There are many ways to form helices including press and die, brake press, incremental presses, and so on, which are largely percussive processes.
The Helical Former is unique as it is the only former that is non-percussive and forms a helix in two strokes. It is technically an extender rather than a press.
For this reason, we do not refer to the forming process as pressing, but as a pull, because that’s exactly what the Helical Former does – it pulls the blank to its first position (which is pitch + springback) and then pushes it to its final position (which is finished pitch), to form a precision helical flight.
There are a number of terms that refer to good form – in other words, the elements that are essential in a precision helical flight
PERPENDICULARITY
This refers to the integrity of the helix on the faces. Good form means that the faces are 90 degrees to the shaft at any point.
TRUE EDGES
This refers to the integrity of the lead and trail edges.
Good form means that the edges are straight and equidistant from each other on the finished helix.
EVEN PITCH
This refers to the consistency of pitch along the edges. Pitch should be identical when measured in a straight line, inside edge to outside edge, at any point on the edges.
REPEATABILITY
This refers to the consistency of Good Form in a production run. Excellent repeatability means that the first helix in a production run should have near identical form to the last helix in a production run.
NEAR IDENTICAL
This refers to the finished dimensions of each helix in a production run. Good form means that each helix is near identical in finished dimensions (and demonstrates excellent repeatability).
A NOTE ABOUT THE MATHEMATICS
Good form relies on accurate mathematics in your design.
Remembering that “helix” quite literally means “twisted curve”, your mathematics must take account of both of the twisted curves that there are in a helix flight – the twisted curve on the OD and the twisted curve on the ID.
They are twisted over different pitch and there must be enough material in the blank to handle the distance each has to move in the pull.
This is completely thrown to the wind when forming square shaft! Please see the Knowledge Base for tricks and tips for forming square shaft with precision results.
Good Form is achieved when there is a balance between good design and good knowledge of the material you are forming.