=Thumb-nut.= A nut so shaped that it may be screwed up or unscrewed by hand.

=Tight.= A term used to denote those parts of a plate or saw that are under undue tension, and prevent the other parts of the plate from lying flat.

=Timber-planer.= A wood-planing machine for thick work, usually having side heads as well as cutter bars.

=Tire.= The iron band surrounding a wheel rim.

=t.i.t-drill.= A drill having a point or teat, and employed to cut flat-bottomed holes.

=Tool-post.= The device employed in a slide-rest to grip the cutting tool.

=Train.= An arrangement of gear wheels in which there are more than two gear wheels employed.

=Trammels= _or_ =tram.= A device for measuring distances too great to be measured by ordinary compa.s.ses.

=Trip-hammer.= A forging machine in which the helve or hammer holding beam is tripped by a revolving cam.

=Trundle.= A gear-wheel having rungs in place of teeth.

=Trying-up.= A term usually employed to indicate that the work is accurately done or fitted.

=Try-square.= A tool having a rectangular back, and a blade whose edges are a right angle to the edges of the back.

=[T] Slot.= A slot or groove, shaped to receive a bolt head and prevent it from turning when the nut is screwed up.

=Turnbuckle.= A socket that receives and holds the ends of two rods and permits either to be revolved independently of the other or the socket to be revolved without revolving either rod.

=Turret-lathe.= A lathe in which a revolving head or turret carries the cutting tools.

=Tuyere= (tw[=e]'ar). The nozzle through which air is forced into a blacksmith's fire, a furnace or a cupola.

=Twin-mills.= Milling cutters that are used in pairs, and have teeth on their side faces as well as upon the circ.u.mference.

=Twist-drill.= A drill having a spiral flute along it.

=Twist-hammer.= A sawmaker's hammer having its two faces parallel, so that by turning it over in the hand its marks will be in opposite directions.

=Two-jawed chuck.= A chuck having two jaws.

U

=Universal chuck.= A chuck in which the jaws move simultaneously.

=Universal joint.= A joint or connection that permits a piece to be moved about in any required direction.

=Universal milling-machine.= A milling-machine that is capable of cutting spirals, and is provided with an index head.

=Upright.= A vertical post or frame.

=U. S. standard thread.= A V-shaped thread having a flat place at the top and bottom.

V

=Vernier= (ver'ni-er). A measuring device in which two sets of lines of division are employed, one set being narrower s.p.a.ced than the other, but so s.p.a.ced that in a certain number of divisions the two end lines of each piece measure exactly alike: this provides a means of making a minute measurement.

=Vise.= A work-holding device in which one jaw is movable and the other stationary.

=Vise-clamp.= A piece of metal placed on the vise jaw and pa.s.sing between it and the work to prevent the jaw teeth from indenting the work.

=[V]-thread.= A V-shaped thread, sharp at the top and bottom.

W

=Warding file.= A thin file suitable for filing out the wards of the keys of door locks, etc.

=Washer.= A perforated disc of metal, usually forming a seating for some other piece as a rest or a pin.

=Wheel lathe.= A lathe for turning wheels.

=Whitworth's quick-return motion.= A mechanism employed to move a cutting tool faster on its return than on its cutting stroke.

=Whitworth's thread.= A screw thread designed by Sir Joseph Whitworth, and having a rounded top and bottom.

=Winding strips.= A pair of straight edges, used to detect any wind or twist in surfaces that ought to be parallel.

=Wing-nut.= A nut having wings so that it may be screwed up with the fingers.

=Wire-gauge.= A gauge having notches in it that are standards of size for wire, for the thickness of sheet metal, for screws, etc., etc.

=Worm-wheel.= A wheel whose teeth are formed to work with a worm or screw.

=Wrench.= A tool for turning nuts, etc.

Y

=Yoke.= A piece that embraces two other pieces to hold them together, or adjust their distance apart.

THE END.