Appearance
Skiving and roller burnishing is the only bore finishing process that cuts and compresses in a single pass — removing material with carbide blades, then immediately cold-working the surface to a mirror finish, all before the tool exits the tube.
Overview
Skiving and roller burnishing (SRB) was developed in the 1970s as a high-productivity alternative to honing for hydraulic cylinder tube finishing. The process uses a combined tool that performs two operations in sequence within a single pass through the tube:
- Skiving — carbide cutting blades remove a controlled thickness of material (0.2–1.0 mm per side) to correct bore geometry, straightness, and diameter
- Roller burnishing — hardened rollers immediately follow the skiving blades, cold-compressing surface peaks into valleys, creating a dense, work-hardened surface
The result is a bore that meets final tolerance and surface finish requirements in a fraction of the time required by honing. Modern SRB machines handle tube diameters from 30 mm to 600 mm and lengths up to 18 meters.
How SRB Works
Tool Construction
An SRB combined tool consists of two functional sections:
| Section | Component | Function |
|---|---|---|
| Front | Carbide cutting inserts (2–6 blades) | Removes material, corrects geometry |
| Middle | Chip evacuation gap | Allows chips to clear before burnishing |
| Rear | Hardened rollers (8–20) | Cold-works surface to final finish |
The tool is mounted on a hollow boring bar that connects to the machine's drive head. A rotary union provides hydraulic or pneumatic pressure through the rotating tool to expand and retract the skiving blades and burnishing rollers.
Tool Guidance
The SRB tool floats within the bore, following the existing hole axis. Nylon or carbide guide pads on the tool body contact the bore wall to maintain alignment without cutting. After the pass, the blades and rollers retract hydraulically, and the tool is withdrawn without contacting the finished surface.
Coolant Delivery
High-pressure coolant is delivered through the annular space between the boring bar and the tube wall. It cools the cutting edges, lubricates the burnishing rollers, and evacuates skiving chips through the tool center or the annular return path.
One-Way vs Two-Way Methods
One-Way Method (Single Pass)
Skiving and burnishing occur on the same forward stroke. The cutting inserts lead, followed immediately by the rollers.
| Aspect | Detail |
|---|---|
| Cycle | One forward pass, then rapid return |
| Advantages | Fastest cycle time, single positioning |
| Limitations | Must find common speed/feed for both operations |
| Typical | Medium to high volume, standard tolerances |
Two-Way Method (Dual Pass)
Skiving is performed on the forward stroke, then the rollers burnish on the return stroke.
| Aspect | Detail |
|---|---|
| Cycle | Forward skive, return burnish |
| Advantages | Independent parameter optimization for each operation; better surface finish |
| Limitations | Longer cycle time |
| Typical | High precision requirements, large diameters |
Method Selection
| Factor | One-Way | Two-Way |
|---|---|---|
| Cycle time | Faster | Slower |
| Surface finish | Good (Ra 0.2–0.4 µm) | Excellent (Ra 0.05–0.2 µm) |
| Tool complexity | Lower | Higher (retractable rollers) |
| Stock removal | 0.2–0.5 mm per side | 0.5–1.0 mm per side |
| Production volume | High | Medium to high |
Cutting Parameters
Skiving Parameters
| Parameter | Typical Range | Notes |
|---|---|---|
| Cutting speed | 150 – 300 m/min | Higher for steel, moderate for stainless |
| Feed rate | 1 – 6 mm/rev | Multiply by number of blades for effective feed |
| Depth of cut | 0.2 – 1.0 mm per side | Up to 3 mm per side on roughing passes |
| Surface after skive | Ra 4 – 10 µm | Intermediate, before burnishing |
Roller Burnishing Parameters
| Parameter | Typical Range | Notes |
|---|---|---|
| Roller speed | 80 – 200 m/min | Lower than skiving speed |
| Interference | 0.02 – 0.08 mm | Roller oversize relative to skived bore |
| Feed rate | 0.9 – 7.1 mm/rev | Partially self-feeding from roller contact |
| Coolant pressure | 10 – 25 bar | Sufficient for lubrication, not chip evacuation |
Combined Tool Parameters
For a typical 100 mm diameter steel hydraulic cylinder tube:
| Parameter | One-Way Value | Two-Way Value |
|---|---|---|
| Spindle speed | 500 rpm | 600 rpm (skive), 400 rpm (burnish) |
| Feed rate | 2 mm/rev (1,000 mm/min) | 3 mm/rev (1,800 mm/min skive), 2.5 mm/rev (1,000 mm/min burnish) |
| Depth of cut | 0.4 mm per side | 0.6 mm per side |
| Coolant flow | 300 L/min | 300 L/min |
| Cycle time (3 m tube) | ~3 min | ~5 min |
Feed rate is per revolution, not per blade
A tool with three skiving blades at 3 mm/rev removes 9 mm of advance per revolution across the three blades — each blade removes approximately 1.0 mm of material in the feed direction. Do not confuse tool feed rate with individual blade feed.
