Not all steel is the same — and not all applications are the same. This guide maps the engineering steel grades we stock to the industries and components they are actually used in, with the reasoning behind each recommendation.
The broadest sector — covering sub-contract machining, jig and fixture manufacture, general fabrication and light to medium machinery. Grade selection here is driven by machinability, cost-effectiveness and the mechanical properties needed for the specific component.
EN8 (080M40) is the workhorse for general shafts and spindles — stronger than mild steel and machinable in both normalised and hardened & tempered condition. For higher-stressed shafts, or where the section size exceeds EN8's hardenability, EN19 (708M40 / 42CrMo4) provides significantly higher tensile strength and better deep-section hardening. EN3B suits light-duty shafts where strength requirements are modest.
EN8M (212A42) is the preferred grade for high-volume fastener production on automatic lathes — the elevated sulphur gives excellent chip-breaking at higher cutting speeds whilst retaining EN8-level strength. For high-tensile studs (Grade 8.8 and above), EN19 in the T condition provides the necessary tensile strength with good machinability.
Jigs and fixtures require dimensional stability, good machinability and moderate strength — but not usually the premium properties of alloy grades. EN8 normalised is widely used for its combination of rigidity, machinability and cost-effectiveness. EN3B suits lighter tooling and brackets. S355 is preferred where welded fabrication is involved.
Woodruff keys, parallel keys and dowel pins are typically machined from EN8 or EN3B bright drawn hexagon or square bar — the bright drawn condition provides a clean, accurate starting size that minimises material removal. EN1A is specified where the component is complex or produced in quantity on an automatic lathe and strength requirements are modest.
Light-duty gears and sprockets require a hard, wear-resistant tooth flank with a tough core to resist shock loading — a combination achieved by case hardening. 8620 (805M20) is the most cost-effective choice for moderate-duty applications. EN36 (655M13) provides superior core toughness for more demanding loading. Both are carburised and hardened to 58–64 HRC on the tooth surface.
Automotive applications demand high strength-to-weight, fatigue resistance and consistent heat treatment response. Sub-contract machinists serving OEM and Tier 1 suppliers encounter demanding specifications — often with recognised international grade equivalents.
EN19 (42CrMo4 / AISI 4140) is the global standard for automotive transmission shafts — its Cr-Mo chemistry is recognised worldwide and it delivers the high tensile strength and fatigue resistance that drivetrain components demand. For heavily stressed or large-section shafts, EN24T (34CrNiMo6 / AISI 4340) adds nickel for superior deep-section hardenability and impact toughness.
SAE 8620 (805M20) is the most widely used case hardening steel in the global automotive supply chain, specified by name in countless gearbox and differential gear drawings. It provides a reliable combination of case hardness (58–62 HRC) and core toughness. For performance and motorsport applications, EN36 (655M13) delivers superior core impact resistance where shock loading is severe.
Camshafts require a wear-resistant lobe surface to withstand repeated contact with tappets, combined with adequate core toughness for the bending loads imposed by the valve train. SAE 8620 satisfies both requirements after carburising — consistent with OEM specifications used in passenger car and light commercial engine production worldwide.
EN1A (230M07 / 11SMn30) is used extensively for wheel nuts, inserts and small hydraulic fittings produced on automatic lathes — its free-cutting properties dramatically reduce cycle times on high-volume CNC turning. EN8 is specified where greater strength is needed, such as stub axle components and brake caliper parts subject to significant stress.
Downhole, wellhead and surface processing equipment operates under extreme pressure, corrosive environments and demanding cyclic loading. Grade selection is driven by strength, toughness, sour service resistance and traceability requirements.
EN24T (817M40T / 34CrNiMo6 / AISI 4340) is the primary grade for downhole drill collars and tool joints. Its combination of high tensile strength (900–1150 N/mm² in the T condition), excellent toughness and consistent properties in large cross-sections makes it the standard choice for components that must withstand the combined bending, torsion and tension loads of a drill string.
