Differential thread

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Push-through screw with differential thread: while screwing in, both machine parts pull together. When tightening, the thread with the larger pitch (P1) screws into the left component. At the same time, the thread turns with the smaller pitch (P2) through the right component. Since a shorter path is covered with one turn in the thread with the smaller pitch (P2), both components are pulled together and tightened (→ ←).
A bolt rotates through two nuts that have slightly different thread pitches. With each rotation, the distance between the nuts changes by the difference in the thread pitches.
Adjustment mechanism of a micrometer with differential thread. The thread 11 on the bolt 4 has a greater pitch than the thread 10 in the hollow cylinder 1 . One rotation of the handle 12 with the inner threaded sleeve 13 leads to a relative movement between the threaded bolt and the hollow cylinder , corresponding to the difference in the thread pitches.
The thread in the middle component has a different pitch than the two outer threads. With one revolution of the axis AB, the middle component moves by the difference between the two different thread pitches.

Differential thread (also differential thread) describes the combination of two ordinary threads with different pitches that are located on a common axis . When this axis rotates, the components seated on the two threads move relative to one another, which corresponds to the difference in the gradients. This enables a very precise setting of the distance between the two components, which would otherwise only be possible with a very fine thread that would have a correspondingly low mechanical stability.

A screw with a differential thread also enables space-saving and firm clamping of components. The screw has - in different areas of its shaft - two threads with the same thread direction but different pitch P. The thread diameter can also be freely selected. When the components are braced against each other, the screw with a differential thread acts like a normal screw, the thread pitch of which is the difference between the two pitches - that is, relatively small.

The smaller the pitch difference (with the same tightening torque ), the greater the clamping forces.

Similarly, nuts with differential threads can also be designed.

Applications

  • Tool holder of indexable inserts (lathe)
  • Rarely on connecting rods in reciprocating engines if the lower connecting rod eye is split
  • Clamping screw on Morse taper tool holders (e.g. Wabeco)

See also

see also: thread (for the terms: pitch or thread direction)

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