Dimensions of Screw Elements with Clearances

Mirroring point K on the bisector 5, we obtain point N. The angle between line 9, which connects point N and center M, and the line of symmetry 2 corresponds to the root angle. The profile between the lines of symmetry 1 and 2 is made up of the following arcs Between line 1 and line 7 is an arc with an external diameter, i. e a portion of circle 3. It bends sharply at point K and becomes an arc that is part of circle 7. This in turn passes tangentially over at point N into an arc that is part of circle 4. 

The design of the profile can fail if we make the internal diameter too small. This is the case if point K is outside the lines of symmetry, i. e., the screw can no longer reach the external diameter. 

A pair of screw elements is conveying if the flat profiles are extended into the third dimension by helical rotation. In this case, we speak of screw elements. The pitch T of the element is another important dimension here. In today s modular screws, individual elements each have a constant pitch and a pitch variation is achieved by using different types of element. 

All technical screw elements have clearances between the screws and between the screw tip and barrel wall for the following reasons  

Two more dimensions are added to the geometric parameters of screws s (clearance between the two screws) and 8 (clearance between wall and screws). 

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