EN19 (42CrMo4) is widely used for wellhead valve bodies, actuator shafts and choke components machined from large-diameter round bar. Its high tensile strength, good machinability in the normalised condition and recognised international designation (42CrMo4 / 4140) satisfy most operator material specifications. 3.1 material test certificates are standard.
Pressure vessel and flange studs for oil and gas service require high tensile strength (typically 860–1000 N/mm²) and guaranteed low-temperature Charpy impact values. EN19 in the T condition satisfies the majority of ASME and API bolting specifications. EN40B (722M24) is specified when a nitrided surface is required to resist galling in high-torque stud applications.
Centrifugal and reciprocating pump shafts for oil field service must withstand fatigue loading, potential corrosion and moderate impact. EN19 (42CrMo4) in the T condition covers the majority of applications. Where pumps handle abrasive media or where shaft stiffness in large diameters is critical, EN24T provides higher strength and better large-section properties.
Agricultural machinery is subjected to impact loading, abrasive wear from soil and crop material, and exposure to moisture. Grade selection prioritises toughness, wear resistance and cost-effectiveness — often in large section sizes for heavy equipment.
Power take-off shafts and agricultural driveline components are subject to high torque and impact loads, particularly when encountering ground obstructions. EN8 (080M40) in the normalised or hardened & tempered condition satisfies the majority of agricultural driveline specifications at acceptable cost. Heavily stressed shafts for larger tractors and combine harvesters often step up to EN19.
EN9 (070M55) is the preferred grade for soil-engaging tools — its higher carbon content (nominally 0.55% C) gives significantly better wear resistance and hardness after heat treatment than EN8, making it suitable for cultivator tines, reversible plough shares and spring tines. The higher hardness means EN9 resists the abrasive wear from soil particles that would rapidly degrade a lower-carbon grade.
Hitch pins, pivot bolts and three-point linkage components must withstand repeated shock loading from rough terrain. EN8 covers most standard agricultural linkage applications. For heavily loaded pivot pins on large cultivation equipment, EN36 case hardened provides a wear-resistant surface and shock-resistant core that significantly extends service life in abrasive conditions.
Grey cast iron bar is used for bushings, bearing housings and wear-resistant slideways where its self-lubricating graphite structure and damping properties are particularly beneficial.
Hydraulic and pneumatic components require precise dimensional tolerances, excellent surface finish and resistance to wear and fatigue under cyclic pressure loading. Nitrided and case hardened grades are common where seal integrity and bore surface quality are critical.
EN40B (722M24 / 31CrMo12) is the premier grade for nitrided hydraulic cylinder rods. Supplied in the Q+T condition then precision-ground and gas nitrided to 700–850 HV surface hardness, it provides exceptional wear resistance at the seal contact zone, minimal dimensional change during nitriding, and excellent fatigue strength under cyclic loading. The hard chrome alternative is declining for environmental reasons — nitrided EN40B bar is increasingly the specified replacement.
Hydraulic valve spools and fittings are produced in large quantities on CNC lathes and automatic screw machines — making machinability the primary grade criterion. EN1A (230M07 / 11SMn30) is ideal for smaller fittings, adaptors and connectors where the pressure rating allows it. For higher-pressure components and valve bodies that require greater strength, EN8 is specified instead.
Hydraulic pump pistons and plungers are subject to high contact stress, wear at the bore interface and cyclic fatigue loading. EN19 (42CrMo4) in the T condition provides the necessary strength and fatigue resistance. Where a nitrided surface is specified for improved wear at the barrel interface, EN40B is the correct grade — delivering surface hardness that EN19 cannot achieve without distortion.
Pneumatic components typically operate at lower pressures than hydraulic systems, reducing the strength requirement. EN1A is ideal for cylinder end caps, ports, fittings and actuator parts produced on CNC lathes — the free-cutting properties reduce machining costs significantly on what are usually high-volume components.
