Skiving & Roller Burnishing: Eliminating Secondary Honing

Honing a hydraulic cylinder tube to Ra 0.2 µm takes minutes and consumes abrasive stones. Skiving and roller burnishing the same tube to Ra 0.1 µm takes seconds, work-hardens the surface, and creates no abrasive sludge. The question is not whether SRB is better — it is why anyone still hones.

Skiving and roller burnishing (SRB) is the highest-productivity bore finishing process for hydraulic and pneumatic cylinder tubes. By combining a cutting operation (skiving) with a cold-working operation (roller burnishing) in a single pass, it achieves surface finishes and tolerances that rival honing at a fraction of the cycle time.

How SRB Works ​

Process Principle ​

SRB uses a combined tool head that performs two operations:

Skiving: A carbide cutting edge removes a controlled thickness of material (typically 0.2–0.5 mm on diameter) to size the bore, correct ovality, and remove surface defects from the previous operation (cold drawing, rough drilling, or tube manufacturing).

Roller burnishing: Hardened rollers (typically 3–6 rollers arranged circumferentially) cold-work the skived surface. The rollers press against the bore wall under controlled pressure, plastically deforming surface peaks into valleys. This eliminates the feed marks left by skiving and creates a mirror-like surface.

One-Way vs. Two-Way Configurations ​

In the one-way method, the skiving inserts and burnishing rollers are arranged on the same tool body. Both contact the bore simultaneously during the forward pass. The tool then quick-retracts. This provides the shortest cycle time but requires the tools to share feed and speed parameters.

In the two-way method, skiving is performed on the forward stroke. At the end of the stroke, the burnishing section engages, and the tool finishes the surface on the return stroke. This allows independent optimisation of cutting and burnishing parameters.

Capabilities ​

Surface Finish ​

SRB produces a measurably smoother surface than honing in most production applications, though the best honed finishes (Ra 0.05 µm) are slightly finer than the best SRB finishes (Ra 0.05–0.10 µm). The key difference is surface character: SRB produces a mirror-like, isotropic surface, while honing leaves a crosshatch pattern.

Tolerance and Geometry ​

Honing can achieve tighter geometric tolerances, particularly in roundness and cylindricity, because the abrasive stones self-centre and follow the existing bore geometry. SRB's geometric accuracy depends more on the machine tool's alignment and the workpiece's wall thickness.

Work Hardening and Fatigue Life ​

Roller burnishing cold-works the bore surface, producing a layer of compressive residual stress:

This work-hardened layer is unique to roller burnishing among bore finishing processes. Honing removes material without altering the subsurface, while grinding can leave harmful tensile residual stresses.

Cycle Time Comparison ​

The cycle time advantage of SRB over honing is the process's most compelling economic benefit.

Quantitative Comparison ​

For a typical hydraulic cylinder tube (100 mm bore × 2,000 mm length):

Sources consistently report cycle time reductions of 60–90% for SRB compared to honing:

Tip: The cycle time advantage of SRB is largest for long tubes (2 m+) and large diameters (100 mm+). For short tubes (<500 mm) with small diameters (<40 mm), the time difference narrows because setup time dominates both processes.

Tooling Systems ​

Types of SRB Tools ​

Key Manufacturers ​

SRB Machine Configurations ​

Cost Analysis ​

Per-Metre Tool Cost ​

Capital Equipment ​

SRB machines have higher initial cost than equivalent honing machines, but the lower per-part tool cost and higher throughput typically result in a lower total cost per metre of finished tube at production volumes above 1,000 m per year.

Breakeven Analysis ​

For a shop producing hydraulic cylinder tubes (100 mm bore × 2 m length):

When to Choose SRB vs. Honing ​

Choose SRB When ​

• Production volume exceeds 2,000 tubes per year
• Tube length exceeds 1 metre
• Surface finish requirement is Ra ≤ 0.4 µm
• Work-hardened surface would benefit the application (high-pressure cylinders, fatigue-loaded components)
• Cycle time reduction justifies capital investment
• Clean chip recycling is a priority (no abrasive sludge)

Choose Honing When ​

• Production volume is below 500 tubes per year
• Tightest geometric tolerances (roundness < 5 µm, cylindricity < 5 µm) are required
• Crosshatch oil-retention surface is required for the application
• Tube wall thickness is thin relative to diameter (t/ID < 0.1) — SRB risks ovality
• Repair or rework of existing bores
• Material is not conducive to burnishing (cast irons, powder metals)

Warning: SRB is not a drop-in replacement for honing. The mirror-like SRB surface does not retain oil the way a honed crosshatch does. For hydraulic cylinders that rely on oil retention between the piston seal and bore wall, the SRB surface may increase seal wear or require a different seal material. Test before switching from honing to SRB for existing cylinder designs.

