Chapter LXVIII: 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.

=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.=

=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.