Defence and aerospace applications demand premium grade steel with full traceability, 3.1 material test certificates, and consistent mechanical properties to tight specification windows. The same grades used in automotive drivetrain appear here — but to more exacting standards.
EN24T (817M40T / 34CrNiMo6 / AISI 4340) is one of the most widely specified materials in defence structural applications — used for aircraft undercarriage components, armoured vehicle drivetrain shafts and helicopter transmission shafts. Its nickel-chromium-molybdenum chemistry delivers the combination of very high tensile strength (up to 1150 N/mm²) and excellent impact toughness that safety-critical structural parts demand.
Aerospace and defence gearing demands the very highest combination of case hardness and core toughness. EN36 (14NiCr14) provides excellent performance for most applications. EN36C (832M13) adds molybdenum for the highest large-section core hardenability.
Structural fasteners for defence equipment require full mechanical certification, guaranteed tensile strength and impact values, and controlled hydrogen embrittlement resistance. EN19 (42CrMo4 / 4140) in the T condition satisfies Grade 10.9 and 12.9 strength levels. EN24T (4340) is specified where even higher strength or impact toughness is required per specific DEF STAN requirements.
Maintenance, repair and overhaul operations require fast access to the right grade — often as a single piece cut to a non-standard length — to get a production line or machine back running. Speed of supply and flexibility on quantity are the priorities.
The most common MRO requirement — a replacement shaft at a non-standard length, required today. EN8 in bright drawn round bar covers the majority of replacement shaft requirements for general plant and machinery. Where the original component was made from a higher grade, matching the grade is important — call our technical team and we will help identify the correct equivalent from the part markings or hardness reading.
Grey cast iron bar is the standard material for replacement bearing bushes, sleeves and journal liners in industrial machinery — its self-lubricating properties, vibration damping and machinability make it the natural like-for-like replacement for worn cast components.
Machine tool repair — spindles, lead screws, slideways — demands materials that can be hardened and finished to very tight tolerances without post-treatment distortion. EN40B (722M24) is used for nitrided spindles and precision shafts where the component must hold its ground dimensions after hardening.
Many maintenance engineering workshops hold small stocks of EN1A, EN3B and EN8 bright bar as general-purpose material for one-off repairs. Parkside supplies single-piece cut lengths with no minimum order — enabling workshops to replenish specific sizes without holding unnecessary stock. Call us for same-day cutting and next-day delivery on most sizes.
Which grades apply to which sectors — at a glance. ● Primary ∙ Suitable · Not typical.
| Grade | BS 970 | General Eng. | Automotive | Oil & Gas | Agriculture | Hydraulics | Defence | MRO | Data Sheet |
|---|---|---|---|---|---|---|---|---|---|
| EN1A | 230M07 | ● | ● | · | · | ● | · | ● | |
| EN3B | 070M20 | ● | · | · | ∙ | · | · | ● | |
| EN8 | 080M40 | ● | ∙ | · | ● | ∙ | · | ● | |
| EN9 | 070M55 | ∙ | · | · | ● | · | · | ∙ | |
| EN19 / 42CrMo4 | 708M40 | ● | ● | ● | ● | ● | ● | ● | |
| EN24T | 817M40T | ∙ | ● | ● | · | ∙ | ● | ∙ | |
| EN36 | 655M13 | ● | ● | · | ∙ | · | ● | · | |
| EN40B | 722M24 | ∙ | · | ● | · | ● | ∙ | ∙ | |
| 8620 / SAE 8620 | 805M20 | ● | ● | · | ∙ | · | ∙ | · | |
| Grey Cast Iron | EN-GJL-250 | ● | · | · | ● | · | · | ● | |
| S355 J2 | S355J2 | ∙ | · | ∙ | ∙ | · | · | ∙ |
Our sales team has been specifying steel grades for engineering applications since 1977. Tell us what you are making, what loads it carries and what heat treatment you intend — we will recommend the right grade and have it cut and on its way to you.