1. lit. Each joint of the knuckles (of the hands), or the joint of the leg of an animal called a knuckle.
2. Mech. A joint or coupling forming a connection between two parts of a mechanism, in which a projection in one is inserted into a corresponding recess in the other (like the knuckles of the two hands when clasped or placed together); also extended to other joints, such as universal joints.
1863–9. Dict. Archit., Knuckle joint. An old name for a rule joint.
1873. Spon’s Dict. Engineering, 2663. The knuckle-joint, at the back of the vibrating form-frame.
1881. Young, Every Man his own Mechanic, § 819. Some of these racks are fitted in the centre with a grooved joint technically called a ‘knuckle joint.’
1887. D. A. Low, Machine Draw. (1892), 100. Form of ordinary knuckle joint.
Hence Knuckle-joint v.
1900. Westm. Gaz., 27 Dec., 5/3. The plates will be placed on in dovetail fashion,… the Herreshoffs having decided that the plan of *knuckle-jointing them was not feasible.
