Worm gears are similar to crossed helical gears. The pinion or worm has a small number of teeth, usually one to four, and since they completely wrap around the pitch cylinder they are called threads. Its mating gear is called a worm gear, which is not a true helical gear. A worm and worm gear are used to provide a high angular-velocity reduction between nonintersecting shafts which are usually at right angle. The worm gear is not a helical gear because its face is made concave to fit the curvature of the worm in order to provide line contact instead of point contact. However, a disadvantage of worm gearing is the high sliding velocities across the teeth, the same as with crossed helical gears.
Worm gearing are either single or double enveloping. A single-enveloping gearing is one in which the gear wraps around or partially encloses the worm.. A gearing in which each element partially encloses the other is, of course, a double-enveloping worm gearing. The important difference between the two is that area contact exists between the teeth of double-enveloping gears while only line contact between those of single-enveloping gears. The worm and worm gear of a set have the same hand of helix as for crossed helical gears, but the helix angles are usually quite different. The helix angle on the worm is generally quite large, and that on the gear very small. Because of this, it is usual to specify the lead angle on the worm, which is the complement of the worm helix angle, and the helix angle on the gear; the two angles are equal for a 90-deg. Shaft angle.
When gears are to be used to transmit motion between intersecting shaft, some of bevel gear is required. Although bevel gear are usually made for a shaft angle of 90 deg. They may be produced for almost any shaft angle. The teeth may be cast, milled, or generated. Only the generated teeth may be classed as accurate. In a typical bevel gear mounting, one of the gear is often mounted outboard of the bearing. This means that shaft deflection can be more pronounced and have a greater effect on the contact of teeth. Another difficulty, which occurs in predicting the stress in bevel-gear teeth, is the fact the teeth are tapered.
Straight bevel gears are easy to design and simple to manufacture and give very good results in service if they are mounted accurately and positively. As in the case of squr gears, however, they become noisy at higher values of the pitch-line velocity. In these cases it is often good design practice to go to the spiral bevel gear, which is the bevel counterpart of the helical gear. As in the case of helical gears, spiral bevel gears give a much smoother tooth action than straight bevel gears, and hence are useful where high speed are encountered.
蜗杆传动都是单人或双人包络。一个单一的包络传动装置是一个在其中齿轮包裹周围或部分套包虫.. 1传动装置，其中每个元素部分，周边有其他的，当然是双包络环面蜗杆传动。重要两者的区别是，区域联系存在着牙齿的二次包络齿轮，而只有线接触者之间的单包络齿轮。这次的蠕虫和蜗轮的一套具有相同的手螺旋至于越过螺旋齿轮，但螺旋角度通常都不尽相同。螺旋角对蠕虫一般都相当大，这对齿轮非常小。正因为如此，它通常指定牵头角度对蠕虫，它是相辅相成的蠕虫螺旋角，螺旋角对齿轮;两个角度来看都是平等的，为90摄氏度。轴角。
当齿轮是用来传递运动之间的交叉轴，其中有些圆锥齿轮的需要。虽然锥齿轮通常为定轴角为90度。他们可能在制作中几乎任何一个轴角。牙齿的年轻人可能会投下，碾磨，或产生的。只有牙齿产生的，可归类为准确。在一个典型的圆锥齿轮装置，其中的齿轮往往展开舷外的气度。这意味着轴偏转，可以更为突出，并有较大的作用，对接触的牙齿。另一个困难是，它发生在预测应力锥齿轮牙齿，是一个事实，牙齿是锥形。
直锥齿轮是容易设计和简单的制造，并给予了很好的效果，如果他们安装准确，并给予积极评价。在案件squr齿轮，不过，他们也成为嘈杂较高价值的草地线速度。在这种情况下，往往是好的设计实践中去，以螺旋锥齿轮，它是锥对应的螺旋齿轮。在案件的螺旋齿轮，螺旋锥齿轮给予一个更平滑齿行动的机率远高于直锥齿轮，因而是有益的高速，都遇到。
蜗轮又单头或双头的。单头蜗轮是一个齿包在，或部分啮合在蜗论上；齿轮的每一部分都部分地啮合在另一个上，当然就是双头涡轮。两者的重要差别是，双头的齿间是面接触，而单头的线接触。（待译）
