Stainless steel is one of the most challenging materials to machine because of its high work-hardening rate, low thermal conductivity, and tendency to form built-up edge. Picking the wrong carbide insert grade can cut tool life by 70% or more. This guide shows you how to match insert grade to your specific stainless workpiece.
Understand the ISO M Classification
ISO 513 classifies stainless steel cutting under group M (yellow color code). Within this group, grades are numbered M01–M40, where lower numbers indicate higher wear resistance (finishing) and higher numbers indicate higher toughness (roughing/interrupted cuts).
Match Grade to Stainless Type
- 304/316 austenitic stainless — Use M15–M25 grades with PVD TiAlN or AlTiN coating. Recommended: Sandvik GC2220, Iscar IC907, Kennametal KCM25.
- 17-4 PH precipitation hardening — Need higher toughness, M25–M35. Walter WSM30S or Tungaloy AH725 perform well here.
- Duplex 2205, super duplex 2507 — Extreme work-hardening, use M30–M40 with reinforced edge prep. Sandvik GC2025 or Iscar IC830.
Coating Selection Matters
For stainless, PVD coatings outperform CVD because PVD leaves a sharper cutting edge and lower friction. The smooth coating surface reduces built-up edge formation. AlTiN coating handles temperatures up to 900°C, ideal for high-speed stainless machining.
Critical Cutting Parameters
Stainless steel rewards aggressive feed rates and conservative speeds. Typical starting parameters for a CNMG insert in 304 stainless:
- Cutting speed (Vc): 120–180 m/min
- Feed (fn): 0.20–0.35 mm/rev
- Depth of cut (ap): 1.5–3.0 mm
Avoid These Common Mistakes
Reducing feed below 0.15 mm/rev causes the insert to rub instead of cut, accelerating work hardening and dramatically shortening tool life. Always maintain a feed rate above the cutting edge radius. Also avoid running stainless at cast iron speeds — it generates excessive heat and edge chipping.
Where to Buy
Hooguu stocks original carbide inserts from Sandvik Coromant, Iscar, Kennametal, Walter, and Kyocera. Browse our full carbide insert catalog.
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