A 5% cobalt high-speed steel (AISI M35) that keeps its hardness hot. With about 6% tungsten, 5% molybdenum and 2% vanadium plus cobalt, M35 cuts at higher speeds than non-cobalt grades and holds an edge in tough materials.
What Is M35 High-Speed Steel?
M35 is a tungsten-molybdenum high-speed steel with 5% cobalt. The cobalt does not add hardness at room temperature but lets the steel keep its hardness at the high temperatures generated in fast cutting, so tool life extends dramatically on hard or abrasive work.
It is used for drills, end mills, broaches and reamers, especially where M2 would soften. It is brittle compared with tool steels and must be handled with rigid set-ups and correct speeds and feeds.
Supply Forms and Sizes
Every form is available soft-annealed (for further forming and machining) or heat-treated to your hardness window.
| Form | Condition | Size Range | Typical Use |
|---|---|---|---|
| Round bar / rod | Annealed | 3 – 100 mm | Tool blanks, drills |
| Flat bar | Annealed | 5 – 60 mm | Milling cutters, blades |
| Ground rod | Pre-ground | 3 – 40 mm | Precision tool stock |
| Saw & blade stock | Annealed | 2 – 20 mm | HSS saw blanks |
Chemical Composition (AISI M35)
| C | W | Mo | Cr | V | Co | P max | S max |
|---|---|---|---|---|---|---|---|
| 0.82 – 0.92 | 5.50 – 6.75 | 4.50 – 5.50 | 3.75 – 4.50 | 1.75 – 2.25 | 4.50 – 5.50 | 0.030 | 0.030 |
Heat analysis is reported on the mill certificate for every lot. If your drawing calls for tighter limits than the standard, flag it at enquiry — ladle-refined heats usually meet it without a surcharge.
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Elastic modulus (E) | ~200 GPa |
| Shear modulus (G) | ~79 GPa |
| Thermal conductivity | ~40 W/m·K at room temperature |
| Coefficient of thermal expansion | ~12 ×10⁻₆ /K (20 – 200 °C) |
Mechanical Properties
Typical as-hardened and tempered values. HSS hardness is measured on the Rockwell C scale; the mill certificate is the binding document.
| Condition | Hardness | Red-hardness* | Transverse strength | Notes |
|---|---|---|---|---|
| Annealed | ≤ 262 HB | — | — | For machining |
| H&T 64 HRC | 63 – 66 HRC | ~600 °C | ~3500 MPa | General Co-HSS |
| Triple tempered | 64 – 66 HRC | ~600 °C | ~3600 MPa | Max stability |
Equivalent Grades
| Standard | Designation |
|---|---|
| USA AISI | M35 |
| Europe EN | HS6-5-2-5 (similar) |
| Japan JIS G4403 | SKH55 (similar) |
| China GB/T 9943 | W6Mo5Cr4V2Co5 (similar) |
Heat Treatment and Processing
Preheat slowly, then raise to the grade forging range. Work above the lower limit and cool slowly after forging to avoid cracks.
800 – 860 °C, slow furnace cool to ~600 °C then air. Delivers soft condition for machining.
1180 – 1220 °C, oil or salt, then at least triple temper.
Around 540 – 560 °C, three tempers, to reach 64 – 66 HRC with stable austenite.
After machining or forming, 200 – 350 °C for 1 – 2 hours, air cool, to stabilise dimensions and relieve residual stress.
Heat-treated bars and plates are supplied with the hardness and test certificate you specify. For critical parts we can control decarburisation depth and supply a spheroidized or soft-annealed structure on request.
Applications of M35 High-Speed Steel
Hole making in alloy and stainless steels.
Milling where heat builds at the cutting edge.
Tough, wear-resistant finishing tools.
Complex profile tools needing edge retention.
Cutting hard or abrasive bar and tube.
Where tool life directly drives cost.
M35 High-Speed Steel vs Alternative Grades
| Grade | vs M35 High-Speed Steel | Choose It When |
|---|---|---|
| M35 | — | General cobalt HSS; good all-round hot hardness. |
| M2 (no Co) | Cheaper, lower red-hardness | Routine cutting where heat is moderate |
| M42 | Higher Co (8%), higher hardness | Toughest, hardest cutting jobs |
| T15 | Highest vanadium, max wear | Very abrasive work, lower toughness |
Quality Control and Mill Certificates
Every shipment ships with an EN 10204 3.1 mill certificate covering heat chemical analysis, hardness and the mechanical test on record. On request we add: ultrasonic test on heavy bar and plate, magnetic particle inspection on machined surfaces, and third-party inspection (SGS / BV) before loading. Dimensional tolerances follow the relevant EN / ASTM / JIS standard or your drawing.
Frequently Asked Questions
What is M35 high-speed steel?
A 5% cobalt tungsten-molybdenum HSS that holds its hardness at cutting temperatures, used for drills, end mills and broaches on hard materials.
M35 vs M2?
M35 adds cobalt for higher red-hardness and tool life in fast or hard cutting; M2 is cheaper and fine for routine work.
What hardness does M35 reach?
Typically 63 – 66 HRC after hardening and triple tempering.
Is M35 weldable?
It is brittle and hardenable; welding is generally avoided or done only by a qualified procedure.
What is the minimum order quantity?
Mill lots typically start at 200 kg per item; common sizes are often from stock.
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