Trammel
Compass-points attached to sleeves which slide on a bar or beam. They are used for describing larger circles than an ordinary compass will reach. They are held fast at any point on the bar by a set-screw on the top. Tramping, or Treading, is a method of ramming which, when thoroughly understood, is of great value to the moulder, owing to the fact that upon an equal thickness of sand a man's weight applied at every portion must result in an equal depression all over, and thus produce a rammed surface of equal density at every part. Tramping is much practised by light-work moulders, who roll all their work over in frame nowels with follow and bottom boards, as well as by those employed on heavy work, when mould-beds are formed in the floor. If this operation is not performed with judgment and care, the casting will most assuredly betray the moulder's ignorance or neglect; alternate heavy and light treading being unmistakably revealed by the undulating appearance of the casting's surface. A swelled casting is an abomination, but it may always be avoided by intelligent ramming and tramping. See RAMMING; VENTING.