Section 77.—SPINDLES AND CENTRES.

[1347]. Spindle with sunk end bearings.

[1348]. Spindle with one sunk bearing and one collar.

[1349]. Plain spindle with two loose collars. Where pedestals with loose caps are used (see [Section 46]) the collars may be solid with the spindle, but with a long shaft the collars should be at one end only as shown, to allow of expansion. A wheel frequently occupies the place of one or both collars, and serves the same purpose.

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[1350]. Coned centre, fixed.

[1351]. Collar centre pin or stud bolt, fixed.

[1352]. Coned centre for roller or similar detail, driven in place.

[1353]. Parallel centre for roller or similar detail, keyed in place.

[1354]. Square centre for crane barrel, &c. See [Nos. 634] and [635].

[1355] & [1356]. Lathe headstock spindles, solid or hollow; sometimes made with conical and sometimes with parallel necks.

[1357]. Conical crane post.

[1358]. Conical cart axle.

[1359]. Universal centres, employed to allow of a machine (or part of ditto), such as a drill, to be adjusted at any possible angle, the machine being fixed to one end of bar A.

[1360]. Railway carriage axle. For cranked axles, see [Section 10].

[1361]. Square neck centre bolt. The square neck prevents the bolt turning and loosening the nut.

[1362]. Coned and cottered crank pin or centre, sometimes secured by a nut, as [No. 1350].

[1363]. Centre pin and bracket, adjustable to various angles.

[1364] & [1365]. Two methods of securing end of rod to any solid part of machine; used for steam hammer heads.

[1366]. Hollow post centre, with water or steam channel to allow for swivelling.

[1367]. Group of sleeve centres, employed to allow of several pairs of lever or wheel motions being taken independently on a single shaft.

[1368]. Ordinary centre pin, with nut, washer, and split pin.

[1369]. Ordinary centre pin, with split pin and washer.

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Section 78.—SCREW GEAR, BOLTS, &c.

[1370]. Square thread screw. Single, double, or multiple thread.

[1371]. V thread screw.

[1372]. Enlarged section of V thread.

[1373]. Strongest thread when the strain is always in one direction.

[1374]. Round thread screw.

[1375]. Geared thread, to be used with ordinary wheel teeth, the section of thread being that of a rack of the same pitch as wheel.

[1376]. Earth screw, screw pile, screw mooring, earth borer. See [No. 530].

[1377]. Fixed screw, with hand wheel to revolve the nut, the screw having no rotation.

[1378]. Conical screw; used for chucks, &c. With two, three, or more sliding jaws chased to fit the conical thread.

[1379] & [1380]. Differential screws. One fixed, the other revolving, impart a motion equal to the difference of pitch of the two screws (see [Section 31]). See [No. 1430].

[1381]. Screw, with half nut; the bearings of the screw being fixed act as a fulcrum for the motion of the half nut, which may be attached to any sliding device; employed for jaw chucks.

[1382]. Screw and worm gear, used for screw jacks, &c. The worm gears with a worm wheel having a central nut running on the main screw.

[1383]. Mutilated screw and nut. In one position the nut can slide on the screw, and a partial turn locks it. Used for instantaneous grip vices, &c.

[1384]. Spiral worm for three or four jaw chucks, expanding devices, &c.

See [Sections 28] and [36].

[1385], [1386], & [1387]. Screw driver heads for screws.

[1388] & [1389]. Hexagon and square heads for ordinary spanners.

[1390]. Form of head requiring special spanner or pointed bar.

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[1391]. Cylinder head bolt, with drilled holes and special spanner.

[1392]. Cylinder head, but with flutes instead of holes for spanner.

[1393]. Cylinder head, but with two flats cut on the head to suit an ordinary spanner.

[1394]. Socket head, to receive a second screw.

[1395]. Eye bolt.

[1396]. Thumb screw.

[1397]. Thumb or shutter screw.

[1398]. Milled head screw.

[1399]. T head screw.

[1400]. Thumb or fly nut and screw.

[1401]. Hexagon collar stud to receive a nut or other female screwed fixing.

[1402]. Bolt head for forked spanner, used for sunk or countersunk heads.

[1403]. Hexagon head, with solid washer or collar.

[1404]. T head bolt for T grooves in castings.

[1405] & [1406]. Countersunk heads.

[1407]. Eye bolt, with flat sides and straight eye for a pin or bolt.

[1408]. Snap head.

[1409]. Hook bolt.

[1410] & [1411]. Lewis bolts, rag bolts.

[1412]. Cottered bolt.

[1413], [1414], & [1415]. Lewis bolts and key pieces.

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[1416]. Collar stud.

[1417]. Split spring head bolt.

[1418]. Hook bolt.

[1419]. Solid head and collar bolt, bed bolt.

[1420] & [1421]. Heads for bolts to slide and turn in T grooves of planing machines, &c.

[1422]. Countersunk bed bolt. Boiler stay.

[1423], [1424], & [1425]. Methods of finishing screw heads to prevent catching passing articles.

[1426]. Screw head, with cross dovetails to carry a key or screwing lever.

[1427] & [1428]. Right and left-hand screw couplings for tie rods, &c.

[1429]. Ring coupling for 2, 3, 4 or more rod ends for tie bracing.

[1430]. Right and left-hand screw couplings with halved ends to prevent the rods turning; may be made with one fine and one coarse thread for differential motion, or with right and left-hand threads.

[1431]. Rifling, as used in ordnance, &c., i.e. an internal multiple screw thread of very long pitch.

[1432]. Screw spanner; the weight prevents it working loose.

[1433]. Belt screw.

[1434]. Gib cotter bolts.

See also pipe couplings, [Nos. 1071, 1072, 1073], [1074, 1075], and [1062], [1068], [1070].

For spiral worms and creepers, see [Section 57].

Spiral pump, [No. 1022].

Note that it is possible to construct a screw with an increasing or decreasing pitch, as is done with the screw propeller. See also [No. 1378].

Double screw gear, [No. 727].

Snail worm gear, [No. 730].

Worm and crown gear, [No. 733].

Worm and spiral gear, see [Section 84].