🔩 Mechanical properties of bolts, screws and studs made of carbon steel and alloy steel — property classes 4.6 to 12.9: tensile strength, yield strength, stress under proof load, elongation, hardness; PN-EN ISO 898-1

Materials and NDT PN-EN ISO 898-1

Overview

WHAT THE STANDARD COVERS. ISO 898-1:2013 (clause 1) specifies the mechanical and physical properties of bolts, screws and studs (together: fasteners) made of carbon steel and alloy steel, tested at an ambient temperature of 10 °C to 35 °C. Fasteners conforming to the standard are evaluated in this temperature range — at elevated (Annex B) and/or lower temperatures they might not retain the specified properties. Note 1 of the standard: such fasteners are used from −50 °C to +150 °C; outside this range, up to +300 °C, consulting an experienced fastener metallurgist is advised. Certain bolts and screws — with a low or countersunk head — might not fulfil the tensile or torsional requirements, because the head geometry reduces the shear area in the head compared with the stress area in the thread (point 8.2). The standard applies to products of carbon steel or alloy steel with triangular ISO metric screw thread in accordance with ISO 68-1, with coarse pitch thread M1,6–M39 and fine pitch thread M8×1–M39×3, with diameter/pitch combinations in accordance with ISO 261 and ISO 262 and thread tolerances in accordance with ISO 965-1, ISO 965-2 and ISO 965-4. It does not apply to set screws and similar threaded fasteners not under tensile stress (ISO 898-5). It does not specify requirements for weldability, corrosion resistance, resistance to shear stress, torque/clamp force performance (test method: ISO 16047) or fatigue resistance. The “Scope” field of the PKN card of PN-EN ISO 898-1:2013-06 (English version, scope description in Polish), excerpt in our translation: “This part of ISO 898 specifies the mechanical and physical properties of bolts, screws and threaded studs made of carbon steel and alloy steel tested at an ambient temperature in the range from 10 °C to 35 °C.”

DESIGNATION SYSTEM FOR PROPERTY CLASSES (clause 5). The symbol consists of two numbers separated by a dot. The number to the left (one or two digits) is 1/100 of the nominal tensile strength Rm,nom in MPa. The number to the right is ten times the ratio of the nominal yield strength to Rm,nom: .6 → 0,6, .8 → 0,8, .9 → 0,9; the nominal yield strength is the lower yield strength ReL,nom, the stress at 0,2 % non-proportional elongation Rp0,2 nom or the stress at 0,0048d non-proportional elongation for the full-size fastener Rpf,nom. The product of both values gives the nominal yield strength in MPa. An additional zero before the property class designation indicates a fastener with reduced loadability — the standard’s example: a product with the material properties of class 8.8 but with reduced loadability is designated 08.8. The system may also be applied to sizes outside the standard (e.g. d > 39 mm), provided all requirements of Tables 2 and 3 are met.

MATERIALS (clause 6, Table 2). Classes 4.6–6.8: carbon steel or carbon steel with additives, with no specified tempering temperature (for cold forged classes 4.6 and 5.6, heat treatment of the wire or of the finished product may be necessary to achieve the required ductility; in classes 4.6, 4.8, 5.8 and 6.8 free cutting steel with S up to 0,34 %, P up to 0,11 % and Pb up to 0,35 % is allowed). Classes 8.8, 9.8 and 10.9: carbon steel with additives (e.g. B, Mn or Cr), carbon steel or alloy steel — quenched and tempered; minimum tempering temperature 425 °C, P and S at most 0,025 %, B at most 0,003 % (up to 0,005 % if non-effective boron is controlled by the addition of titanium and/or aluminium). Class 12.9: quenched and tempered alloy steel (C 0,30–0,50 %, tempering at least 425 °C) or quenched and tempered carbon steel with additives (e.g. B, Mn, Cr or Mo) (C 0,28–0,50 %, tempering at least 380 °C). For classes from 8.8 upwards the material must have a hardenability ensuring approximately 90 % martensite in the core of the threaded section in the as-hardened condition, before tempering. In class 12.9, products made of phosphated raw material shall be dephosphated before heat treatment, and the standard advises caution when choosing this class — the environment can cause stress corrosion cracking of the products, coated ones included. For hot dip galvanized fasteners the additional requirements of ISO 10684 apply.

