MACHINE TOOLS The machine tools employed in See also:

• MODERN

The cutters rotate over or against work, between which and the cutters a relative See also:

• MOVEMENT

Hence they are all comparatively small and See also:

• LIGHT

Another thing is that all the old lathes were of dead centre, instead of See also:

• RUNNING

There are obvious advantages in arranging it vertically, the principal being that castings and forgings can be more easily set and secured to a horizontal chuck than to one the face of which lies vertically. The chuck is also better sup-ported, and higher rates of turning are practicable. In recent years these vertical lathes or vertical turning and boring See also:

• MILLS, JOHN (d. 1736)
• MILLS, ROGER QUARLES (1832– )

The slide-rest was designed with this See also:

• OBJECT

Clearly while the self-acting screw-cutting lathe is the best possible machine to use for the first, it is unsuitable for the last. So here at once, from the point of view of screw cutting only, an important divergence takes place, and one which has ultimately led to very high specialization. Small Screws.—When small screws and bolts are cut in large quantities, the guide-screw and change wheels give place to other devices, one of which involves the use of a separate master-screw for every different pitch, the other that, of encircling cutting See also:

• INSTRUMENTS

Then the bar, inserted from the rear-end, is gripped 3y a chuck or collet at the front, the operations of turning, screwing and cutting off done, and the bar then thrust farther through to the exact length for the next set of identical operations to be A, Table, running with See also:

• STEM (O. Eng. staefn, stemn, cf. Du. stain, Ger. Stamm, &c., probably related to " staff ")

In some caseslathe. (See also:

• WEBSTER
• WEBSTER, ALEXANDER (1707-1784)
• WEBSTER, BENJAMIN NOTTINGHAM (1797-1882)
• WEBSTER, DANIEL (1782-1852)
• WEBSTER, JOHN (fl. 1602-1624)
• WEBSTER, NOAH (1758-1843)
• WEBSTER, THOMAS (1773-1844)
• WEBSTER, THOMAS (1800-1886)

But screw-threads have often to be cut on See also:

• OBJECTS

Hollow 0, Cross-slide. mandrel. D, P, Hand-wheel operating screw to travel O. E, Cones keyed to D. F, Split tapered See also:

• CLOSE
• CLOSE (from Lat. clausum, shut)
• CLOSE, MAXWELL HENRY (1822-1903)

M, See also:

• RACK

But when the machines with their tools are once set up, they will run for days or See also:

• WEEKS, EDWIN LORD (1849-1903)

The cam which re-turns D is adjustable but is not in view. c, Feeding cam for turret. d,d,Return cams for turret. e, e,Cams on cam disk for operating the lever f, which actuates the cut-off and forming slide. T, Worm-wheel which drives cam shaft by a worm on the same shaft as the feed-pulley U. V, Handwheel on worm shaft for making first adjustments. W, Change feed disk. g, g,Change feed dogs adjustable round disk. X, Change feed lever. Y, Oil tube and spreader for lubricating tools and work. Z, Tray for tools, &c. number, and they include the usual provisions for ordinary turning.

In some designs change wheels are made use of for imparting a definite movement of cross traverse to the tool, which being compounded with the parallel sliding movements produces the See also:

• TAPER (probably of Celtic origin, cf. Irish tapar, Welsh tampr, taper, torch)

Two lathes are mounted on one bed. A tool will be boring a hole while another is turning the edges of the same wheel. One will be boring, another turning a wheel tire, and so on. The rolls for See also:

• IRON [symbol Fe, atomic weight 55.85 (0=16)]

34, A), and support these on the point centres of headstock and poppet. The angle included by the centres is usually 6o°, and the points may enter the work to depths ranging from as little as in. in very 116 light pieces to i in., a in. or I in. in the heaviest. Obviously a piece centred thus cannot be rotated by the See also:

• MERE
• MERE, ADALBERT (1838-1909)

Steadies.—Pieces of work which are rigid enough to withstand the stress of cutting do not require any support except the centres. A, Travelling steady with adjust- slotted bolt holes a, a; b, b, able studs a, a; b, work; See also:

• BRASS
• BRASS (O. Eng. braes)

• Piece of work. • Turret with box tools. • Turret slide. • Sadule for ditto, adjustable along bed. Screw for locating adjustable slide. • Cut-off and forming cross-slide. • 0, Back and front tool-holders on slide. • Cam shaft. Cam See also:

• DRUM (early forms drome or dromme, a word common to many Teut. languages, cf. Dan. tromme, Ger. Trommel: the word is ultimately the same as " trumpet," and is probably onomatopoeic in origin; it appears late in Eng. about the middle of the 16th century)

