How to Select Tool Steels

A practical route from application to grade. Relative property ratings for ten common tool steels, a selection table by application and working condition, and the technical checks to run before a grade is fixed. Use it as a starting point, then confirm with your heat treater and a service trial.

1Find the tool application
2Identify the working condition
3Check the required property
4Compare suitable grades
5Confirm process limits

1. Property ratings of common tool steels

Relative ratings for ten grades that cover most die, tool and mold work. Higher is better for every column, and all four columns share the same scale.

Grade	Type	Abrasion resistance	Toughness	Machinability	Grindability
High-speed tool steels
M4	High-speed, molybdenum	103	14	60	10
M2	High-speed, molybdenum	95	20	65	10
Cold-work tool steels
D2	Cold work, high-chromium	100	20	60	10
A2	Cold work, air-hardening	65	40	65	44
O1	Cold work, oil-hardening	50	14	90	72
A8	Cold work, air-hardening	48	75	60	75
O6	Cold work, oil-hardening	44	10	125	76
Hot-work tool steels
H13	Hot work, chromium	30	100	75	100
Shock-resisting tool steels
S5	Shock-resisting	44	90	65	85
S7	Shock-resisting	42	103	75	92

^(a) Abrasion resistance. M4, D2, and M2 have the highest abrasion-resistance ratings in this comparison.
^(b) Toughness. S7, H13, and S5 have the highest toughness ratings in this comparison.
^(c) Machinability. O6 and O1 are easier to machine than high-wear-resistance grades such as D2, M2, and M4.
^(d) Grindability. H13, S7, and S5 are easier to grind, while D2, M2, and M4 are more difficult.
^(e) Reading the bars. All four properties are indexed on the same relative scale, so a longer bar means a higher rating for that property, not a higher overall ranking of the grade.

2. Tool steel selection by application

Starting point by tool and working condition. It does not replace application testing or heat-treatment confirmation. Grade names link to the grade pages.

Application / tool	Working condition	Main required property	General grade	Higher-performance grade
Cutting tools	Light cuts, slow speeds	Wear resistance with acceptable grindability	O1, A2	M2
Cutting tools	Heavy cuts, fast speeds	Wear resistance and hot hardness	M2	M4, T1, M42
Boring tools	Metal cutting	Hot hardness and wear resistance	M2	M4
Broaches	Metalworking	Wear resistance and hot hardness	M2	M4
Form cutters	Profile cutting	Wear resistance and hot hardness	M2	M4
Milling cutters	Continuous cutting	Hot hardness and edge wear resistance	M2	M4
Thread cutters	Thread cutting	Wear resistance and hot hardness	M2	M4
Woodworking cutters	Edge wear with regrinding requirement	Wear resistance and grindability	O1	M2
Cold shear blades	Light gauge stock	Wear resistance with moderate toughness	A2	D2
Cold shear blades	Heavy gauge stock	Impact resistance and cracking resistance	S5	S7
Hot shear blades	Hot cutting	Hot hardness and toughness	S7, A8	H13, H21
Paper knives	Edge wear	Wear resistance	D2	M2, M4
Rotary knives	Continuous cutting wear	Wear resistance	A8	D2
Chipper knives	Impact and edge wear	Toughness with wear resistance	A2, A8	D2, M2
Blanking dies	Cold work, short runs	Balanced wear resistance and machinability	O1, O6	A2
Blanking dies	Cold work, long runs	Wear resistance and dimensional stability	A2	D2, M2
Bending dies	Cold forming	Toughness and dimensional stability	O1, O6	A2, D2
Coining dies	High pressure cold work	Wear resistance and compressive strength	O1	A2, D2
Embossing dies	Cold pressure and surface detail	Wear resistance and dimensional stability	A2	D2
Cold forming dies	General forming	Wear resistance with stability	O1	A2, D2
Hot forming dies	Hot work	Hot hardness and toughness	H13, S7	H21
Cold extrusion dies	High pressure and wear	Wear resistance with enough toughness	D2	M2
Hot extrusion dies for aluminum	Heat softening and thermal fatigue	Hot hardness and toughness	H13	H11, H21
Hot extrusion dies for copper and brass	Higher hot wear and thermal load	Hot hardness and thermal resistance	H13	H21
Die casting dies	Thermal fatigue, heat checking, cracking	Hot work stability	H13	Premium H13 / ESR H13
Brass die casting dies	Higher hot wear	Hot hardness and heat resistance	H13	H21
Hot forging dies	Heat, impact, thermal fatigue	Toughness and hot hardness	H13, S7	H21, H43
Hot trimming dies	Hot impact and edge damage	Toughness and hot hardness	S7, H13	H21
Cold heading tools	Impact, pressure, wear	Toughness and wear resistance	A2, S7	D2, M2
Cold punches	Piercing, trimming, forming	Wear resistance and toughness	A2, S7	D2, M2
Heavy-duty punches	Shock-loaded punching	Toughness first	S5	S7
Draw punches	Drawing pressure and wear	Wear resistance and toughness	A2, D2	M2
Thread rolls	Surface pressure and wear	Wear resistance	D2	M2
Forming rolls	Rolling pressure and wear	Wear resistance and dimensional stability	O1, A2	D2, D7
Drive rolls	Wear under contact pressure	Wear resistance	D2	D7
Wire drawing tools	Sliding wear and surface pressure	Wear resistance	D2	M4
Plug gauges	Wear and dimensional stability	Wear resistance and stability	A2	D2
Master hobs	Accuracy and wear resistance	Wear resistance and stability	S7	A2, D2
Cutting hobs	Cutting wear and heat	Hot hardness and wear resistance	M2	T1
Lathe tools	Cutting heat and wear	Hot hardness	M2	M42
Planer tools	Cutting wear	Hot hardness and wear resistance	M2	M4
Shaper tools	Cutting wear	Hot hardness and wear resistance	M2	M4
Reamers	Cutting accuracy and wear	Wear resistance and hot hardness	M2	M4
Taps	Thread cutting wear	Wear resistance and hot hardness	O1	M2
Drills	Cutting heat and edge wear	Hot hardness and wear resistance	M2	M4
Drill bushings	Wear from repeated drilling	Wear resistance	S5	A2
Brake dies	Bending pressure	Toughness and wear resistance	4140 HT	A2
Gripper dies, cold	Holding pressure and wear	Wear resistance and toughness	O1, S7	A2, D2
Gripper dies, hot	Hot gripping and wear	Hot hardness and toughness	S7, H13	H21
Swaging dies, cold	Impact and forming pressure	Toughness and wear resistance	S7	D2
Swaging dies, hot	Heat and impact	Hot hardness and toughness	H13, S7	H21
Lamination dies	Wear and edge stability	Wear resistance	A2	D2, M2
Plastic molds	Machining, polishing, mold surface quality	Machinability and polishability	P20, H13	420, special mold steels
Impact tools	Repeated shock	Toughness	S5	S7
Battering tools, cold	Shock and breakage	Toughness	S5	S7
Blacksmith tools	Impact and heat	Toughness	S5	S7
Boiler-shop tools	Impact work	Toughness	S5	S7
Chisels, cold working	Impact and edge chipping	Toughness	S5	S7
Chisels, hot working	Heat and impact	Toughness and hot hardness	S7	M2
Pneumatic tools	Repeated impact	Toughness	S5	S7
Concrete breakers	Severe impact	Toughness	S5	S7
Screwdriver bits	Torsion and impact	Toughness	S5	S7
Arbors	Support and wear	Toughness and dimensional stability	O1, O6	A2, D2
Collets	Holding pressure and wear	Toughness and wear resistance	O1	S5, S7
Chuck jaws	Holding pressure and impact	Toughness	S5	S7