PROPERTIES (clause 7, Table 3). Fasteners of each class shall, at ambient temperature, meet all applicable requirements of Tables 3–7, regardless of which tests were performed during manufacturing or final inspection. Minimum tensile strength Rm: 4.6 — 400 MPa, 4.8 — 420, 5.6 — 500, 5.8 — 520, 6.8 — 600, 8.8 — 800 (d ≤ 16 mm) and 830 (d > 16 mm), 9.8 — 900, 10.9 — 1040, 12.9 — 1220 MPa. Minimum stress at 0,2 % non-proportional elongation Rp0,2: 8.8 — 640/660, 9.8 — 720, 10.9 — 940, 12.9 — 1100 MPa. Nominal stress under proof load Sp: from 225 MPa (4.6) to 970 MPa (12.9), e.g. 8.8 — 580/600, 10.9 — 830 MPa. Minimum percentage elongation after fracture of the machined test piece A: 4.6 — 22 %, 5.6 — 20 %, 8.8 — 12 %, 9.8 — 10 %, 10.9 — 9 %, 12.9 — 8 %; reduction of area Z: 8.8 — 52 %, 9.8 and 10.9 — 48 %, 12.9 — 44 %. Vickers hardness HV (F ≥ 98 N) — minimum from 120 (4.6) to 385 (12.9), maximum e.g. 435 HV in class 12.9; the table also gives Brinell hardness (F = 30 D²) and Rockwell HRB/HRC (e.g. 10.9: 32–39 HRC). The head shall not fracture in the head soundness test. The values of the “d ≤ 16 mm” column of class 8.8 do not apply to structural bolting — for it the “d > 16 mm” column applies already from M12 (footnotes a and b). Impact strength of machined test pieces is tested at −20 °C (footnote 2 to clause 7, point 9.14); the requirement applies to d ≥ 16 mm, and for class 12.9 the value is under investigation. Footnote e: the Rpf,min values for classes 4.8, 5.8 and 6.8 “are under investigation” and serve only for calculating the ratio Sp,nom/Rpf,min — they are not test values.

LOADS (Tables 4–6). Minimum ultimate tensile load Fm,min = As,nom × Rm,min and proof load Fp = As,nom × Sp,nom, where As,nom is the nominal stress area in the thread. Examples for coarse thread: M12 (84,3 mm²) in class 8.8 — Fm,min 67 400 N, Fp 48 900 N; M20 (245 mm²) in class 10.9 — Fm,min 255 000 N, Fp 203 000 N. For structural bolting, Tables 4 and 5 give separate class 8.8 values for M12, M14 and M16 (e.g. M12: Fm,min 70 000 N, Fp 50 700 N), and for threads with tolerance 6az subject to hot dip galvanizing — reduced values in accordance with ISO 10684:2004, Annex A. Table 6 gives the minimum ultimate tensile loads for fine pitch thread (e.g. M8×1: 39,2 mm²).

TEST METHODS (clauses 8–9 — titles from the table of contents only). Clause 8 sets out which tests can be performed for the various groups of fasteners and machined test pieces, including loadability (8.2) and the manufacturer’s, supplier’s and purchaser’s tests. Clause 9 covers, among others: the tensile test under wedge loading of finished bolts and screws (9.1), the tensile test for determination of Rm (9.2), the determination of elongation Af and stress Rpf of full-size fasteners (9.3), tensile tests of products with reduced loadability due to head design (9.4) and with waisted shank (9.5), the proof load test (9.6), the tensile test of machined test pieces (9.7), the head soundness test (9.8), hardness (9.9), decarburization (9.10), carburization (9.11), retempering (9.12), torsion (9.13), impact of machined test pieces (9.14) and surface discontinuity inspection (9.15); clause 10 — marking. The normative references include, among others, ISO 6892-1 (tensile testing), ISO 6506-1, ISO 6507-1 and ISO 6508-1 (Brinell, Vickers, Rockwell hardness), ISO 148-1 (Charpy), ISO 7500-1 (verification of testing machines) and ISO 6157-1 and -3 (surface discontinuities).