B, Stepped mandrel. C, Expanding mandrel. adopted when wheels, pulleys, bushes and similar articles are bored first and turned afterwards, being chucked by the See also:

• BORE

It is a plain disk, screwed on the mandrel A, Screwed hole to See also:

• FIT

As the pressure of the cut would cause an upward as well as back-ward yielding of the work, these two movements are invariably provided against, no See also:

• MATTER

Scroll Chuck. A, Back plate; a, recess for face-plate. B, Pinions. C, Circular rack with scroll b on face. D, Chuck body. E, Jaws fitting on intermediate pieces c that engage with the scroll b. d, Screws for operating jaws independently. A, Back. B, Body. C, See also:

• SPIRAL

39) or a circular rack with pinions (fig. 40), turned with a key which operates all the jaws simultaneously inwards or outwards. But as some classes of jobs have to be adjusted eccentrically, many chucks are of the See also:

• COMBINATION (Lat. combinare, to combine)

The foregoing may be termed the standard chucks. But in addition there are large numbers for dealing with special classes of work. Brass finishers have several. Most of the hollow spindle lathes and automatics have draw-in or push-out chucks, in which the jaws are operated simultaneously by the conical bore of the encircling nose, so that their action is instantaneous and self-centring. They are either operated by hand, as in fig. 31, or automatically, as in fig. 33. There is also a large group used for drills and reamers—the drill chucks employed in lathes as well as in drilling machines. II.—RECIPROCATING MACHINE TOOLS This is the only convenient head under which to group three great classes of machine tools which possess the feature of reciprocation in common. It Includes the planing, shaping and slotting machines. The feature of reciprocation is that the cutting tool is operative only in one direction; that is, it cuts during one stroke or movement and is idle during the return stroke. It is, therefore, in precisely the same condition as a hand tool such as a See also:

• CHISEL (from the O. Fr. cisel, modern ciseau, Late Lat. cisellum, a cutting tool, from caedere, to cut)

We shall return again to this feature of an idle stroke and discuss the devices that exist to avoid it. Planing Machines.—In the standard planer for general See also:

• SHOP

Zm 7 +See also:

• DAM

43.—20-in. See also:

• SIDE
• SIDE (mod. Eski Adalia)

k, Feed disk driven by small gears from cone pulley. j, Pawl driven from disk through levers at various rates, and con-trolling the amount of rotation of the feed screw F. K, Conical mandrel for circular shaping, driven by worm and wheel 1. objection has arisen a new design, the side planer (fig. 43), in which the tool-box is carried by an arm movable along a fixed bed or base, and overhanging the work, which is fastened to the side of the base, or on angle brackets, or in a deep pit alongside. Here the important difference is that the work is not traversed under the tool as in the ordinary planer, but the tool moves over the work. But an evil results, due to the overhang of the tool arm, which being a See also:

• CANTILEVER (a word of doubtful origin, probably derived from " lever," in its ordinary meaning, and " cant," an angle or edge, or else from modern Lat. quanta libra, of what weight)

The mere reversal of the table absorbs much greater See also:

• HORSE (a word common to Teutonic languages in such forms as hors, hros, ros; cf. the Ger. ross)

C, D, Gears driven by cones. E, Shaft of L. F, Tool ram driven from shaft E through disk G and rod H, with quick return mechanism D. J, See also:

• COUNTER

They are therefore laid on the base-plate of the wall planer, and the tool-box travels up and down a tall pillar bolted to the wall or See also:

• STANDING

The weak point in the shaper is the overhang of the arm, which renders it liable to See also:

• SPRING (from " to spring," " to leap or jump up," " burst out," O. Eng., springau, a common Teut. word, cf. Ger. springer, possibly allied to Gr. QnrFpxecOac, to move rapidly)

In the shaper and slotter such See also:

• ACCELERATION (from Lat. accelerare, to hasten, celer, quick)

Many planing machines are portable so that they may be fixed upon very massive work. Several gear-wheel cutting machines embody the reciprocating tool. The strict distinction between the operations of drilling and boring is that the first initiates a hole, while the second enlarges one already existing. But the terms are used with some See also:

• LATITUDE (Lat. latitudo, latus, broad)

The notable exceptions are the vertical boring lathes already mentioned. Obviously the demands made upon drilling machines are nearly as varied as those on lathes. There is little in common between the machines which are serviceable for the See also:

• ODD (in middle English odde, from old Norwegian oddi, an angle of a triangle; the old Norwegian oddamann is used of the third man who gives a casting vote in a dispute)

