Appearance
A skiving tool with a 5° negative rake angle and 0.2 mm depth of cut removes a continuous ribbon of material from a deep drilled bore at feed rates up to 2 m/min — producing a surface finish of Ra 0.3–0.6 µm that requires only roller burnishing to reach hydraulic cylinder quality. The efficiency of skiving compared to honing is dramatic: skiving can remove 0.5 mm of stock from a 2-meter bore in under one minute, while achieving the same diameter reduction by honing would require 5–15 minutes. The key to successful skiving lies in the tool geometry — the rake angles, edge preparation, guide pad configuration, and chip breaker design that together create a stable, chatter-free cutting action over the full bore length.
Skiving Tool Geometry
Cutting Edge Geometry Parameters
| Parameter | Typical Range | Effect on Cutting Action | Effect on Surface Finish |
|---|---|---|---|
| Radial rake angle | −5° to −10° | Negative rake strengthens edge — increases cutting force | Positive: reduces vibration — slight increase in roughness |
| Axial rake angle | 0° to −5° | Controls chip flow direction | Significant: influences helical feed marks |
| End cutting edge angle | 45–60° | Controls chip thickness and cutting edge engagement | Moderate: affects peak-to-valley height |
| Side cutting edge angle | 2–8° | Distributes wear — controls radial force | Moderate: affects bore taper tendency |
| Clearance angle (primary) | 5–8° | Prevents flank rubbing — reduces heat | Low: sufficient clearance prevents surface damage |
| Clearance angle (secondary) | 10–15° | Provides additional relief behind primary | Low: prevents heel contact |
Skiving Insert Options
| Insert Type | Grade Recommendation | Coating | Edge Preparation | Depth of Cut Range | Best Material Application |
|---|---|---|---|---|---|
| CBN-tipped | PCBN (50–70% CBN) | None (CBN is coating) | 0.05–0.15 mm chamfer | 0.1–0.4 mm | Hardened steel — heat-treated alloys |
| Coated carbide P20–P30 | Fine-grain carbide | TiAlN + Al₂O₃ multilayer | 0.08–0.20 mm T-land + hone | 0.2–0.5 mm | Medium-carbon steel — alloy steel |
| Coated carbide K10–K20 | Sub-micrograin carbide | AlTiN or Al₂O₃ | 0.05–0.10 mm hone | 0.15–0.4 mm | Cast iron — ductile iron |
| Uncoated carbide | Ultra-fine grain | None | 0.03–0.08 mm hone | 0.1–0.3 mm | Aluminum — non-ferrous |
| PCD-tipped | Polycrystalline diamond | None | 0.02–0.05 mm hone | 0.1–0.3 mm | High-silicon aluminum — composites |
Skiving Parameters and Performance
Recommended Cutting Parameters by Material
| Workpiece Material | Cutting Speed (m/min) | Feed Rate (mm/rev) | Depth of Cut (mm) | Expected Ra (µm) | Tool Material |
|---|---|---|---|---|---|
| Low-carbon steel (1018, 1020) | 120–180 | 0.8–2.0 | 0.2–0.5 | 0.3–0.6 | Coated carbide — P20–P30 |
| Medium-carbon steel (1045) | 100–160 | 0.6–1.5 | 0.2–0.4 | 0.3–0.6 | Coated carbide — P20–P30 |
| Alloy steel (4140, 4340) annealed | 80–140 | 0.5–1.2 | 0.2–0.4 | 0.3–0.6 | Coated carbide — P20–P30 |
| Alloy steel hardened (35–45 HRC) | 60–100 | 0.4–0.8 | 0.1–0.3 | 0.2–0.5 | CBN-tipped |
| Stainless steel (304, 316) | 80–120 | 0.4–1.0 | 0.15–0.35 | 0.4–0.8 | Coated carbide — M15–M25 |
| Gray cast iron | 120–200 | 1.0–2.5 | 0.3–0.6 | 0.3–0.6 | Coated carbide — K10–K20 |
| Ductile iron | 100–160 | 0.8–2.0 | 0.2–0.5 | 0.3–0.6 | Coated carbide — K10–K20 |
| Aluminum (6061, 7075) | 200–400 | 0.8–2.0 | 0.2–0.5 | 0.2–0.5 | PCD — uncoated fine-grain carbide |
FAQ
How does skiving differ from conventional boring?