Achievable Quality
Dimensional
| Parameter | Typical | Best Practice |
|---|---|---|
| Diameter tolerance | IT8 | IT7 |
| Roundness | 0.036 mm per Ø200 mm | 0.020 mm per Ø200 mm |
| Cylindricity | 0.05 mm per 500 mm | 0.03 mm per 500 mm |
| Straightness | Follows existing bore | 0.1 mm per meter |
Surface
| Parameter | Typical | Best Practice |
|---|---|---|
| Surface finish (Ra) | 0.2 – 0.4 µm | 0.05 – 0.2 µm |
| Surface hardness increase | 30 – 50% | Up to 50% |
| Compressive residual stress | 200 – 600 MPa | Process-dependent |
| Fatigue life improvement | 200 – 300% | Compared to machined-only surface |
Material Effects
SRB produces a characteristic three-zone subsurface structure:
- Surface layer (1–5 µm) — heavily deformed, ultrafine grain structure from roller compression
- Deformed layer (20–100 µm) — elongated grains, high dislocation density from plastic deformation
- Transition zone (100–200 µm) — decreasing deformation to bulk material properties
The burnishing action eliminates surface micro-cracks and voids that may exist after skiving alone, producing a dense, near-defect-free surface.
Machine Requirements
Machine Platform
Most SRB machines are built on BTA-style deep hole drilling platforms. Approximately 80% of the machine design is shared with BTA drilling machines, with modifications for the SRB process:
| Component | SRB Requirement | Difference from BTA |
|---|---|---|
| Spindle power | 75 – 110 kW | Higher torque for burnishing |
| Spindle speed | 60 – 1,000 rpm | Stepless, wider range |
| Feed system | 5 – 5,000 mm/min | Higher feed capability |
| Coolant pump | 10 – 25 bar, 300–700 L/min | Lower pressure, higher flow than drilling |
| Rotary union | Hydraulic/pneumatic pass-through | Required for blade/roller actuation |
Workholding
SRB machines use specialized workholding to avoid deforming thin-walled tubes:
- Clamping cones — grip tube ends without distorting the bore
- Hydraulic V-blocks — support the tube along its length without marking the OD
- Steady rests — prevent tube sag during the pass
Material Starting Conditions
| Starting Material | Preparation Needed | Typical Stock Removal |
|---|---|---|
| Cold-drawn seamless tube | None (direct SRB) | 0.2 – 0.5 mm per side |
| Hot-rolled seamless tube | Counter-boring or rough skive | 0.5 – 3.0 mm per side |
| BTA-drilled bore | None (direct SRB) | 0.3 – 0.8 mm per side |
SRB vs Honing
Cycle Time
| Tube Length | SRB Cycle Time | Honing Cycle Time | Savings |
|---|---|---|---|
| 1 m | 1 – 2 min | 15 – 30 min | 90%+ |
| 3 m | 3 – 5 min | 45 – 90 min | 90%+ |
| 6 m | 6 – 10 min | 90 – 180 min | 90%+ |
SRB is 8–20 times faster than conventional honing because it is a single-pass process. Honing requires multiple passes with progressively finer stones, each pass requiring reciprocation along the full tube length.
Surface Characteristics
| Attribute | SRB | Honing |
|---|---|---|
| Ra achievable | 0.05 – 0.4 µm | 0.05 – 0.4 µm |
| Surface hardness | Increased 30–50% | Unchanged |
| Residual stress | Compressive (beneficial) | Neutral or tensile |
| Oil retention | Low (mirror surface) | Good (crosshatch pattern) |
| Fatigue life | Improved 200–300% | Unchanged |
| Seal compatibility | Excellent for PTFE and polyurethane | Excellent with crosshatch |
Economic Comparison
| Factor | SRB | Honing |
|---|---|---|
| Machine investment | Higher | Lower |
| Tooling cost per part | Lower at volume | Higher (abrasive stones) |
| Cycle time per part | 1–5 minutes | 15–180 minutes |
| Labor cost per part | Significantly lower | Higher |
| Consumables | Carbide inserts | Abrasive stones, oil |
| Setup time per diameter | Tool change | Stone adjustment |
| Per-part cost at volume | Lower | Higher |
SRB is not a direct honing replacement for all applications
SRB replaces honing effectively for production hydraulic cylinder tubes where surface finish and tolerance requirements are within IT7–IT8 and Ra ≥ 0.05 µm. However, when a specific crosshatch angle is required for oil retention, or when tolerances below IT7 are needed, honing remains the appropriate process. Evaluate the seal manufacturer's surface specification before switching.
