=Scarf.= The bevel of a piece of metal that is to be lap welded.

=Sc.r.a.per.= A hand tool that sc.r.a.pes rather than cuts the metal.

=Screw-cutting lathe.= A lathe that has a screw feed with change gears to enable it to cut threads or screws upon the work.

=Screw-cutting lathe with independent feed.= A lathe that has a lead screw for cutting threads and a separate feed motion for ordinary tool traverse.

=s.c.r.e.w.i.n.g-machine.= A machine used to cut screw threads.

=Screw-machine.= A form of lathe in which the spindle is hollow and a revolving head or turret is employed to carry the cutting tools.

=Screw-plate.= A tool for cutting external threads on small work.

=Screw-thread.= The thread upon a screw or other piece of work.

=Screw-tool.= Another name for a chaser.

=Scribing-block= _or_ =surface-gauge.= A tool that carries a needle or scriber for marking on work lines denoting its finished size or the amount of metal that is to be cut off, and that is also used for setting work.

=Second-cut file.= A file whose teeth are coa.r.s.er than a _smooth_ file and finer than a b.a.s.t.a.r.d file.

=Sector.= A device used in connection with an index plate to denote the holes to be used in any particular division of a circle.

=Segment.= A piece having the shape of a segment of a circle, used for building up a hollow cylinder.

=Segmental saw.= A saw that is composed of parts secured to a frame or disc.

=Self-acting lathe.= A lathe having an automatic feed motion for the cutting tool.

=Set.= 1. The bend to one side of the body of the blade of the teeth of saws. 2. Adjustment or alignment. 3. Binding two pieces together.

=Set-screw.= A screw that binds or secures two pieces together by being screwed through one piece and against the other.

=Shafting-rest.= A slide rest carrying several cutting tools and usually employed for turning shafting in the lathe.

=Shake.= A crack in timber.

=Shank-mill.= A milling machine cutter that is provided with a shank or stem.

=Shaper-centres.= A chuck in which the work is held between centres.

=Shaper= _or_ =shaping-machine.= 1. A machine for cutting such surfaces on iron work as can be cut by a tool travelling in a straight line. 2. A woodworking machine in which cutting tools are revolved on an upright spindle projecting above a work table.

=Shavings.= The cuttings from a paring tool.

=Sh.e.l.l.= 1. The body of a steam-boiler. 2. An outer casing.

=Sh.e.l.l-reamer.= A short reamer that is driven by fitting to a coned mandrel.

=Shimer-heads.= A form of cutter head for woodworking machines, in which circular cutters are used.

=Shingle saw.= A saw thick in the body and beveled off for about two or three inches of its outer diameter.

=Shooting-board.= A device upon which pieces are held when required to have their ends dressed to exact shape or angle.

=Shrinkage-fit= _or_ =contraction-fit.= A means of securing two pieces together by leaving the hole of one too small to receive the other, and then expanding the piece containing the hole so that it will go on and bind fast as it cools and contracts.

=Side-chisel.= A machinist's chisel shaped to cut on the sides of slots or keyways, and having its cutting edge on one side of the end facet.

=Side-tool.= A tool used to cut the ends of lathe work that is held between the lathe centres.

=Single-geared lathe.= A lathe in which there is no back gear.

=Single-riveted joint.= A joint having but one row of rivets in a lap joint and one row of rivets on each side of the plate joint in a b.u.t.t joint.

=Single-thread.= A screw thread having a single spiral.

=Skew-bevel.= A bevel gear wheel in which the teeth sides do not form lines radiating from the wheel centre, but point to one side of it.

=Skew-chisel.= A carpenter's chisel in which the cutting edge is not at a right angle to the body of the tool.

=Skew-cutter.= A cutter in which the cutting edge does not stand parallel to the axis of the shaft that drives it.

=Slab.= 1. A rough square piece of iron forged from sc.r.a.p. 2. The first piece cut from the side of a log of wood.

=Sleeve.= An enveloping piece that is usually cylindrical and too long to be termed a ring.

=Slide-valve.= The valve that governs the admission of steam into and its exhaust out of a cylinder.

=Slot.= A rectangular pa.s.sage or hole pa.s.sing entirely through the material.

=Slotting-machine.= A machine having a vertical bar or ram that carries the cutting tool on its lower end and has a vertical reciprocating motion.

=Smooth-file.= The finest cut of file that is made for ordinary use.

=Smoothing-plane.= A carpenter's short plane for producing a smooth surface.

=Socket.= A piece that is hollow and receives another.

=Socket-wrench.= A wrench that envelops the whole of the head of a bolt.

=Solid milled cutters.= Cutters for woodwork, in which an irregular shaped cutting edge is obtained by recesses cut in the flat face of the cutter.

=s.p.a.ce= _or_ =s.p.a.ces.= The opening between the teeth of gear wheels.

=Spanner.= A form of wrench.

=Spindle.= A shaft that is used to transmit purely rotary motion, and that is usually of small diameter in proportion to its length.