Halved Lap Splice

The Halved Lap Splice joins two similar components in their length, whilst maintaining the same cross sectional area throughout.

The strength of the joint is almost entirely down to the long grain to long grain glue surface area, and is proportional to the length of the lap.
The joint components are prepared square and true all round, and the joint ends sawn square and preferably shot square with a plane.
The length of the lap is then knifed across opposite faces of the components.
A marking gauge, set to half the component thickness, is used to mark the lap line on the component edges,

and the ends.
The waste area is marked to avoid confusion,
and the knife lines on the faces, are joined to the lap line with knife lines guided by a try square.
Here we can see the waste area, fully defined by knife and gauge lines.

Before sawing, a knife wall is revealed by paring from the waste into the knife line.
The knife wall helps to locate the saw accurately, ensuring the saw kerf is entirely within the waste.

The shoulder is sawn down to the lap line,
and then the cheek is sawn down to meet the shoulder cut.

The saw is 'aimed' so as to follow the lines on both the end and one edge, sawing at an angle,
until the shoulder is reached.
Then the remaining cut is made, with the saw guided within the already made kerf, and down the opposite edge,
until the waste falls away.
The sawn surface is cleaned with a wide chisel,
or a shoulder plane, until it is perfectly flat, and co-planar with the lap lines.
The shoulder cut is pared square to the face, and back to the knifed lines.
Once cleaned up, the two components should mate perfectly, with no gaps.

The joint is then glued, and clamping pressure applied across the faces.

Now watch the video:

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