Common Applications
| Industry | Component | Diameter Range | Length |
|---|---|---|---|
| Construction equipment | Hydraulic cylinders | 50 – 200 mm | 1 – 6 m |
| Agricultural machinery | Lift cylinders, steering cylinders | 40 – 150 mm | 0.5 – 3 m |
| Mining | Heavy-duty cylinder tubes | 100 – 300 mm | 2 – 8 m |
| Material handling | Telescopic cylinders | 60 – 250 mm | 3 – 12 m |
| Oil and gas | Wellhead control cylinders | 75 – 200 mm | 1 – 4 m |
| Marine | Steering cylinders, stabilizers | 100 – 400 mm | 2 – 8 m |
Summary
| Aspect | SRB | Honing |
|---|---|---|
| Cycle time | 1–5 minutes per tube | 15–180 minutes per tube |
| Tolerance | IT7–IT8 | IT5–IT6 |
| Surface finish (Ra) | 0.05 – 0.4 µm | 0.05 – 0.4 µm |
| Surface hardness | +30–50% | No change |
| Fatigue life | +200–300% | No improvement |
| Oil retention | Low | Good (crosshatch) |
| Best for | High-volume production | Precision, low-volume, repair |
FAQ
What is the difference between skiving and roller burnishing?
Skiving is a cutting operation — carbide blades remove material from the bore surface to correct geometry, diameter, and straightness. Roller burnishing is a cold-working operation — hardened rollers compress the surface peaks into valleys, creating a smooth, work-hardened finish without removing additional material. In SRB, both operations are performed sequentially within a single pass.
How fast is skiving and roller burnishing compared to honing?
SRB is 8–20 times faster than conventional honing. A 3-meter hydraulic cylinder tube that takes 45–90 minutes to hone can be skived and roller burnished in 3–5 minutes. The speed advantage comes from SRB being a single-pass process — the tool cuts and finishes the bore in one pass, while honing requires multiple reciprocating passes with progressively finer stones.
What tolerances can skiving and roller burnishing achieve?
SRB typically achieves IT7–IT8 diameter tolerance, with roundness of 0.036 mm per Ø200 mm and cylindricity of 0.05 mm per 500 mm. Surface finish of Ra 0.05–0.4 µm is standard. Best practice conditions can achieve IT7 with Ra 0.05–0.2 µm. The process also increases surface hardness by 30–50% and introduces beneficial compressive residual stress.
What materials can be skived and roller burnished?
SRB is primarily used on steel hydraulic cylinder tubes: carbon steels (1045, 1026), alloy steels (4140, 4130), stainless steels (304, 316), and ductile iron. The process works best on materials with good plastic deformation characteristics. Cast iron and some powder metal materials may not respond well to burnishing due to their porosity and limited ductility.
Is SRB suitable for thin-walled tubes?
Yes, but workholding is critical. SRB machines use clamping cones and hydraulic V-blocks to support thin-walled tubes without distortion. The burnishing forces are radial inward, which can collapse unsupported thin tubes if the workholding is inadequate. For very thin walls (wall thickness < 5% of diameter), honing may be safer because the cutting forces are lower.
When should I choose honing over skiving and roller burnishing?
Choose honing when: the application requires a specific crosshatch angle for oil retention below Ra 0.1 µm, tolerances tighter than IT7 are needed, the part requires repair or oversize reconditioning, production volume is low (tooling setup cost cannot be amortized), or the customer specification explicitly requires a honed crosshatch surface. For all other hydraulic cylinder production, SRB is faster and more economical.
Skiving and roller burnishing process capabilities depend on machine configuration, tooling design, workpiece material, and tube dimensions. The values in this article are typical ranges for production applications. Consult machine builders and tool suppliers for application-specific process recommendations. This article reflects industry knowledge as of 2026.