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Material Reference

Steel Grades for CNC Machining

Compare 12 steel grades side by side. See strength, hardness, machinability, and best uses. Find the right steel for your next project.

Grade ▲▼ Type ▲▼ Tensile (ksi) ▲▼ Yield (ksi) ▲▼ Hardness ▲▼ Machinability ▲▼ Weldability ▲▼ Corrosion Res. ▲▼ Common Uses
1018 Carbon 63 53 126 HB Excellent Excellent Poor General purpose, shafts, pins
1045 Carbon 91 77 179 HB Good Good Poor Gears, axles, bolts
12L14 Carbon 78 60 163 HB Excellent Poor Poor Screw machine parts, fittings
4130 Alloy 97 63 197 HB Good Good Fair Aircraft, motorsport, tubing
4140 Alloy 95 60 197 HB Good Fair Fair Shafts, gears, tooling
4340 Alloy 108 68 217 HB Fair Fair Fair Landing gear, crankshafts
8620 Alloy 90 60 180 HB Good Good Poor Gears, camshafts, pins
A2 Tool Steel Tool 230 - 57-62 HRC Poor Poor Fair Dies, punches, tooling
D2 Tool Steel Tool 248 - 58-64 HRC Poor Poor Good Cutting tools, dies, wear parts
O1 Tool Steel Tool 200 - 57-62 HRC Fair Poor Poor Gauges, jigs, knife blades
S7 Tool Steel Tool 210 - 54-58 HRC Fair Poor Fair Impact tools, chisels
M2 HSS HSS 230 - 60-65 HRC Poor Poor Fair Drill bits, end mills, taps

Grade Details

1018 Carbon
  • Tensile Strength63 ksi
  • Yield Strength53 ksi
  • Hardness126 HB
Machinability: Excellent Weldability: Excellent Corrosion: Poor
Uses: General purpose, shafts, pins
Best for: Low-cost parts that need welding
1045 Carbon
  • Tensile Strength91 ksi
  • Yield Strength77 ksi
  • Hardness179 HB
Machinability: Good Weldability: Good Corrosion: Poor
Uses: Gears, axles, bolts
Best for: Stronger parts that still need welding
12L14 Carbon
  • Tensile Strength78 ksi
  • Yield Strength60 ksi
  • Hardness163 HB
Machinability: Excellent Weldability: Poor Corrosion: Poor
Uses: Screw machine parts, fittings
Best for: High-speed screw machine work
4130 Alloy
  • Tensile Strength97 ksi
  • Yield Strength63 ksi
  • Hardness197 HB
Machinability: Good Weldability: Good Corrosion: Fair
Uses: Aircraft, motorsport, tubing
Best for: Aircraft tubing and race car frames
4140 Alloy
  • Tensile Strength95 ksi
  • Yield Strength60 ksi
  • Hardness197 HB
Machinability: Good Weldability: Fair Corrosion: Fair
Uses: Shafts, gears, tooling
Best for: The go-to steel for most CNC machined parts
4340 Alloy
  • Tensile Strength108 ksi
  • Yield Strength68 ksi
  • Hardness217 HB
Machinability: Fair Weldability: Fair Corrosion: Fair
Uses: Landing gear, crankshafts
Best for: High-stress parts that need toughness
8620 Alloy
  • Tensile Strength90 ksi
  • Yield Strength60 ksi
  • Hardness180 HB
Machinability: Good Weldability: Good Corrosion: Poor
Uses: Gears, camshafts, pins
Best for: Case-hardened gears and wear surfaces
A2 Tool Steel Tool
  • Tensile Strength230 ksi (hardened)
  • Yield Strength-
  • Hardness57-62 HRC
Machinability: Poor Weldability: Poor Corrosion: Fair
Uses: Dies, punches, tooling
Best for: Stamping dies and blanking punches
D2 Tool Steel Tool
  • Tensile Strength248 ksi (hardened)
  • Yield Strength-
  • Hardness58-64 HRC
Machinability: Poor Weldability: Poor Corrosion: Good
Uses: Cutting tools, dies, wear parts
Best for: Parts that must resist wear and abrasion
O1 Tool Steel Tool
  • Tensile Strength200 ksi (hardened)
  • Yield Strength-
  • Hardness57-62 HRC
Machinability: Fair Weldability: Poor Corrosion: Poor
Uses: Gauges, jigs, knife blades
Best for: Gauges, jigs, and precision cutting edges
S7 Tool Steel Tool
  • Tensile Strength210 ksi (hardened)
  • Yield Strength-
  • Hardness54-58 HRC
Machinability: Fair Weldability: Poor Corrosion: Fair
Uses: Impact tools, chisels
Best for: Tools that take heavy impact loads
M2 HSS HSS
  • Tensile Strength230 ksi (hardened)
  • Yield Strength-
  • Hardness60-65 HRC
Machinability: Poor Weldability: Poor Corrosion: Fair
Uses: Drill bits, end mills, taps
Best for: Cutting tools that stay sharp at high temps

How to Pick the Right Steel Grade

Steel comes in many grades. Each one trades off strength, hardness, machinability, and cost. The right pick depends on your part's job.

Carbon Steels

Carbon steels (1018, 1045, 12L14) are cheap and easy to get. 1018 welds well and machines fast. 1045 is stronger and works for gears and bolts. 12L14 is the fastest to machine. Use it for high-volume screw machine parts.

Alloy Steels

Alloy steels (4130, 4140, 4340, 8620) add chromium, molybdenum, or nickel. These elements boost strength and wear resistance. 4140 is the most popular. Think of it as the "6061 of steels." It handles most jobs well.

4340 is stronger and tougher. Use it for landing gear, crankshafts, and other high-stress parts. 8620 is the go-to for case hardening. Its soft core absorbs shock while the hard surface resists wear.

Tool Steels

Tool steels (A2, D2, O1, S7, M2) are made for hardness. They hold an edge and resist wear. But they are hard to machine. Most shops cut them in the soft state, then heat treat.

D2 has the best wear resistance. S7 handles impact best. M2 stays hard at high cutting temperatures.

Pro Tip

4140 pre-hard is the best all-around steel for CNC machining. It arrives heat treated to 28-34 HRC. You skip the heat treatment step and save time and money.

Quick Decision Guide

  • Need to weld? → 1018 or 4130
  • Need strength? → 4340
  • Need machinability? → 12L14
  • Need wear resistance? → D2 Tool Steel
  • Good all-around? → 4140 pre-hard

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Frequently Asked Questions

4140 pre-hardened steel is the most popular. It has good strength, machines well, and comes ready to use. You do not need extra heat treatment. 12L14 is also common when fast machining speed matters most.
4340 is stronger than 4140. It has 108 ksi tensile strength versus 95 ksi. 4340 also has more nickel, which makes it tougher. Use 4340 for high-stress parts like landing gear. Use 4140 for general shafts and gears where extreme strength is not needed.
Yes, but it is difficult. Steel above 45 HRC needs carbide or CBN tooling. Speeds must be slow. Tool wear is high. Most shops machine steel soft, then heat treat it. If you must machine hardened steel, expect higher costs and longer lead times.
Case hardening makes the outside of a part hard. The inside stays soft and tough. The part is heated in a carbon-rich environment. Carbon soaks into the surface. Then the part is quenched. 8620 is the most common grade for this process. It is used for gears, camshafts, and pins.
Pre-hard means the steel was heat treated before you buy it. It arrives at a known hardness, usually 28-34 HRC. You machine it as-is. No heat treatment after machining. 4140 pre-hard is the most common example. It saves time and cost.

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