# Three-jaw scroll chucks Synchronized manual chuck jaws, centering limits, jaw configurations, mounting and the distinction between static gripping force and rotating conditions. Reviewed: 2026-11-02 Tags: tooling, workholding, turning Kitagawa lists **9.0 kN maximum static gripping force** and **29.4 N·m permissible handle torque** for its **SC-3N** rotary-table scroll chuck. Static force and input torque describe different quantities. At speed, jaw mass and radius change centrifugal loading, and a repeatable scroll can still center the part off the spindle axis. [Kitagawa manual, pp. 10, 12](https://www.kitagawa.com/en/mtools/inc/data/PDF/manu_SC-N_JN-N_en.pdf). Use [Choosing workholding](../workholding-and-fixtures.md) to compare location, support and restraint across fixture types. ## Mechanism and purpose A common scroll moves three jaws together to grip round or hexagonal stock. Sherline describes a knurled ring driving its small manual chucks. [Sherline chuck overview](https://www.sherline.com/chucks/) Kitagawa SC-(F)N/JN-(T)N rotary-table chucks use a handle and three pinions. The powered HRS08 uses hydraulic cylinder thrust, a wedge plunger and wedge hooks at the master jaws. [Kitagawa scroll manual, pp. 2, 7](https://www.kitagawa.com/en/mtools/inc/data/PDF/manu_SC-N_JN-N_en.pdf), [Kitagawa HRS08 manual, p. 4](https://www.kitagawa.com/en/mtools/inc/data/PDF/manu_HRS_en/manu_HRS_en.pdf) ## Centering is different from repeatability Centering error is the displacement of the held feature's axis from the spindle axis. Repeatability concerns how closely repeated clampings reproduce a position. A chuck can repeat a consistent offset; neither synchronized motion nor repeated readings proves zero offset. This distinction is explanatory synthesis rather than a quoted chuck specification. For an ideal circular surface with pure parallel-axis eccentricity e, an indicator's total indicated runout is **TIR = 2e**. An original example with e = 0.020 mm therefore gives **0.040 mm TIR**. Actual readings can also include roundness error, tilt and spindle or mounting effects, so half the reading is not always the axis offset. Sherline states less than 0.003 inch runout for its referenced chucks and notes a maximum rotation speed of 3,000 rpm for their designed tolerances. Those are Sherline-specific statements, not a universal scroll-chuck accuracy class or speed rating. [Sherline accuracy and speed scope](https://www.sherline.com/chucks/) ## Gripping range and jaw configuration A chuck's body diameter, through bore and gripping range are separate dimensions. For example, Bison's 3204-4 inch product has a 100 mm body size and 20 mm through hole, plain-back mounting and solid hard jaws. Its spare-parts listing distinguishes inside and outside solid jaw sets. A 100 mm chuck is therefore neither a 100 mm through bore nor proof that every 100 mm workpiece is supported. [Bison 3204-4 inch](https://bison-america.com/produkt-25905-3204.html) Some jaws are reversible; others require a different set. Sherline's P/N 1040 normally grips stock up to 38 mm diameter and uses reversed jaws for larger work. Its jaw engagement order and slot assignment matter after reversal. These instructions apply to that design, not to every solid jaw. [Sherline jaw operation instructions](https://sherline.com/wp-content/uploads/2014/07/5326_instructions_v9_web.pdf) Kitagawa supplies separate internal and external jaw sets with its SC/JN front-mount series and explicitly excludes soft jaws on JN models. Its JN06-101 table lists external gripping of 3–160 mm and internal gripping of 48–150 mm. These ranges describe the named configuration; they are not interchangeable with the adjacent JN06T102 two-piece-jaw configuration. [Kitagawa front-mount scroll chucks](https://www.kitagawa.com/en/mtools/csc/front_mounting_type_scroll_chucksc_jn_jn-t_series.html) ## Mounting, force and rotation Mounting is an interface requirement rather than a consequence of jaw count: the Bison example uses a plain back, while Sherline's normal small-machine mounting uses a 3/4-16 internal thread. Register fit, attachment geometry and the compatible spindle or rotary table remain separate from gripping diameter. [Bison mounting](https://bison-america.com/produkt-25905-3204.html), [Sherline spindle interfaces](https://www.sherline.com/chucks/) Kitagawa's rotary-table scroll manual, version 1.12 dated **May 7, 2026**, distinguishes maximum static gripping force from permissible handle torque. For SC-3N these are 9.0 kN and 29.4 N·m. Its gripping-range limits protect jaw-to-scroll engagement; excessive torque and taller-than-standard jaws are outside its stated use. These rotary-table models do not establish lathe operating limits. [Kitagawa manual, pp. 10, 12](https://www.kitagawa.com/en/mtools/inc/data/PDF/manu_SC-N_JN-N_en.pdf) Static force is measured without rotational centrifugal effects. Bison's manual-chuck technical data makes maximum speed conditional on standard jaws remaining within the chuck outside diameter, good chuck/jaw condition and specified balance; it also identifies workpiece mass and cutting conditions as relevant. A catalog maximum rpm is consequently not a guarantee of unchanged gripping force or suitability for a particular workpiece. [Bison manual-chuck technical data, p. 121](https://www.bison-america.com/downloads/Bison%20Manual%20Chucks%202022.pdf0dc7b703662eef7498680a857981e086.pdf) **Original force illustration:** an assumed 0.25 kg jaw with its center of mass 0.075 m from the axis at 2,000 rpm has outward centrifugal force m r (2πn/60)² ≈ **822 N**. At 4,000 rpm it becomes approximately **3,290 N**. Doubling speed quadruples this force. These assumed values do not rate a chuck or calculate its residual grip; jaw restraint and the complete mechanism also matter. ## Coverage limits This reference covers manual workholding scroll chucks, including named rotary-table examples. It provides no universal repeatability, permissible jaw projection, gripping torque or rpm. The cited web pages establish no verified issue dates; the date embedded in the Bison download name is not treated as a printed edition date. Workpiece geometry, jaw condition, mounting and cutting loads determine applicability of each product's limits.