Arc Worms: Transmission Experts Upgraded with "Curved Teeth"
Classification： Blog
Release time：2025-09-09
When talking about worms, you might have heard of straight-sided types like Archimedean worms. But there’s another transmission component that achieves a huge performance leap by "changing tooth shape to curved" — the arc worm. It’s not a single model, but a general term for cylindrical worms with arc-shaped tooth profiles. As a key improvement on traditional straight-sided worms, its core lies in replacing straight teeth with curved ones to significantly boost transmission capabilities.
The advantages of arc worms all come down to their "curved" design. Traditional straight-sided worms have flat tooth surfaces, which easily lead to direct metal-to-metal friction when meshing. In contrast, curved teeth make it easier for a thick hydrodynamic oil film to form when the worm meshes with the worm gear — like adding a "protective pad" to the tooth surfaces, separating the metal and reducing dry friction. This change brings a chain of improvements: their load-bearing capacity is 50% to 100% higher than ordinary worms, and transmission efficiency is also 5% to 10% better — an advantage that stands out even more under high-speed or large transmission ratio conditions. At the same time, less wear means less heat generated by the equipment, greatly extending its service life.
Arc worms mainly fall into two categories, each with its own focus. The first is the Niemann-type arc worm: its tooth profile is a concave arc, while the matching worm gear has a convex arc. This "concave-to-convex" pairing is theoretically capable of achieving optimal lubrication and maximum load-bearing potential. However, it’s extremely difficult to manufacture — it requires specialized arc-shaped turning tools for cutting, followed by grinding with special grinding wheels, placing strict demands on both equipment and tools. The second type is the K-type arc worm (also known as the conical-enveloping cylindrical worm): its tooth profile is a convex arc. Unlike the Niemann type, it’s not directly turned; instead, it’s naturally "enveloped" using a conical grinding wheel (or milling cutter) that moves along the worm’s helical path on a machine tool. While its lubrication performance is slightly inferior to the Niemann type, it’s still far better than ordinary straight-sided worms. Its biggest advantage is excellent machinability — grinding, in particular, is easy to perform, allowing for high-precision tooth surfaces. That’s why it’s widely used in practical industrial production.
Thanks to its high load capacity, high efficiency, and long service life, the arc worm (whether Niemann or K-type) is often used in heavy-duty fields with strict transmission requirements: metallurgical equipment like steel rolling mills and straighteners, mining machinery such as mine hoists and crushers, large chemical equipment, and various high-performance worm gear reducers — these are all its "key battlefields."
In short, the arc worm has achieved a major breakthrough in transmission performance through the small innovation of "changing straight teeth to curved." The Niemann type pursues ultimate performance, while the K-type balances performance and manufacturing convenience. Although it costs more than ordinary worms, it’s an irreplaceable high-performance transmission solution in critical industrial scenarios.
keyword： Arc Worms