Integration with Deep Hole Drilling ​

SRB is often combined with deep hole drilling as part of a complete bore manufacturing process chain.

Complete Process Chain for Hydraulic Cylinders ​

1. BTA drilling or gun drilling: Creates the initial bore from solid bar or tube
2. Trepanning (optional): For very large diameters, removes a core that can be repurposed
3. Skiving and roller burnishing: Single-pass finishing of the bore to final size and surface finish
4. Inspection: Air gaging or CMM verification of bore diameter, roundness, and surface finish

Sunnen's SHD series, developed after the BTA Heller acquisition, integrates drilling, skiving, roller burnishing, and honing in a single machine platform. This drill-to-finish bore solution is the most complete example of process integration in the deep hole drilling and finishing industry.

FAQ ​

What is the difference between skiving and roller burnishing? ​

Skiving is a cutting operation — a carbide tool removes a thin layer of material to size the bore and correct geometry. Roller burnishing is a cold-forming operation — hardened rollers press against the bore surface, plastically deforming peaks into valleys to create a mirror finish. Skiving removes material; burnishing displaces it.

How much faster is SRB than honing? ​

SRB is 60–90% faster than honing, depending on the tube dimensions and surface finish requirements. The time saving comes from two factors: SRB completes the bore in a single pass (vs. 3–6 passes for honing), and the skiving feed rate (1–4 mm/rev) is 3–10× higher than honing feed rates (0.1–0.5 mm/rev).

Can SRB replace honing for all hydraulic cylinder tubes? ​

No. SRB is optimal for high-volume production of thick-walled tubes where the surface finish requirement is Ra ≤ 0.4 µm. Honing remains superior for thin-walled tubes (where SRB's roller pressure can cause ovality), for applications requiring a crosshatch oil-retention pattern, and for the tightest geometric tolerances (roundness < 5 µm).

What surface finish can SRB achieve? ​

SRB typically achieves Ra 0.05–0.20 µm (mirror finish). The skiving pass alone produces Ra 4–10 µm, which is then burnished to the final finish. The best SRB finishes (Ra 0.05 µm) are comparable to fine honing, though the surface character differs — mirror-like vs. crosshatch.

Does roller burnishing increase surface hardness? ​

Yes, significantly. Roller burnishing cold-works the bore surface, increasing hardness by 30–50% in steel. This work-hardened layer also contains compressive residual stress, which improves fatigue life by up to 300% compared to a honed or ground surface without cold working.

What is the cost difference between SRB and honing equipment? ​

SRB machines have a higher initial cost — typically 20–40% more than equivalent honing machines. However, the per-metre tool cost is lower (less frequent tool changes, no abrasive stones), and the cycle time reduction of 60–90% means fewer machines are needed for the same production volume. The breakeven point is typically 2,000–5,000 tubes per year.

What manufacturers offer SRB tooling and machines? ​

Sunnen (SHD series with BTA Heller tooling), Sugino (Skive Roller vertical machines), Ecoroll (Omega system), Cogsdill (skive burnishing tools), Yamasa CEOS (combined tools), and Sandvik Coromant (indexable insert SRB tooling) are the major suppliers. Sunnen's SHD series is notable for integrating drilling, skiving, burnishing, and honing in one platform.

How does the SRB surface affect hydraulic cylinder seal life? ​

The mirror-like SRB surface reduces seal wear compared to a honed surface because there are no asperities to abrade the seal lip over time. However, the SRB surface does not retain oil the way a honed crosshatch surface does. For cylinders that rely on oil retention between strokes, seal material selection must account for the different surface character. PTFE and polyurethane seals generally perform well on SRB surfaces.

Summary ​