EDITION. The fifth edition ISO 898-1:2013 (ISO/TC 2/SC 11) cancelled and replaced the fourth edition ISO 898-1:2009, of which it is a minor revision. In the iTeh catalogue (read on 28.10.2026) ISO 898-1:2013 has the status “Published” and the stage “9092 – International Standard to be revised”; next to it is the corrigendum EN ISO 898-1:2013/AC:2013 (= ISO 898-1:2013/Cor 1:2013), which does not appear in the PKN search results (search term “ISO 898-1”). The corrigendum replaces line 11 of Table 3 — Brinell hardness, with corrected values for classes 8.8, 9.8, 10.9 and 12.9 — and according to its title page it became effective on 9 October 2013 for the official French version of the EN; in the English text we read, line 11 already has exactly these values.

STATUS (PKN card as of 28.10.2026). The card of PN-EN ISO 898-1:2013-06 (English version) has no withdrawal label: publication 07-06-2013, 68 pages, Machinery and Engineering Sector, KT 236 Fasteners and Assembly Tools, “Adopts: EN ISO 898-1:2013 [IDT], ISO 898-1:2013 [IDT]”, “Replaces: PN-EN ISO 898-1:2009 - English version, PN-EN ISO 898-1:2009 - German version”, ICS 21.060.10; the card has no “Directive” or “Mandate” fields. PKN search, search term “ISO 898-1” (27.10.2026): next to it are the withdrawn PN-EN ISO 898-1:2001 (Polish version) and PN-EN ISO 898-1:2009 (English and German versions); there is no Polish version of the 2013 edition in the results.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database refreshed from the production server on 27.10.2026 and current PCA documents). Number 898-1 appears in 9 records at 6 Polish laboratories: AB 005 (two records — Polish and English version of the same entry), AB 023 (two), AB 128, AB 342, AB 490, AB 1615 (two). In the current PCA documents of these 6 laboratories the standard occurs 9 times in total — as many as in the copy; no entry is suspended. Notations: “PN-EN ISO 898-1:2013-06” (AB 342, AB 490; AB 1615 with a point — “pkt 9.2” for tensile strength and “pkt 9.9” for hardness) and “PN-EN ISO 898-1” without a year (AB 005, AB 023, AB 128). Standards cited in the same entries: PN-EN ISO 6892-1:2020-05 method B (AB 342, AB 490, AB 1615), PN-EN ISO 6507-1:2024-04 (AB 1615), PN-EN ISO 898-2 (AB 005, AB 128, AB 490), PN-EN ISO 3506-1 (AB 023, AB 342), PN-EN 28839 and PN-EN ISO 2320 (AB 128), PN-G-15026:2017-04 and DIN 21530-4:2003 (AB 005). The “Laboratories” tab (“PN-EN ISO 898-1”) shows 10 laboratories: these 6 Polish ones and 4 Czech ones (query of the tab on labcoda.pl, 28.10.2026).

WHAT THE LABORATORIES TEST (database copy and PCA documents, complete entries). Mechanical properties of fasteners by the tensile method: metal fasteners (AB 128 — together with PN-EN 28839, PN-EN ISO 898-2 and PN-EN ISO 2320), bolts and nuts (AB 490 — with PN-EN ISO 6892-1 method B and PN-EN ISO 898-2), steels, non-ferrous metals and their alloys after various treatments as well as bolts and studs — Rp, Re, Rm, A, Z, F at loads up to 350 kN, tensile test at room temperature (AB 342 — with PN-EN ISO 6892-1 method B and PN-EN ISO 3506-1); fasteners — tensile strength Rm at forces up to 50 kN (AB 1615, point 9.2 with PN-EN ISO 6892-1 method B) and HV10 hardness by the Vickers method (AB 1615, point 9.9 with PN-EN ISO 6507-1); metal anchors — expansion, driven, screwed and bonded — load capacity of threaded anchors in a tensile test of 1–1000 kN (AB 023, together with PN-EN ISO 3506-1); clamps and joints of arch supports made of channel sections — in the same entry, among others, resistance to proof load of full-size bolts, nuts and hook bolts at forces up to 1000 kN (AB 005, together with PN-G-15026:2017-04, DIN 21530-4:2003 and PN-EN ISO 898-2).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. First — temperature: the requirements apply to tests at 10–35 °C (exception: impact strength — at −20 °C); properties at other temperatures are not covered by them. Second — diameter and purpose: in class 8.8 the values for d ≤ 16 mm and d > 16 mm differ (Rm 800 and 830 MPa, Rp0,2 640 and 660 MPa), for structural bolting the d > 16 mm column applies already from M12, and the load tables have separate M12–M16 values for it — using the general row gives a false conformity. Third — the table: coarse thread (Tables 4 and 5) and fine pitch thread (Table 6) have different stress areas, and 6az thread for hot dip galvanizing — values reduced in accordance with ISO 10684. Fourth — reduced loadability: a product with a low or countersunk head or a waisted shank (designation with a zero, e.g. 08.8) is tested by other tests (9.4, 9.5) and must not be assessed against the requirements of full loadability. Fifth — the Rpf,min values of classes 4.8, 5.8 and 6.8 are not test criteria (footnote e). Sixth — in an entry with PN-EN ISO 3506-1 (stainless steel fasteners) the report must state by which standard the result was assessed, because ISO 898-1 covers only carbon steel and alloy steel.

