Threaded rod

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Threaded rod

Vitamin

Varilla-roscada-r1.jpg
Threaded metal rod, used as lead screws and for the frame.
Wikipedia none

A threaded rod is a metal rod with threads welded on or rolled out. It is usually used as a frame construction part and as lead screws for the Z-axis. The most commonly used type of threaded rod is a steel M8 (8 mm diameter) one.

Leadscrews

Leadscrews are threaded rods used to lead a component on, for example the X-axis assembly on the Z-axis. For most RepRaps a common threaded rob is sufficient, but for higher precision and reduced wobble you might want to use real leadscrews.

There are two main thread profiles for leadscrews, both of which are trapezoidal: Trapezoidal and Acme. The important but subtle difference is the angle of the thread flank. Be sure to get matching nuts.

Preloading

A common problem when using leadscrews (also for common thread rod ones) is backlash. Because the nut has to be able to rotate freely around the rod, its threading is ever so slightly wider than the rods. Even when the rod is not turning, the nut can move a tiny bit up and down, which is the backlash. Reducing this improves the accuracy of the machine.

A common way to reduce leadscrew backlash is to preload: ensure the nut is in contact with the thread at all times. You can do this using two nuts with a spring in between. This keeps each nut pressed against the thread, reducing backlash. More information and pictures in the article Backlash in Lead Screws: What It is and What to do About It.

Leadscrew vendors

Normal threaded rods are widely available, so there is no vendor table for those. The following table lists Trapezoid and Acme leadscrew vendors.

Vendor (shipping location) Product Diameter Length Pitch Additional notes
HPC Europe (FR/IT) Trapezoidal rolled leadscrew 10-120 mm 1000-3000 mm 2-16 mm  

Leadscrew nut vendors

Normal nuts fit on normal threaded rods and are widely available so the following table lists only Trapezoid and Acme leadscrew nut vendors.

Vendor (shipping location) Product Diameter Pitch Smallest outer diameter Additional notes
HPC Europe (FR/IT) Trapezoidal nut 10-60 mm 2-9 mm 17-90 mm