Selecting the correct high speed steel can improve tool life, cutting efficiency, dimensional accuracy and machined surface quality.

The hardest or most expensive steel is not automatically the best choice. A cutting tool must balance wear resistance, red hardness and toughness according to its geometry, workpiece material and operating conditions.

M2, M42 and T1 each provide a different balance of properties.

Important Properties of High Speed Steel

Hardness

Hardness allows the cutting edge to resist abrasive wear and plastic deformation. Many HSS grades achieve hardness above 63 HRC after suitable heat treatment.

A higher hardness may improve edge life but can also reduce toughness and increase the risk of chipping.

Red Hardness

Red hardness is the ability of HSS to retain hardness as cutting temperature rises.

It is particularly important for:

• High-speed machining
• Dry cutting
• Limited-coolant operations
• Continuous heavy cutting
• Heat-resistant workpieces

M42 generally provides the strongest red hardness among M2, M42 and T1. T1 also offers reliable high-temperature performance, while M2 meets most general cutting requirements.

Wear Resistance

Wear resistance determines how long a cutting edge retains its geometry. Tungsten, molybdenum and vanadium contribute to the formation of hard wear-resistant carbides.

The required wear resistance increases with:

• Workpiece hardness
• Cutting speed
• Production volume
• Abrasive inclusions
• Cutting temperature

Toughness

Toughness helps prevent chipping and complete fracture.

It is especially important for:

• Taps
• Thin drills
• Small tools
• Milling cutters
• Broaches
• Interrupted cutting
• Unstable machining conditions

M2 generally offers a favourable balance of toughness and wear resistance.

Select HSS by Workpiece Material

Carbon and Low-Alloy Steel

M2 is normally a suitable starting grade for carbon steel and low-alloy steel. It provides reliable hardness, toughness and wear resistance without the cost of cobalt HSS.

Stainless Steel

Stainless steel generates considerable heat and has a strong work-hardening tendency. M42 may provide better edge retention and red hardness, especially during high-volume machining.

High-Strength and Hardened Steel

Harder workpieces place greater pressure on the cutting edge. M42 may be selected when high hardness and resistance to softening are required.

Titanium and Nickel-Based Alloys

Titanium and nickel-based alloys generate high local temperatures and can cause rapid tool wear. M42 is generally more suitable because its cobalt content improves red hardness.

Aluminium and Non-Ferrous Metals

M2 is usually sufficient for aluminium, copper and similar non-ferrous metals. Tool geometry, chip evacuation and surface finish may be more important than using a higher-alloy grade.

Select HSS by Cutting Tool

Drill Bits

M2 is widely used for general-purpose drills because it combines toughness, wear resistance and grindability.

M42 may be selected for drilling stainless steel, hardened materials and heat-resistant alloys.

Taps

Taps experience high torsional loading and can fail suddenly.

M2 is suitable for general threading applications. M42 may provide better wear resistance for difficult materials, although the increased hardness must be balanced against fracture risk.

Milling Cutters

Milling involves interrupted cutting forces. M2 provides useful toughness for general milling, while M42 can improve edge retention when machining demanding materials.

Reamers

Reamers require dimensional stability and wear resistance. M2 is suitable for general reaming. M42 may be preferred for longer production runs or difficult workpieces.

Broaches and Gear Cutters

Broaches and gear-cutting tools are complex and costly. Grade selection should balance edge wear, toughness, dimensional stability and regrinding requirements.

Grade Selection Guide

This table provides an initial recommendation. Cutting tests may be required to determine the most economical grade.

Identify the Tool-Failure Mode

Rapid Wear

When a cutting edge gradually becomes dull, consider:

• A harder HSS grade
• M42 instead of M2
• Better tool coating
• Lower cutting speed
• Improved cooling

Edge Chipping

When small pieces break from the edge, consider:

• A tougher grade
• M2 instead of harder cobalt HSS
• Lower working hardness
• Improved edge geometry
• Reduced vibration

Complete Fracture

Complete tool failure can result from:

• Insufficient toughness
• Excessive torsional load
• Grinding cracks
• Poor heat treatment
• Sharp stress concentration
• Poor chip evacuation

Changing the steel grade alone will not correct an unsuitable tool design or machining process.

Plastic Deformation

When the cutting edge bends or loses its geometry, consider:

• Higher working hardness
• Better red hardness
• Improved heat treatment
• Reduced cutting temperature
• M42 for demanding conditions

Consider Total Tool Cost

The purchase price of HSS is only part of the total cost. Buyers should also consider:

• Machining cost
• Grinding cost
• Heat treatment
• Coating
• Tool life
• Regrinding frequency
• Tool-change downtime
• Cost per finished part

M42 may have a higher initial cost, but it can be economical when longer tool life reduces downtime. M2 may provide a lower total cost for general machining where cobalt HSS is unnecessary.

Final Selection

Choose M2

Choose M2 for general-purpose drills, taps, milling cutters, reamers and saw blades requiring balanced hardness, toughness, wear resistance and cost.

Choose M42

Choose M42 for stainless steel, titanium, nickel alloys and high-temperature cutting applications requiring exceptional red hardness and edge retention.

Choose T1

Choose T1 when a tungsten-based HSS grade is specified or when stable wear resistance and high-temperature performance are required.

M2 is the preferred starting grade for general-purpose cutting tools. M42 is suitable for difficult materials and high cutting temperatures, while T1 provides traditional tungsten-based HSS performance.

Huangshi Xiri supplies M2, M42 and T1 high speed tool steel in round bars, flat bars and custom-cut sizes. Send us your required grade, dimensions, quantity and application for technical support and a quotation.

FAQs

What is the best high speed steel for drill bits?

M2 is widely used for general drills. M42 may be better for stainless steel and difficult-to-machine alloys.

Which HSS grade is suitable for taps?

M2 provides a good toughness-to-wear balance for general taps. M42 can improve wear resistance in demanding applications.

Which is the hardest grade among M2, M42 and T1?

M42 generally achieves the highest working hardness after suitable heat treatment.

Is harder HSS always better?

No. Excessive hardness may reduce toughness and increase the risk of chipping or fracture.