Understanding Steel Grades for CNC-Turned Parts

When manufacturing special fasteners and precision-turned components, choosing the correct steel grade is just as important as the accuracy of the CNC machine itself. Each grade offers different strengths, machinability, corrosion resistance, and suitability for heat treatment — all of which impact the performance and reliability of the finished product.

At Pattern Fasteners, we manufacture steel turned parts from 0.5mm to 250mm diameter, using both manual and CNC lathes, and provide BS EN 10204 3.1 mill certificates to verify material chemistry and mechanical properties. Below, we explore the most commonly used steel grades for CNC turning.

Common Steel Grades Used in CNC Turning

 

1. EN1A (230M07) – Free-Cutting Mild Steel

Best for: High-volume production, intricate turned parts, threaded components.
Why it’s used:

• Excellent machinability

• Ideal for CNC lathes working at high speeds

• Produces fine finishes

• Suitable for small precision fasteners

Typical Pattern Fasteners applications:

• Spacers

• Turned washers

• Custom screws

• General precision turned components requiring efficiency and accuracy

 

2. EN3B (070M20) – General Purpose Mild Steel

Best for: Structural components, medium-strength fasteners
Why it’s used:

• Better mechanical strength than EN1A

• Suitable for case hardening

• Good for components needing added surface durability

Typical applications:

• Studs

• Pins

• Shafts

• Fasteners requiring a tough core with a hardened exterior

 

3. EN8 (080A40) – Medium Carbon Steel

Best for: High-strength precision components
Why it’s used:

• Stronger and more wear-resistant than mild steels

• Suitable for flame or induction hardening

• Excellent for load-bearing fasteners

Typical applications:

• Axles

• Couplings

• Shear pins

• High-strength custom fasteners

 

4. EN16 / EN16T (605M36) – High Tensile Steel

Best for: Tough, shock-resistant components
Why it’s used:

• High tensile strength

• Good ductility

• Heat-treatable

• Ideal for dynamic environments

Typical applications:

• Automotive/industrial fasteners

• Couplings

• High-stress precision parts

• Components exposed to vibration or impact

 

5. EN19 / EN19T (4140 / 709M40) – Chrome-Moly Steel

Best for: Heavy-duty engineered fasteners & precision machined parts
Why it’s used:

• Extremely strong

• High fatigue resistance

• Hard-wearing and heat-treatable to high hardness levels

Typical applications:

• Bolts for mechanical assemblies

• Drive components

• Torque-bearing parts

• High-strength studs

 

 

6. EN24 / EN24T (817M40) – Nickel-Chrome-Moly Alloy Steel

Best for: High-performance turning work requiring toughness + hardness
Why it’s used:

• Exceptional strength even in large diameters

• Good wear resistance

• Suitable for demanding precision components

Typical applications:

• Aerospace-grade fasteners

• Heavy-duty shafts

• Gears & drive components

• High-performance custom bolts

 

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Why Steel Grade + Finish Selection Matters for Special Fasteners

For bespoke fasteners and precision components, the correct combination determines:

• Performance under load

• Wear life

• Resistance to corrosion

• Dimensional stability

• Cost efficiency

• Suitability for harsh environments

At Pattern Fasteners, the selection is always based on real-world application requirements:

- Mechanical strength
- Material certificates (BS EN 10204 3.1)
- Environmental exposure
- Machinability
- Delivery times & repeatability

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