What distinguishes a single-start thread from a multi-start thread?
Lead screws are surrounded by a bewildering array of terms, so let's simplify things and go back to the fundamentals.
WHAT IS LEAD SCREWS?
Lead screws are mechanical components that transform rotary motion into linear motion.
Lead screws are made of a cylindrical round thread that is spiraled into a screw shape by a single helix throughout its entire length. The threads may have, for instance, a metric thread form, a trapezoidal thread form, or the igus® dryspin® geometry. The dryspin® thread has a high helix thread-like structure.
Let's examine what single threads and multiple start threads are.
L stands for linear travel measured in millimeters per screw revolution.
P = PITCH = Distance between each thread
Single start threads
A single start lead screw can be seen on the lead screw (number 1) on the left. This is distinguishable by having just one thread. A single start is what is meant by this. Because of this, the lead screw's linear travel (lead), measured in millimeters each cycle, is also the distance between the flanks, indicated by pitch.
Multi-start threads
A new thread has been created for lead screw number 2, which is depicted by the green image. This indicates that the lead screw's two-fold stroke is accomplished with a single rotation (lead = 2 x pitch). The thread starts 180 degrees apart, or on different sides. This is categorized as a multi-start thread, sometimes known as a two-start thread.
The third lead screw in this example displays a four-start lead screw. The colors orange, green, purple, and blue denote the beginning of four threads, respectively. Therefore, the linear travel (lead) is four times that of the flanks. The thread's beginning is 90 degrees apart from the other threads.
Visually, many threads are noticeable. By examining the front of the screws, one can easily identify a multiple thread.
Which thread is the most suitable for your application?
It can be difficult to decide whether to utilize single or multiple start threads for your application because each has benefits and drawbacks. A single start trapezoidal thread, for instance, will self-lock, whereas a multi-start thread won't.
Single trapezoidal threads are often self-locking, depending on the coefficient of friction. This effect can only be attenuated with a very low coefficient of friction. The flank angle and the friction prevent the spindle nut or the threaded spindle from moving without external forces being applied. As soon as the static friction is exceeded, the parts are no longer self-locking. Multi-start trapezoidal thread drives have a “rest self-locking” feature. High helix thread drives do not have a self-locking feature.
On the other side, a multi-start thread will allow you to move much more quickly.
ADVANTAGE OF MULTIPLE-START THREADS
When multiple-start threads are used, the effective supporting surface grows when the core diameter stays constant. High helix threads are frequently made with many starts. Benefits of multiple-start threads:
Longer service life results from lower surface pressure.
Due to a lower space between the tooth flanks, the system is more exact.
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