Also 8 triboulet, 9 treblett, tribolet. [= F. triboulet in the sense ‘wooden cylinder used by goldsmiths for rounding articles’ (Littré); of uncertain origin: see Littré.] A cylindrical rod or mandrel used for forging nuts, rings, tubes, etc., or for drawing lead-pipe. Also attrib.: triblet tubes, thin tubes which slide one upon the other, as in a telescope.
1611. Cotgr., Triboulet, a Triblet; the toole whereon Goldsmiths and Clockmakers put Rings, and little wheeles, when they file, or otherwise worke, them.
1736. Ainsworth, Lat. Dict., I. A triblet, or triboulet (goldsmith’s tool for making rings).
1778. Nairne, in Phil. Trans., LXVIII. 854. In the uppermost room stood a large iron triblet, of about three feet in height.
1853. Ure, Dict. Arts, I. 724. A mandril,… which consists of a long rod of iron, having a short steel treblett on its end.
1877. Knight, Dict. Mech., s.v., The nut having been cut from the bar, the hole is punched and enlarged by the triblet.
1895. Model Steam Engine, 95. Triblet drawn tube (i. e., tube made by drawing a steel mandrel through the inside as well as drawing the outside through a hole).
