[1548]. Pointed gear; used for light work and for minimum of friction.
[1549]. Curved worm gear, for heavy strains. Several teeth are in gear at once, but the thread, having a varying section and pitch, is difficult to cut.
[1550]. Antifriction worm gear (Hawkins’). The wheel has four rollers; when one pair is nearly out of gear with the worm, the next pair is coming into gear. This worm is also difficult to cut.
[1551]. Crown worm gear.
[1552]. Ball joint mitre gear.
[1553]. Multiplying rack gear. The upper moving rack is driven at twice the speed of the spur wheel rod. The lower rack is fixed; used on planing and printing machines.
[1554] to [1557]. Varieties of worm gear, with straight, hollowed, and curved teeth; the latter are strongest.
[1558]. Worm and rack gear.
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