A scroll chuck uses a rotating spiral scroll engaged with teeth on radially guided jaws so scroll rotation moves the jaws together. This calculator is a signed Archimedean-scroll travel comparison, not a clamping, accuracy or runout model.
Universal Chuck Interactive Calculator
Enter a mathematical starting coordinate, scroll pitch, signed scroll turns and a radial backlash allowance. Results are ideal signed geometric values—not jaw position, gripping diameter, TIR, accuracy, force, capacity or safety guidance.
Equation Used
- An ideal Archimedean scroll with constant entered radial pitch per revolution.
- Each ideal jaw engagement follows the same signed radial advance.
- The entered starting coordinate is a mathematical reference, not a measured jaw or workpiece radius.
- The backlash output is exactly twice the entered radial allowance and is not a TIR prediction.
- Tooth geometry, jaw seating, manufacturing error, wear, deformation, force, friction, workpiece contact, actual gripping range, runout, capacity and safety are omitted.
Scroll Plate and Radial Jaws
U.S. Patent 224,119 documents jaws sliding radially in body grooves with rear teeth engaged by a spiral scroll, so rotating the scroll moves the jaws inward or outward. Later patents likewise describe a scroll plate or ring driving radially guided jaw bases in unison.
The animation shows that topology schematically. It does not reproduce a particular chuck's thread form, tooth engagement, jaw dimensions or usable range.
What This Calculator Represents
The tool treats entered pitch as ideal radial advance per scroll revolution. It adds signed pitch-times-turns travel to an entered mathematical origin and doubles signed radial travel for a diametral value. The final output merely doubles the entered radial backlash allowance.
Signed Archimedean-Scroll Travel
b = P/(2 pi)
r = a + b theta = a + PN
signed jaw travel = PN
signed diametral travel = 2PN
entered diametral backlash band = 2B
Worked Arithmetic Example
At entered origin 20 mm, pitch 4.5 mm/rev and +1 turn, computed signed coordinate is 24.5 mm, signed jaw travel is +4.5 mm and signed diametral travel is +9.0 mm. Entered radial backlash allowance 0.10 mm gives a direct 0.20 mm diametral band; it is not predicted TIR.
Model Boundary
- Calculated: ideal signed coordinate and pitch-times-turn travel.
- Illustrated: generic scroll plate and three equally spaced radial jaws.
- Not calculated: physical jaw position, gripping diameter, centering error, TIR, repeatability, tooth clearance distribution, jaw seating, wear, deformation, force, torque, friction, capacity, retention or safety.
Frequently Asked Questions
Is the computed coordinate an actual jaw radius?
No.
Does two times backlash equal TIR?
No; it is only a direct diametral presentation of the entered allowance.
Why can travel be negative?
Turns are signed; negative turns reverse the ideal travel direction.
What if the computed coordinate is negative?
That mathematical combination is outside a physical radial-coordinate interpretation.
Are all three real jaws guaranteed to move equally?
No; equal motion is the ideal scroll assumption.
Can this calculator select or inspect a chuck?
No.
References
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