Skiving differs from conventional boring in several fundamental ways. Skiving uses multiple cutting edges (typically 3–8) arranged around the tool circumference, while boring typically uses a single point tool or two opposing cutters. Skiving operates at higher feed rates (0.5–2.5 mm/rev compared to 0.1–0.3 mm/rev for boring) and removes stock in a thin ribbon rather than producing segmented chips. The skiving tool incorporates guide pads that maintain alignment within the existing bore — the tool follows the existing hole axis rather than being entirely dependent on machine alignment. The cutting action in skiving produces a characteristic surface finish with feed marks that are typically 0.3–0.6 µm Ra, while boring typically produces 0.8–3.2 µm Ra. Skiving is specifically designed as a finishing operation for previously drilled or rough-machined bores and cannot correct significant hole position errors.
What is the correct rake angle for skiving tools?
Skiving tools use negative radial rake angles of −5° to −10°, which is fundamentally different from conventional turning tools that typically use positive rake angles. The negative rake strengthens the cutting edge to withstand the interrupted cutting action as each insert enters and exits the cut, and it directs cutting forces into the tool body rather than into the cutting edge. The negative rake also produces a controlled chip flow that helps manage the long, continuous ribbon chips characteristic of skiving. Axial rake angles are typically 0° to −5°, designed to direct chips ahead of the tool rather than wrapping around the tool body. The specific rake angle within this range is selected based on the workpiece material — softer materials use less negative rake (−5°), while harder materials use more negative rake (−8° to −10°) for additional edge strength.
How are guide pads configured on skiving tools?
Guide pads on skiving tools are critical for maintaining tool alignment within the bore. Typical skiving tool designs use 3–6 guide pads arranged around the tool circumference, positioned between the cutting inserts. The pads are made from carbide or PCD and are slightly smaller in diameter than the cutting inserts (by 0.02–0.05 mm per side) to prevent the pads from contacting the bore surface before the cutting edges. The pads engage the freshly cut surface immediately behind the cutting edges, providing continuous support that prevents tool deflection and chatter. The pad length is typically 1.5–3 times the tool diameter, and the pad width is 3–8 mm depending on tool size. Adjustable pads allow diameter compensation for wear and fine-tuning of the bore diameter. Pad clearance must be carefully controlled — excessive clearance allows tool vibration, while insufficient clearance causes overheating and surface damage.
What surface finish can be expected from skiving?
Skiving typically produces a surface finish of Ra 0.3–0.6 µm (12–24 µin) depending on the material, feed rate, and tool condition. Under optimal conditions — fine-grain carbide inserts, low feed rates, and stable cutting conditions — skiving can achieve Ra 0.2–0.4 µm. The surface character produced by skiving is directional, with visible feed marks corresponding to the feed rate. When skiving is combined with roller burnishing in a single-pass combination tool, the final surface finish improves to Ra 0.05–0.2 µm (2–8 µin) — equivalent to or better than honing. The surface produced by skiving and burnishing also has a favorable bearing ratio (Rmr) for hydraulic cylinder applications, typically with the characteristic plateau-valley surface structure that provides excellent sealing surface properties.
What causes chatter in skiving and how is it prevented?
Chatter in skiving is caused by vibration between the tool and workpiece, typically at frequencies of 100–1000 Hz. Common causes include insufficient tool rigidity (tool overhang too long — should be minimized), incorrect cutting speed (speed near the natural frequency of the tool-workpiece system — change speed by 20–30% to escape chatter), worn or improperly sharpened inserts (dull edges increase cutting forces that excite vibration), inadequate guide pad contact (pads not making consistent contact with the bore surface), and machine tool vibration (spindle bearing wear or loose machine elements). Chatter prevention includes: maintaining tool overhang at the minimum required for the bore length, selecting the correct insert grade and edge preparation for the material, ensuring all guide pads are adjusted to the correct diameter and making consistent contact, verifying machine rigidity before skiving operations, and using variable feed rates to disrupt chatter patterns in deep bores where tool length cannot be reduced.
Disclaimer: The skiving tool geometry parameters and cutting recommendations provided in this article are general guidelines based on industry-standard practices. Actual skiving tool design varies by manufacturer and specific application requirements. Tool geometry should be optimized through application testing under actual production conditions. Always consult the tool manufacturer's recommendations for specific skiving tool designs. The authors and publisher assume no liability for any damages or losses arising from the use of this information — always follow original equipment manufacturer guidelines for your specific equipment. Content is for informational purposes only and does not constitute professional engineering advice. Verify all parameters with qualified personnel before implementation as of 2026.