Hardened Linear
Guide Shafts

A guide shaft (linear guide rod) is a precision-ground cylindrical shaft on which a linear bushing or ball spline nut runs. The guide shaft defines the line of motion for the carriage, tool, or workpiece. Critical parameters: OD tolerance (h6/f7 depending on bushing fit class), hardness (HRC 58–62 to resist bushing ball wear), surface finish (Ra 0.2 µm to minimise friction and wear), and straightness (≤ 0.005 mm/300 mm).

Standard ISO linear bushing systems use a shaft tolerance of h6 for most applications — a slight clearance fit with the bushing bore (typically H7). For higher precision or closer preload: h5. For sliding plain bushings requiring controlled clearance: f7. Always check the linear bushing manufacturer's (INA, THK, NSK, HIWIN, PMI) recommended shaft tolerance — it varies by bushing series.

Linear bushing balls roll on the guide shaft surface under Hertzian contact pressure. If the shaft surface is too soft (below HRC 58), the balls indent the shaft, rapidly increasing clearance and causing slop. Standard recommendation: HRC 58–62 minimum for steel guide shafts with steel-ball linear bushings. Softer materials (aluminium, stainless) require polymer or PTFE-lined bushings — the bushing manufacturer specifies minimum shaft hardness.

Yes — HXC standard guide shaft supply includes end machining: ground end faces, threaded ends (M5–M24 or UNC/UNF), shoulder steps for end-stop features, and tapped mounting holes in the shaft end face. All end features are machined in the same setup as OD grinding, ensuring perpendicularity of end faces to shaft axis within 0.005 mm.

Prototype (1–5 pcs, turned + ground): 4–7 days. Small batch (10–50 pcs): 7–12 days. Production (100–1,000 pcs): 10–16 days. Hard chrome plating: add 2–4 days. Stainless or titanium: add 2–4 days. Rush production available.

GCr15 (SUJ2) bearing steel HRC 60–62 — the standard for ball-bushing rails. 42CrMo4 induction hardened — CNC and router axes. SUS440C hardenable stainless — corrosion / clean-room. Hard-chrome plated C45 — long-stroke rods. Al 7075 hard-anodized — lightweight axes with polymer bushings.

Standard ground OD: Ra 0.4 µm. Linear bushing running surface (HXC default): Ra 0.2 µm. Mirror finish for low-friction plain bushings: Ra 0.1 µm. All measured by contact profilometer and reported on the inspection certificate.

Standard straightness for ground guide rods: ≤ 0.005 mm per 300 mm of length. For precision stages: ≤ 0.003 mm per 300 mm on request. Long rods (over 1 m) are straightened and stress-relieved before final grinding to hold straightness. Straightness is measured on a granite surface plate with the rod rotated in vee-blocks.

Yes — threaded ends, shoulder steps, flats, cross-holes, tapped end holes, and circlip grooves are all machined in the same setup as OD grinding, ensuring concentricity and perpendicularity within 0.005 mm. Specify end configuration on the drawing.