EN8 vs EN8D Steel Tubes: What Is the Difference and Which One to Use

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EN8 and EN8D steel tubes are medium-carbon steel products used for components requiring strength, machinability, and wear resistance. The difference is that ordering for EN8 is typically by the mechanical properties of the material (EN8 080M40) and is typically by chemical composition under the relevant BS 970 ordering designation (EN8D 080A42). These two are suitable for machining shafts, sleeves, bushes, spacers and many other engineering components; however, none of these can be regarded as free-cutting steel.Choose EN8 when the drawing needs a guaranteed tensile band. Choose EN8D if you require precision of chemical control and size drawn. The following paper gives a comparison of properties of EN8D, its composition, machinability, equivalent BS 970, and automotive applications.

Quick Comparisons Between EN8 vs EN8D 

Both grades are medium carbon steels from the old British standard BS 970, and on paper they look almost the same. The practical difference is in what the standard promises you. EN8 comes with mechanical values for stated conditions. EN8D comes with a tighter chemical analysis and no guaranteed mechanical values.

Factor	EN8 (080M40)	EN8D (080A42)
BS 970 Designation Letter	M: Ordered to mechanical properties	A: Ordered to chemical composition
Carbon Content	0.36–0.44%	0.40–0.45%
Manganese Content	0.60–1.00%	0.70–0.90%
Guaranteed Property	Tensile strength in stated condition (R, S, T, or U)	Chemical analysis (no guaranteed mechanical values)
Commonly Supplied As	Hot rolled, normalised, or heat-treated bar and tube	Bright drawn, peeled, or ground bar and hollow bar
Free-Cutting Variant?	No (EN8M is the free-machining variant)	No (EN8DM is the free-machining variant)
Nearest EN 10083-2 Grade	C40 / C45	C45 / C45E

What do EN8 and EN8D mean?

BS 970 describes a steel with a six-character code, and each part tells you something. Take 080A42 (EN8D) and 080M40 (EN8):

• First three digits: 100 times the mean manganese content. 080 means a mean of 0.80% manganese, so both grades sit in the same manganese family. EN8D narrows the window to 0.70–0.90%.
• The letter: A means ordered to composition (analysis). M means ordered to mechanical properties. H means ordered to hardenability, and S means stainless.
• Last two digits: 100 times the mean carbon content. 40 means about 0.40% carbon and 42 means about 0.42%.

So 080M40 (EN8) is a steel you buy for its strength in a stated condition, and 080A42 (EN8D) is a steel you buy for its chemistry. That single letter explains most of the differences in the sections below.

What BS 970 is today. BS 970 has been superseded in Europe by the BS EN 10083 series, so it is best described as BS 970 (withdrawn, still used in trade). Drawings, enquiries and stockists still use EN8 and EN8D every day, which is why we list the nearest EN 10083-2 grades in the equivalent-grade table below.

EN8D Composition Compared With EN8

Element	EN8 (080M40)	EN8D (080A42)
Carbon (C)	0.36–0.44	0.40–0.45
Silicon (Si)	0.10–0.40	0.10–0.40
Manganese (Mn)	0.60–1.00	0.70–0.90
Phosphorus (P), max	0.050	0.050
Sulphur (S), max	0.050	0.050

EN8D Properties and EN8 Mechanical Conditions

EN8 Condition (BS 970)	Tensile Strength (MPa)	Where EN8D Stands
R	550–700	No guaranteed value; depends on bar condition and size
S	625–775	As above
T	700–850	As above
U	775–925	As above

EN8D Equivalent Grades

BS 970 Grade	EN 10083-2	AISI / SAE	Other
EN8 (080M40)	C40 / C45	1040–1045	Werkstoff 1.0511 / 1.0503
EN8D (080A42)	C45 / C45E	1045 (1042–1045)	S45C (JIS)

Heat treatment and welding of EN8 and EN8D

Both grades respond to the same heat treatments. Section size limits how deeply they harden, so check the core strength of thick parts rather than assuming the surface result.

Process	Typical Range	Note
Annealing	680–720 °C, slow furnace cool	Softens for heavy machining
Normalising	830–860 °C, air cool	Refines grain and evens out properties
Hardening	820–860 °C, oil or water quench	Section size limits through-hardening; check core strength
Tempering	550–660 °C	Sets final strength; soak time depends on section
Welding	Preheat is normally needed; a typical range for this carbon content is 150–250 °C, set by a qualified welding procedure	Medium carbon content raises cracking risk; follow a qualified procedure
Induction hardening	Suitable, subject to geometry and required case depth	Both grades; confirm with the heat treater

EN8D automotive applications and other uses

EN8 and EN8D have almost the same chemistry and end up in similar parts, because both give medium strength with good fatigue behaviour once hardened and tempered.

Application	Usually Specified	Why
Drive and transmission shafts	EN8 or EN8D	Strength after heat treatment; EN8D bright stock arrives straight and sized
Axle parts, spindles, studs, pins	EN8 or EN8D	Medium strength with good fatigue behaviour once tempered
Sleeves, bushes, spacers (tube form)	EN8D hollow bar / CDS tube	Consistent drawn stock cuts with little waste
Gears, couplings, keys	EN8	Normalised or Q / R condition with a stated tensile band
Hydraulic and machinery components	EN8D drawn stock	Tight size reduces stock removal

Which one to use: EN8 or EN8D

Your Requirement	Choose	Check First
Drawing says EN8 or 080M40	EN8 in the stated condition	No swap without design approval
Drawing says EN8D or 080A42	EN8D; confirm bright, peeled or ground	Delivery condition and tolerance
Need a guaranteed tensile band	EN8 in R, S, T or U condition	Ruling section and condition letter
Need consistent drawn size and finish	EN8D	Straightness and OD tolerance
Fast machining is the priority	EN8M / EN8DM (where drawing allows)	Impact toughness, sulphur level
Large section, high core strength	Move to alloy steel (EN19 / EN24, 4140 / 4340)	Hardenability and section size

When neither EN8 nor EN8D is enough

For large sections, high core strength or heavy shock loading, medium carbon steel runs out of hardenability. The usual step up is alloy steel such as EN19 (AISI 4140) or EN24 (AISI 4340). See our 4140 alloy tubing, AISI 4340 tubes and alloy steel tubes, or read alloy steel vs carbon steel for a plain comparison. For everyday medium carbon needs, browse our carbon steel pipes and tubes.