Ball screws

HIWIN's FSI 16-5T3 has 5 mm/rev nominal lead. At an assumed 1,000 rev/min, nominal feed is 5,000 mm/min (5 m/min). The catalog lists 731 kgf dynamic and 1,331 kgf static axial rating. Lead gives motion scale, while support spacing, buckling, critical speed, preload and duty determine whether the complete drive can operate there. HIWIN, printed pp. 8–9 and 67.

Mechanism and construction

Recirculating balls roll between helical raceways to convert relative rotation into travel. HIWIN describes ground and precision-rolled grooves and heat-treated raceways. HIWIN, Ballscrew Technical Information, form S99TE22-2009, printed pp. 1–2 and 152.

HIWIN uses external return tubes, internal caps or endcap passages. Keep circuit count separate from screw starts. Nut and return geometry affect envelope, mounting and preload choices. HIWIN, printed pp. 7–9.

Lead, pitch and motion

Lead is axial travel per relative revolution. Pitch is axial spacing between adjacent threads. For a screw with z independent starts, lead = z × pitch; lead equals pitch only for a single start. A circuit-count suffix therefore cannot be substituted for the number of starts. Thomson, “What is the difference between screw pitch and lead?”.

For nominal lead l in mm/rev and relative rotational speed n in rev/min, the ideal kinematic relationship is v = l × n in mm/min. Thus a 5 mm/rev screw at 1,000 rev/min gives 5,000 mm/min = 5 m/min nominal feed. This is derived motion arithmetic, not a permissible-speed claim: lead error, compliance and temperature affect actual position, while shaft resonance and ball-return speed impose separate operating limits. Lead definition: Thomson; speed and thermal limits: HIWIN, printed pp. 31–34.

Load paths and supports

In a common rotating-screw arrangement, the nut is restrained against rotation by the moving table. Motor torque reaches the spindle through the drive connection; ball/raceway contact creates axial thrust at the nut. The table and its guides react the corresponding torque and guide the motion. Screw thrust passes through the axially locating support bearings and their housing into the machine structure. This is a mechanical interpretation of HIWIN's drive and support diagrams, not a statement that the motor bearings carry screw thrust. HIWIN, printed pp. 12 and 27; HIWIN, Support Unit Technical Information, B03TE03-1907, printed p. 3.

HIWIN's standard support drawing distinguishes angular-contact bearings at the fixed end from a deep-groove bearing at the supported end. The nut flange, bearing journals, shoulders, locknut and bearing housing are distinct interfaces. A nominal screw diameter does not specify any of those interfaces. Radial and moment loading arising from misaligned nut and bearing centers can reduce life; the screw/nut axial rating does not qualify the table's guiding system. Support catalog, printed pp. 2–3; ballscrew catalog, printed pp. 10–11.

Backlash, preload and stiffness

Clearance between balls and raceways permits axial play on load reversal. HIWIN describes preload from separated double nuts and a spacer, oversized balls in a single nut, or an offset within a single nut's raceway. Preload opposes clearance, but elastic deformation of balls, raceways, spindle and supports still produces displacement under changing load. A zero-clearance nut can therefore exhibit lost motion in an insufficiently stiff assembly. HIWIN, printed pp. 15 and 21.

Greater preload also increases drag torque and heat, affecting life and thermal positioning error. No universal preload percentage follows from the term “ball screw.” HIWIN's nut-stiffness tables and its general preloaded-nut discussion use different stated load conditions; the condition attached to the particular table governs that value. For the spindle and nut treated as axial springs in series, HIWIN writes 1/Kbs = 1/Ks + 1/Kn. Bearing and table-mount compliance further affect the complete feed system. This explains why a catalog nut stiffness is not assembly stiffness or positioning accuracy. HIWIN, printed pp. 2, 33–34 and 37.

A bounded catalog example: HIWIN FSI 16-5T3

The following values belong to FSI Type, Standard Product, model-size row 16-5T3, in form S99TE22-2009, printed p. 67 (PDF page 71). FSI denotes a flanged single nut with internal recirculation. This row identifies a nut/screw geometry and rating combination, not a complete ordered shaft with a chosen length, accuracy class, end machining or support assembly. HIWIN, printed pp. 8–9 and 67.

All dimensions and original force units above are from that row and its drawing/note. The nut's body drawing also shows a diameter portion with −0.1/−0.3 mm limits; that portion differs from the g6 locating portion. The hole labels refer to the section drawing, not a separate mounting instruction. The catalog bases its dimension-table dynamic/static ratings on HRC 60 surface hardness and gives correction factors for lower hardness. HIWIN, printed pp. 36 and 67.