3. Selection notes

How to read the failure mode before changing a grade.

Selection note	Meaning
If the tool wears gradually, start by comparing wear-resistant grades.	D2, M2, M4, and related grades are common starting points for abrasive wear.
If the tool chips, cracks, or breaks suddenly, check toughness before increasing hardness.	S7, S5, H13, and other tougher grades may be more suitable for shock-loaded tools.
If the tool works under heat, room-temperature hardness is not enough.	Hot hardness and resistance to softening become more important.
If the tool requires frequent sharpening, grindability affects maintenance cost.	High-wear-resistance grades may be harder to grind.
If the tool is large or complex, heat-treatment distortion must be considered.	Air-hardening grades are often used where dimensional stability is important.
If the production run is short, the highest-performance grade may not be economical.	Machinability and material cost may be more important for short-run tooling.
If the production run is long, higher wear resistance may reduce total cost.	More expensive grades can be justified when they reduce downtime and replacement frequency.

4. Final technical check before grade selection

Confirm these nine points with the tool shop and heat treater before the grade is fixed.

Check item	Confirm before selection
Tool function	Cutting, shearing, forming, drawing, extrusion, rolling, impact, molding
Working temperature	Room temperature, warm work, hot work
Main failure mode	Wear, chipping, cracking, softening, deformation, distortion
Load level	Light, medium, heavy, shock-loaded
Production volume	Short run, medium run, long run
Section size	Small tool, thick section, large die block
Heat treatment target	Required hardness, toughness, distortion control
Finishing requirement	Machining, grinding, polishing, sharpening
Cost target	Material cost, machining cost, maintenance cost, cost per part

Related reference pages

General properties of tool steels · Tool steel composition chart · Grade comparison and equivalents · Hot hardness chart · Hardening and tempering temperatures · Machinability ratings

Grade families: cold-work tool steels · hot-work tool steels · high-speed steels · plastic mold steels · tool steel material finder · tool steel catalog

Property ratings are relative comparison values for selection, not mechanical test results. Application notes are a starting reference only: final performance depends on steel quality, heat treatment, section size, tool design and service conditions. Verify the grade and the heat-treatment procedure before production.