WHAT WE DO NOT GIVE. The fragment of ISO 898-1:2013 we read ends with Table 6 (clause 7). We do not give Table 7 (proof loads for fine pitch thread), the course of the test methods (clauses 8–9 — we know only their titles from the table of contents), marking (clause 10) or Annexes A–C. We did not check references to the standard in legislation.

Method principle

The properties of fasteners are determined by the tests specified in clause 9 of the standard — among others by a tensile test of the finished bolt (also with a wedge — point 9.1) or of a machined test piece, a proof load test and hardness measurement — and the result is compared with the requirements of the property class: minimum tensile strength Rm, yield strength, stress under proof load Sp, elongation and hardness (Table 3), and with the minimum ultimate tensile load Fm,min = As,nom × Rm,min and the proof load Fp = As,nom × Sp,nom for the given thread (Tables 4–6; ISO 898-1:2013, clauses 5–9).

Applications

• Bolts, screws and studs of carbon steel and alloy steel, ISO metric coarse thread M1,6–M39 and fine pitch thread M8×1–M39×3 (ISO 898-1:2013, clause 1)
• Assessment of conformity with property class 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9 and 12.9 (also of products with reduced loadability, e.g. 08.8)
• In accreditation scopes: metal expansion, driven, screwed and bonded anchors; full-size bolts, nuts and hook bolts of arch support joints made of channel sections; metal fasteners, bolts and nuts
• In accreditation scopes: 6 Polish laboratories — tensile tests up to 50, 350 and 1000 kN, HV10 hardness

Key parameters

Standard

Standard number

PN-EN ISO 898-1:2013-06 (wersja angielska; wprowadza EN ISO 898-1:2013 i ISO 898-1:2013 [IDT])

Title (PL)

Własności mechaniczne części złącznych wykonanych ze stali węglowej oraz stopowej — Część 1: Śruby i śruby dwustronne o określonych klasach własności — Gwint zwykły i drobnozwojny

Title (EN)

Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and studs with specified property classes — Coarse thread and fine pitch thread

Step-by-step procedure

1. Identifying the product and class

   Thread (coarse or fine pitch), diameter, property class and whether the product has full or reduced loadability (designation with a zero); choice of the tests feasible for the given group (clause 8 — title).

2. Tests

   Tests of clause 9 appropriate for the product, e.g. tensile test for determination of Rm (9.2), proof load (9.6), hardness (9.9) — at an ambient temperature of 10–35 °C.

3. Assessment

   Comparison with Table 3 (the row for the relevant diameter) and with Fm,min and Fp from Tables 4–6 for the given thread.

4. Result

   Conformity with the property class, stating the standards and points by which the testing was done. PN-EN ISO 898-1:2013-06 — current (PKN card as of 28.10.2026; English version).

Required equipment and apparatus

Health and safety (OHS)

• TECHNICAL NOTE: the requirements apply to tests at 10–35 °C; properties at other temperatures are not covered by them
• TECHNICAL NOTE: a product with reduced loadability (e.g. 08.8) is not assessed against the requirements of full loadability
• Breaking tests of bolts at high forces (up to 1000 kN in the scopes) — machine guards and a safety zone

Frequently asked questions