The mortise and tenon joint has been used for thousands of years by woodworkers around the world to join pieces of wood, mainly when the adjoining pieces connect at an angle of 90°. In its basic form it is both simple and strong. Although there are many joint variations, the basic mortise and tenon comprises two components: the mortise hole and the tenon. The tenon, formed on the end of a member generally referred to as a rail, is inserted into a square or rectangular hole cut into the corresponding member. The tenon is cut to fit the mortise hole exactly and usually has shoulders that seat when the joint fully enters the mortise hole. The joint may be glued, pinned, or wedged to lock it in place.
This joint is also used with other materials. For example, it is a traditional method for stonemasons and blacksmiths.
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A mortise is a cavity cut into a timber to receive a tenon. There are several kinds of mortises,[1]:
A tenon is a projection on the end of a timber for insertion into a mortise. Usually the tenon is taller than it is wide.
There are several kinds of tenons:
Generally the size of the mortise and tenon is related to the thickness of the timbers. It is considered good practice to proportion the tenon as one third the thickness of the rail, or as close to this as is practical. The haunch, the cut-away part of a sash corner joint that prevents the tenon coming loose, is one third the length of the tenon and one sixth of the width of the tenon in its depth. The remaining two-thirds of the rail, the tenon shoulders, help to counteract lateral forces that might tweak the tenon from the mortise, contributing to its strength. These also serve to hide imperfections in the opening of the mortise.
This is an ancient joint and has been found joining the wooden planks of the "Khufu ship",[2] a 43.6 m long vessel sealed into a pit in the Giza pyramid complex of the Fourth Dynasty around 2500 BC. Evidence of these joints has also been found in the 4800 year-old wooden ruins some archaeologists are calling "Noah's Ark" in Ankara.[3]
It has also been found in ancient furniture from archaeological sites in the Middle East, Europe and Asia. In traditional Chinese architecture, wood components such as beams, brackets, roof frames and struts were made to interlock with perfect fit, without using fasteners or glues, enabling the wood to expand and contract according to humidity.[4] Archaeological evidence from Chinese sites shows that by the end of the Neolithic, mortise and tenon joinery was employed in Chinese construction.[5]
The thirty sarsen stones of Stonehenge were dressed and fashioned with mortise and tenon joints before they were erected between 2600 and 2400 BC.
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