[f. TAP sb.1 + HOLE sb.]
1. The hole in a cask, vat, or the like, in which the tap is inserted.
1594. Plat, Jowell-ho., III. 10. These halfe tubs hauing tap-holes within.
1707. Mortimer, Husb. (1721), II. 322. Put it back again, stopping your Tap-hole.
1628. Folkingham, Panala Medica, iii. 21. An ordinary Stand, Steine or Ale Can with a Tap-hole, will be an apt vessell to serue well for the Infusion.
1689. Worlidge, 2nd Pt. Syst. Agric., ix. 71. I have seen broad and shallow Cases of Board, made and lined in the inside with this Lead, with a Tap-hole at the one Corner of each, and a Plug of Wood fitted to it.
2. A small opening in a furnace, through which the metal, or slag, or both, may be run out; also, a hole in a cementation furnace in which tap-bars (see TAP sb.1 6) are inserted.
1825. J. Nicholson, Operat. Mechanic, 341. Each pot has also small openings in its end, through which the ends of two or three of the bars are left projecting in such a manner, that by only removing one loose brick from the external building, the bars can be drawn out…; these are called the tap-holes.
1839. Ure. Dict. Arts, 320. In the melting furnaces, the metal is run out by a tap-hole in the side.
1861. Fairbairn, Iron, 101. The fluid iron, as it flows from the tap-hole, is fully white hot, and perfectly limpid.
