Also 8–9 tapit, 9 tapet, tappit, tabbot. [app. f. TAP v.2 + -ET; but the use of the suffix is abnormal. Cf. mod.F. tapette a flat piece of wood for driving in corks.]
A projecting arm or part in a machine, which by the movement of the latter comes intermittently into contact with another part, so as to give or receive motion.
1745. Specif. Kay & Stell’s Patent, No. 612. There are likewise fixed in the sliding beam or hollow rowler, at proper distances, sundry tapits.
1824. R. Stuart, Hist. Steam Engine, 114. The pins or tappets [are] fixed on the plug-frame (or tappet rod)…: at the ascent or descent of these pins, they strike on the ends of the levers or spanners … connected with the valves,… and open or shut them.
1831. J. Holland, Manuf. Metal, I. 241. As the wheel shaft revolves, the tappits successively strike the hammer tail.
1839. Ure, Dict. Arts, etc., 1287. T is the shaft of the eccentric tappets, cams, or wipers, which press the treddle levers alternately up and down.
1870. J. M. Nutter, in Eng. Mech., 4 March, 610/2. Much depends upon the description of loom and make of tabbots in treading motion.
1907. Westm. Gaz., 28 Nov., 4/1. The inclined valves and new valve tappets … mark it [a motor car engine] with a distinctiveness all its own.
b. attrib. and Comb.; appositive, ‘that is a tappet,’ as tappet-arm, -lever, -pin, -plate; ‘of a tappet or tappets,’ as tappet action, -bevel, -bowl, motion; ‘having or worked by a tappet or tappets,’ as tappet-port, -rod, -valve, -wheel.
1824. Tappet rod [see above].
1837. H. Stansfeld in Civil Eng. & Arch. Jrnl., I. 54/2. Certain Machinery of a Tappet and Lever Action.
1839. Ure, Dict. Arts, etc., 1287. Heddle leaves, actuated by the tappet wheels upon the axis Q.
1895. Model Steam Engine, 46. Simply altering the position of the tappet lever by means of two screws.
1908. Westm. Gaz., 28 April, 4/2. The valve-stems may be lengthened or the tappet-ports enlarged.