Using standard gravity 1 kgf = 9.80665 N, the two ratings convert to approximately 7.169 kN and 13.053 kN, and K to 107.9 N/µm. These are derived unit conversions, not a second set of supplier ratings. The catalog's own buckling page uses the rounded conversion 1 kgf = 9.8 N, so rounded conversions can differ slightly. Shaft-end dimensions remain separate: for example, Table 3.2's fixed-side BK12 entry for 14–18 mm nominal shafts specifies a 12 mm D1 journal, 10 mm D2 end, E = 36 mm, M12 × 1 thread, and S = 12 mm. It does not establish the support spacing, bearing rating or completed end design for an installed FSI 16-5T3. HIWIN, printed pp. 10 and 31.

Ratings, life and operating limits

A dynamic load rating is a fatigue-life reference. HIWIN defines C at one million revolutions with 90% survival, and for its single-nut life equation uses L = (C/Fa)^3 × 10^6 revolutions. C and equivalent axial load Fa have the same force units; conversion to hours also needs average rotational speed. Variable loads need the catalog's load/speed weighting, and preload changes internal loading. The static rating concerns permanent raceway deformation, with HIWIN describing a 0.0001 × ball-diameter criterion. Neither rating is automatically an allowable continuous thrust, impact load or whole-machine safe working load. HIWIN, printed pp. 24–26 and 34.

Critical speed concerns rotating-shaft resonance; buckling concerns compressive instability. HIWIN's formulas depend on root diameter, effective length and end restraint; its Figure 4.27 demonstrates that buckling and critical-speed spans/restraints can differ in the same assembly. A longer unsupported length lowers both limits, independently of a nut's C rating. Dm-N limits instead concern ball pitch-circle diameter multiplied by rotational speed and the return system's operating behavior. The catalog contains special high-speed series, so its general Dm-N discussion is not a universal limit for every ball screw. HIWIN, printed pp. 31–33.

Accuracy, efficiency and application limits

Nominal lead gives motion scale. Lead accuracy describes deviation from intended travel; backlash describes reversal clearance; repeatability and stiffness describe other behavior. HIWIN treats ground and rolled lead-error definitions separately. Its rolled-screw table lists C7 cumulative lead variation over 300 mm as 50 µm, while ground-screw tables include travel-length-dependent quantities and variation over one revolution and 300 mm. A bare class label is consequently incomplete without its definition and product specification. These manufacturer tables are not evidence that the full ISO, JIS or DIN standards were read. HIWIN, printed pp. 14–15 and 152.

Rolling contact makes efficient, reversible transmission possible. HIWIN illustrates efficiency changing with lead angle and friction and includes different efficiencies in forward/reverse torque equations. Efficiency is not an accuracy class or a guaranteed constant for the FSI example. In a derived steady-state illustration, 1,000 N axial load, 5 mm/rev = 0.005 m/rev lead and an assumed 0.90 forward efficiency give T = F × l / (2π × η) ≈ 0.884 N·m. This omits bearing friction, preload drag, gearing and acceleration torque. Backdriving means an external axial load can generate rotation; the screw alone does not establish a vertical axis's holding or stopping capability. HIWIN, printed pp. 1–2 and 27.

Lubricant choice and replenishment depend on speed, load, temperature, contamination and the supplied assembly. Heat from friction changes spindle length and positioning behavior. No lubricant grade, service interval, installation torque, motor size or preload is prescribed here. The installed shaft length, end restraints, duty/load spectrum, accuracy definition, lubrication system and application validation remain customer-specific. Catalog dimensions and calculations do not establish qualification for an individual machine. HIWIN, printed pp. 14, 33–38.

Source editions and coverage

Sources were retrieved on 2026-10-31 PDT. The accessible HIWIN Ballscrew Technical Information PDF has 220 PDF pages, form S99TE22-2009, and an explicit ©2020 printed back-cover statement. Its Support Unit Technical Information PDF has 34 PDF pages, form B03TE03-1907, and an explicit ©2019 printed back-cover statement. No day/month publication date is printed in those statements; the form suffixes are retained as identifiers rather than decoded into dates. The web URL's /2026/08/ directory and PDF creation/modification metadata are not printed edition dates. Both catalogs state that specifications may change. Ballscrew back cover; support back cover.

The Thomson HTML tip has no displayed edition or publication date in the accessed text. HIWIN pages cited above were read as extracted text and rendered PDF pages; the sources establish manufacturer terminology and bounded catalog data, not current stock availability, interchangeability or customer performance. THK's attempted catalog download redirected to a login page; other THK/Thomson PDF endpoints were inaccessible, so their unverified catalog values are excluded. Full standards, installed machine measurements and customer qualification records were not accessed.

Related reference

Production planning references distinguishes a component reference from the configuration of a complete assembly.