Indexing-Grade Ground
Rotary Table Shafts

A rotary table shaft (indexing table spindle) is the central rotating element of a rotary table, 4th-axis, or 5-axis trunnion. It must provide precise rotational motion while maintaining axial and radial runout to ≤ 0.002 mm — any runout here directly adds to machining error on every part processed on the table. The shaft typically includes a taper bore (BT30/40/50, ISO, or HSK) for workholding, a worm gear or direct-drive interface, and precision bearing journals.

For a CNC 4th-axis machining centre rotary table: radial runout ≤ 0.002 mm (measured at the taper gauge line); axial runout ≤ 0.002 mm (measured at the face); face flatness ≤ 0.003 mm (workpiece contact face). For a precision CMM rotary table: radial and axial runout ≤ 0.001 mm. For a production fixture rotary table: ≤ 0.005 mm is acceptable. HXC measures and reports all three on every rotary table shaft.

A Hirth coupling (serrated coupling) is a precision indexing joint with triangular radial serrations that engage mating teeth — providing highly repeatable angular positioning (typically ±1 arc-second) with no backlash. Rotary table shafts with Hirth coupling flanges are used in 5-axis machine tool trunnion assemblies and precision inspection equipment. HXC machines Hirth coupling flanges on rotary table shafts to DIN ISO 4156 serration standards.

Standard taper bores for rotary table shafts: BT30, BT40, BT50 (JIS B 6339 metric taper); ISO 30, 40, 50 (DIN 2080); CAT40, CAT50 (ANSI B5.50). HXC grinds taper bores to IT4 tolerance using precision taper grinding, with surface finish Ra 0.4 µm and taper gauge contact ≥ 75% on a blue-check gauge. Specify the spindle taper standard and machine interface on your drawing.

Prototype (1–5 pcs, hardened + ground + lapped): 6–9 days. Small batch (10–50 pcs): 9–14 days. Production (100–500 pcs): 12–18 days. Hirth coupling adds 2–4 days. Stainless or titanium: add 2–4 days. Rush production available.

42CrMo4 (induction hardened to HRC 52–58) — standard for CNC 4th-axis and trunnion shafts. 20CrMnTi (carburized to HRC 60+) — heavy-load trunnion and indexing tables. GCr15 (SUJ2) through-hardened bearing steel — CMM rotary tables requiring < 0.001 mm runout. SUS440C hardenable stainless — clean-room and semiconductor wafer rotation. Ti Grade 5 — aerospace fixture spindles.

Bearing journals: Ra 0.4 µm standard, Ra 0.2 µm on request. Taper bore: Ra 0.4 µm with ≥ 75% blue-check contact. Workholding face: Ra 0.4 µm and flatness ≤ 0.003 mm. CMM rotary spindles: mirror finish Ra 0.1 µm available. All measured by contact profilometer and reported.

Yes — HXC machines worm wheel teeth integral to the rotary table shaft (single-piece construction) in 5-axis turn-mill cells. This eliminates the runout error of a separately bolted worm wheel. AGMA 10–12 worm wheel accuracy class achievable. Specify worm wheel pitch, module, and pressure angle on the drawing.

Yes — Hirth coupling flanges to DIN ISO 4156 (typical 72-tooth or 96-tooth serration) are machined on the rotary table shaft as integral features. Tooth angle is ground after heat treatment for ±1 arc-second indexing repeatability. Larger or non-standard tooth counts available on request.