Transfer the hole location to the tenon
Reassemble the joint fully, with the shoulders seated. Insert a pointed transfer tool through the drilled hole and press or tap lightly to mark the tenon. A purpose-made drawbore pin is useful, but a sharpened nail or awl can serve if it makes a clear, centred prick without enlarging the hole.
Take the joint apart. The prick mark shows where the peg hole would be if it were an ordinary pegged joint. The drawbore hole must be moved slightly toward the tenon shoulder.
With a knife or awl, make a new centre mark just inside that transferred mark, toward the shoulder. Keep the movement on the joint’s length, not toward either tenon cheek. This is the crucial offset.
For a first attempt, resist the temptation to make the offset dramatic. A small movement creates a surprising amount of pull once a tapered hardwood peg is driven. If uncertain, make a test mortise-and-tenon from offcuts and use the same bit, peg stock, and proposed offset.
4. Drill the tenon hole
Support the tenon firmly on a sacrificial block. Drill squarely through the tenon at the new offset mark. The hole must remain centred between the cheeks. If it drifts toward one face, the peg may break through the cheek or leave too little wood to resist splitting.
A sharp auger bit will leave a clean hole, but slow drilling still matters. Let the screw lead pull the bit gently rather than forcing it. Withdraw once or twice to clear chips, particularly in dense hardwood.
After drilling, lightly chamfer the entrance and exit of the hole with a knife or countersink. This removes fragile arrises that might otherwise lift or chip when the peg bends through the joint.
Inspect the tenon. There should be adequate material between the hole and the shoulder, end, and cheeks. If the hole is uncomfortably close to an edge, do not try to rescue the joint with a thinner peg. It is usually safer to make a new tenon or revise the joint proportions.
5. Make sound tapered pegs
Split peg stock from straight-grained oak or ash when possible. Splitting follows the grain and reveals whether the fibres run continuously along the length. A peg made from uninterrupted grain is far less likely to shear while being driven.
Plane, shave, or pare the blank into an even round or slightly faceted peg. Make it a close fit for the drilled hole, then taper the first third to half of its length. The point should be rounded rather than needle-sharp. A sharp point can wander, while a gradual taper finds the offset hole and begins bending the peg progressively.
Leave the rear portion near full diameter. It is this section that eventually fills the hole and holds the joint. Test the peg in an offcut drilled with the same bit: it should enter readily at first, then require firm resistance as the full section approaches.
Prepare more pegs than the job requires. If one begins to split, bends badly, or proves undersized, replace it rather than continuing with a doubtful piece.
Photo by Dominik Scythe on Unsplash.
6. Assemble and drive the peg
Dry-assemble the complete frame before applying glue. Check that all shoulders close and that the frame remains square. A drawbore peg exerts considerable force; it is better to discover an assembly problem before glue and pegs make it difficult to correct.
If gluing, apply a modest, even coat to the mortise walls and tenon cheeks. Avoid filling the peg holes with excess glue. Glue can lubricate the peg at first, but it can also create hydraulic pressure in a blind mortise or make a later repair needlessly difficult.
Bring the shoulders fully home. Insert the tapered peg from the most visible or preferred face, then drive it with controlled mallet blows. Watch the joint as the peg advances. The shoulder gap should close rather than the frame shifting out of square.
If the peg stops abruptly long before it is seated, pause. Do not answer every resistance with harder blows. The peg may have met the edge of the offset hole, the tenon may not be fully seated, or the offset may be too severe. Withdraw the peg if possible, inspect the joint, and correct the cause.
When the peg is seated, allow any glue to cure as required. Saw the peg proud for a traditional raised detail, or trim it near flush with a fine saw and pare it level with a sharp chisel. A slight chamfer around the finished peg can soften the edge and reduce splintering.
Mistakes worth avoiding
Offsetting the hole in the wrong direction
The tenon hole moves toward the shoulder, not toward the end of the tenon. Moving it outward causes the peg to draw the tenon away from the joint face rather than pull the shoulder tight.
Using a large offset without a test joint
A drawbore is a controlled bend in wood. Excess offset can split the tenon along the grain, deform the mortise, or make assembly impossible. Start small and test when changing joint size, peg diameter, or species.
Making pegs from short-grained stock
The peg is under bending and shear as it follows the offset. Grain that runs out through the peg creates a weak point exactly where strength is needed. Select long, straight fibres and reject questionable blanks.
Driving a dry peg too aggressively
A very dry peg can be brittle, especially in dense hardwood. It should be well made and properly tapered, not forced as though it were a nail. A few deliberate strikes provide more information than a rapid series of heavy blows.
Asking the peg to close a bad joint
Drawboring is strongest when the tenon already fits and the shoulder is nearly home. Correct gaps, twist, and poor shoulder cuts with tools before assembly. The peg should provide final tension, not structural improvisation.
A quiet, durable detail
A well-made drawbored joint has an uncomplicated logic: the frame is held together by its own wooden parts. The visible peg is not merely decorative, though it may become a pleasing feature. It records the joint’s mechanical work.
Practice first on a simple rail-and-stile joint, using a modest offset and a single peg. Once the sequence becomes familiar—fit, drill, transfer, shift, bore, taper, drive—it becomes a dependable method for frames that need to remain close and honest under use.