A full-rotary lockstitch hook rotates continuously around a stationary bobbin holder and catches the needle-thread loop. In the selected ideal 2:1 drive, the hook makes two revolutions per stitch cycle; this calculator converts selected stitch-cycle rates and hook-circle diameter into hook-tip speed.
Full-Rotary Sewing Hook Ideal Speed Reference
Compare exact ideal hook speed and hook-tip speed for a selected full-rotary 2:1 drive.
Equation Used
- The selected topology is a continuously rotating full-rotary hook.
- The hook makes exactly two revolutions per stitch cycle.
- The selected diameter is the circular hook-tip path diameter.
- Slip, dynamics, thread interaction, ratings, wear, heat and safety are excluded.
Low, nominal and high are independent selected comparison rates, not operating recommendations.
Ideal full-rotary-hook drive
Historical rotary-hook patents describe a two-to-one hook/main-shaft ratio, while JUKI identifies the DDL-8700 as using an automatic-lubricating full-rotary hook. The animation closes a crank–rod–guided-needle chain and meshes 2:1 pitch circles driving the hook reference.
The thread loop, bobbin thread, take-up and feed timing are intentionally not reconstructed.
What the calculator determines
Select hook-circle diameter and three independent stitch-cycle rates. For each selected rate N, the ideal hook speed is 2N rpm and hook-tip speed is πD(2N/60).
The labels low, nominal and high are comparison labels, not operating recommendations.
Ideal speed identities
nhook = 2N and vtip = πD nhook/60, with D converted from millimetres to metres.
Selected-input arithmetic
For D = 26 mm and N = 4,500 cycles/min, ideal hook speed is 9,000 rpm and hook-tip speed is about 12.25 m/s.
Intentionally partial mechanism
This exact kinematic speed conversion is limited to a full-rotary hook with the selected 2:1 ratio. It does not apply to every shuttle or oscillating hook and does not model thread-loop capture, bobbin-case geometry, lubrication, vibration, wear, balance, heat, loads, permissible machine speed, stitch quality or safety.
Questions
Does every sewing shuttle rotate at 2N?
No; this reference is explicitly for the selected full-rotary topology.
Are the three rates machine ratings?
No.
Does tip speed validate stitch formation?
No.
References & Further Reading
- Wikipedia contributors. Sewing machine. Wikipedia
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