ISO P — Steel · P10
P10 — Alloy steel
Hardness range: 180–280 HB. Part of the ISO P — Steels group. Steel is the most widely machined material. Carbon and alloy steels are the target material for the majority of turning and milling operations. Hardness ranges from ~125 HB (low-carbon) to 350 HB (high-strength structural). CVD-coated carbide (TiCN/Al₂O₃ multilayer) dominates. Positive geometry for finishing, negative for heavy roughing.
Material profile — P10
- ISO designation
- P10 (ISO P — Steels)
- Material
- Alloy steel
- Hardness
- 180–280 HB
- ISO group colour
- Steel
Tooling guidance — P-group
- Group summary
- CVD-coated carbide at Vc 200–400 m/min. Positive geometry for finishing, negative for roughing.
Insert selection for 4140 / 4340 alloy steel (annealed) — starting point
- ISO application class
- P (steel). Match the insert's ISO class, not the brand name. Sandvik, Kennametal, Iscar, Walter, Seco and Mitsubishi each publish a P-class grade — pick by ISO class, then confirm the exact grade for your condition.
- Grade & coating
- CVD-coated carbide, P15–P25 general; tougher P25–P35 for roughing, P10–P20 for finishing. Annealed alloy steel (4140 / 4340, ~180–280 HB) takes higher speeds than its heat-treated form.
- Geometry
- Negative geometry is economical for roughing; positive for finishing and low-rigidity work. Use a medium chipbreaker so soft alloy steel does not run long, stringy chips.
- Starting parameters
- Vc ≈ 200–300 m/min, fn ≈ 0.10–0.40 mm/rev. Typical starting band — confirm in the advisor or on a sample part.
Selection table: alloy steel (4140 / 4340, annealed)
| Operation | Geometry | ISO class | Coating family | Coolant | First check |
|---|---|---|---|---|---|
| Roughing | Negative geometry, economical; medium chipbreaker | P25–P35 | CVD-coated carbide | Per process | Chipbreaker: stringy chips mean feed too low or wrong breaker |
| Finishing | Positive geometry, medium chipbreaker | P10–P20 | CVD-coated carbide | Per process | Built-up edge at low speed: raise Vc, sharper edge |
| Interrupted cut | Negative geometry with a robust edge | P25–P35 | CVD-coated carbide | Per process | Crater wear at high speed: ease Vc |
| Low rigidity / thin wall | Positive geometry for low-rigidity work | P10–P20 | CVD-coated carbide | Per process | Flank wear: balance Vc and grade hardness |
4140 / 4340 alloy steel (annealed): what goes wrong, and what to check first
- Built-up edge at low speed
- Soft alloy steel welds to the edge below the working band. Raise Vc, use a sharper positive edge, and add coolant. See the tool-wear guide.
- Long stringy chips / bird-nesting
- Feed too low or the wrong chipbreaker. Increase fn or pick a roughing breaker so chips break instead of nesting.
- Crater wear at high speed
- Heat wears a crater behind the edge. Use a CVD grade and ease Vc.
- Flank wear
- Normal abrasion that sets tool life. Balance Vc and pick a harder grade for longer runs.
Reference data
Frequently asked questions
What insert grade should I use for 4140 / 4340 alloy steel?
A CVD-coated carbide in the ISO P class, P15–P25. Match the ISO P class across brands rather than the brand name and confirm the exact grade in the advisor.
What cutting speed for annealed alloy steel with carbide?
Roughly Vc 200–300 m/min and fn 0.10–0.40 mm/rev; annealed steel runs faster than its heat-treated form. Treat this as a starting band and confirm on a sample part.
Why do I get long stringy chips on 4140?
Feed too low or the wrong chipbreaker. Increase the feed or choose a roughing breaker so the chips break instead of bird-nesting.
Why is there built-up edge on soft alloy steel?
You are cutting below the working speed band. Raise the cutting speed, use a sharper positive edge, and add coolant.
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Grade designations in this group
Each page cross-references the EN, Werkstoffnummer, AISI/UNS and JIS designations for one material, with the ISO machining group it falls in.
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