Thread direction

Zoe Moser | 9. October 2020

How can I recognise the thread direction of my lead screw?

What is the difference between left-hand and right-hand threads? How can I recognise the thread direction even without a test?

The thread cutting direction right or left can be easily determined with a visual inspection. If you look at the lead screw from the front, you can best see the difference between left-hand and right-hand threads.

Thread direction, right hand

For lead screws with right-hand thread, the thread flanks rise from bottom left to top right (marked orange in our graph). In production drawings right-hand threads are often marked with the letters RH, e.g. TR20x4-RH.

This model is usually preferred by our customers. However, this is often only due to ergonomic requirements, not due to technical differences. The majority of people are right-handed and can therefore apply a greater torque when turning the lead screw clockwise than against it.

Due to the frictional conditions on the wedge, or the inclined plane, tightening a lead screw involves a greater torque than loosening it. The right-hand thread therefore meets these two requirements.

Thread direction left-hand

A left-hand thread rises from bottom right to top left when viewed from the front. Here too, the thread flanks are marked in orange. An alternative designation is the left rising thread. Left-hand threads are usually marked with the letters LH in production drawings, e.g. TR20x4-LH.

What other thread direction does igus offer?

Thread directions other than left and right, are of course, impossible. But what about a combination of both cutting directions?

Our dryspin product range includes not only lead screws with right-hand or left-hand threads, but also reverse lead screws. They offer more flexibility and design freedom for your application. If you would like to learn more about reverse lead screws, you can find out more here.

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