X, Screw for adjusting the height of the radial arm. Y, Gears for actuating ditto from shaft C. Z, Rod with handle for operating elevating gear. spindle being threaded is turned by an encircling spur-wheel, operated very slowly by a pinion and hand-wheel by the right hand of the attendant, the movement being made independent of the rotation of the spindle. A rack sleeve encircling the spindle is also common. In the power machines gears are also used, but a belt on small cone pulleys drives from the main cone shaft at variable speeds. From three to four drilling and feeding speeds are provided for by the respective cone pulleys. Work is held on or bolted to a circular table, which may have provision for vertical adjustment to suit pieces of work of different depths, and which can usually be swung aside out of the way to permit of deep pieces of work being introduced, resting on the See also:

• FLOOR (from O. Eng. flor, a word common to many Teutonic languages, cf. Dutch vloer, and Ger. Flur, a field, in the feminine, and a floor, masculine)

In each case 'FIG. 46.—Pillar Radial Drilling Machine, 5 ft. See also:

• RADIUS

hand- G vertical shaft an See also:

• ADVANTAGE

C, Upright. D, Spindle or arbor. E, Headstock, carrying bearings for spindle D. F, Tailstock, carrying point centre for tail end of spindle. G, Hand-wheel for effecting adjustment in height of headstock, through bevel-gears H and screw J. K, Cross-bar connecting head- and tail-stocks, and ensuring equal vertical adjustment of the spindle bearings from the screw J. spindle is driven. The latter has its bearings in a carriage which can be traversed along the arm for adjustment of radius. The spindle is counterbalanced. Hand as well as power adjustments are included. In the work-tables of radial and rigid machines there is a great diversity, so that work can be set on top, or at the sides, or at an angle, or on compound tables, so covering all the requirements of practice. Sensitive Machines have developed greatly and have superseded many of the older, slower designs.

The occasion for their use lies in the drilling of small holes, ranging up to about an See also:

• INCH (O. Eng. ynce from Lat. uncia, a twelfthpart; cf. " ounce," and see As)

These machines are used largely in marine engine See also:

• WORKS

.The boring-bar is supported at both ends. In the case of the largest work the boring-bar is preferably set with its axis vertically, and the framing of the machine is See also:

• ARCH
• ARCH, JOSEPH (1826– )

The first very crude milling machine was made in 1818 at a gun factory in See also:

• CONNECTICUT

All pieces which have more than one face to be operated on are done better in the milling machine than elsewhere. All pieces which have profiled outlines involving combinations of curves and plane faces can generally only be produced economically by milling. Nearly all work that involves equal divisions, or pitchings, as in the manufacture of the cutters themselves, or spiral cutting, or the teeth of gear-wheels when produced by rotary cutters, must be done in milling machines. Beyond these a large quantity of work lies on the border-line, where the choice between milling and planing, shaping, slotting, &c., is a matter for individual See also:

• JUDGMENT

This is necessary both to admit pieces of work of different depths or thicknesses between the table and the cutter, and to regulate the See also:

• DEPTH

The latter embodies change-gears likea screw-cutting lathe and worm-gear for turning the head, in combination with an See also:

• INDEX

M, Vertical feed shaft, driven from L through mitre-gears. N, Change gear box. 0, Horizontal feed shaft, operating longitudinal and transverse feed of table through spiral and spur-gears. P, P, Handles for operating changes in feed speeds, nine in number. Q, Handle for reversing direction of motion of table R. S, Hand-wheel for longitudinal movement of table. T, Hand-wheel for effecting cross adjustments. V, Spiral gears indicated for effecting self-acting rotation of circular table W. X, Hand-wheel for rotation of table. Y, Hand-wheel for vertical movements of knee B on screw Z. Machines with vertical spindles (fig. 48) form another great group, the general construction of which resembles that either of the common drilling machine or of the slotting machine.

In many cases the horizontal position is preferable for tooling, in others the vertical, but often the matter is indifferent. For general purposes, the heavier class of work excepted, the vertical is more convenient. But apart from the fitting of a special See also:

• BRACE (through the Fr. from the plural of the Lat. bracchium, the arm)
• BRACE, CHARLES LORING (1826-189o)
• BRACE, JULIA (1806-1884)

They are a comparatively late development, becoming the See also:

• CHIEF (from Fr. chef, head, Lat. caput)

These are milling cutters, though the tools are single-edged ones, hence termed " inserted tooth mills." These are used on other machines besides the rotary planers, but the latter are massive machines built on the planer model, with but one housing or upright to carry the carriage of the cutter spindle. These machines, varied considerably in design, do good service on a class of work in which a very high degree of accuracy is not essential, as See also:

• COLUMN (Lat. columna)

Although this practice is still commonly followed in bevel-wheels of small dimensions, and was at one time the only method available, the practice has been changing in favour of shaping the teeth by a See also:

• PROCESS