双导程蜗杆蜗轮是一种具有特殊结构的蜗杆蜗轮传动装置，以下是其含义及特别之处：
含义
双导程蜗杆蜗轮是指蜗杆的齿厚从一端到另一端是均匀变化的，其齿的左、右两侧面具有不同的导程，而同一侧的导程则是相等的。因此该蜗杆又称为变齿厚蜗杆，与之配合的蜗轮也具有相应的特殊齿形。
特别之处
• 可精确调整啮合间隙：能将啮合侧隙调整得很小，经验上可至0.01-0.015mm，而普通蜗轮副一般只能达到0.03-0.08mm。在使用过程中，若因磨损等原因导致间隙变大，可通过轴向移动蜗杆来轻松调整间隙，使蜗轮蜗杆始终保持良好的啮合状态。
• 不改变中心距调整侧隙：普通蜗轮副通过蜗杆径向移动调整侧隙会改变中心距，导致齿面接触变差、加剧磨损。双导程蜗轮蜗杆则采用蜗杆轴向移动来调整啮合侧隙，不会改变中心距，有利于保持蜗轮副的精度和传动性能。
• 调整准确方便可靠：双导程蜗杆通常是用修磨调整环来控制调整量，调整操作相对简单，调整结果准确，且可靠性高，相比之下，普通蜗轮副的径向调整量较难掌握，调整时还容易产生蜗杆轴线歪斜的问题。
• 对安装要求相对宽松：双导程蜗轮副的蜗杆支承在支座上，只需保证支承中心线与蜗轮中截面重合，中心距公差可略微放宽，装配时通过调整环就能获得合适的啮合侧隙。
• 传动精度高：由于可以实现微小的啮合间隙调整，且调整后能保持稳定的啮合状态，因此双导程蜗杆蜗轮在传动过程中能够提供更高的传动精度，可使蜗杆回转背隙小于1个弧分，个别型号能达30个角秒。
Double-pitch worm gear is a worm gear transmission device with a special structure. The following is its meaning and special features:
Meaning
Double-pitch worm gear means that the tooth thickness of the worm changes evenly from one end to the other, and the left and right sides of its teeth have different leads, while the leads on the same side are equal. Therefore, the worm is also called a variable tooth thickness worm, and the worm wheel matched with it also has a corresponding special tooth shape.
Special features
• Accurately adjust the meshing clearance: The meshing side clearance can be adjusted to a very small level, which can be adjusted to 0.01-0.015mm in experience, while ordinary worm gear pairs can only reach 0.03-0.08mm. During use, if the clearance becomes larger due to wear and other reasons, the clearance can be easily adjusted by axially moving the worm, so that the worm gear always maintains a good meshing state.
• Adjusting the side clearance without changing the center distance: Ordinary worm gear pairs adjust the side clearance by radial movement of the worm, which will change the center distance, resulting in poor tooth surface contact and increased wear. The double-lead worm gear uses the axial movement of the worm to adjust the meshing side clearance, which will not change the center distance, and is conducive to maintaining the accuracy and transmission performance of the worm gear pair.
• Accurate, convenient and reliable adjustment: The double-lead worm gear usually uses a grinding adjustment ring to control the adjustment amount. The adjustment operation is relatively simple, the adjustment result is accurate, and the reliability is high. In contrast, the radial adjustment amount of the ordinary worm gear pair is difficult to grasp, and the worm axis is prone to skew during adjustment.
• Relatively loose installation requirements: The worm of the double-lead worm gear pair is supported on the support. It only needs to ensure that the support center line coincides with the middle section of the worm gear, and the center distance tolerance can be slightly relaxed. The appropriate meshing side clearance can be obtained through the adjustment ring during assembly.
• High transmission accuracy: Since a small meshing clearance adjustment can be achieved and a stable meshing state can be maintained after adjustment, the double-lead worm gear can provide higher transmission accuracy during the transmission process, which can make the worm rotation backlash less than 1 arc minute, and some models can reach 30 arc seconds.