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Bolt Nut Fastener Force Conversion Table

Mechanical and Physical Properties of Carbon and Alloy Steel Bolts, Screws and Studs

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Use this table to determine tensile strength, yield strength, elongation at fracture, head soundness, notch impact strength and hardness of carbon and alloy bolts, screws and studs (coarse and fine thread).

According to EN ISO 898-1

Mechanical or Physical PropertyProperty Class
4.64.85.65.86.88.89.810.912.9/ 12.9
d ≤d > d ≤
16 mm a16 mm b16 mm
Tensile strength, Rm, MPanom.c40050060080090010001200
min.40042050052060080083090010401220
Lower yield strength, ReLd, MPanom.c240-300-------
min.240-300-------
Stress at 0,2 % non-proportional elongation, Rp0,2, MPanom.c-----6406407209001080
min.-----6406607209401100
Stress at 0,0048d non-proportional elongation for full-size fasteners, Rpf, Mpanom.c-320-400480-----
min.-340 e-420 e480 e-----
Stress under proof load, Spf, MPanom.225310280380440580600650830970
Proof strength ratio0,940,910,930,900,920,910,910,900,880,88
Sp,nom/ReL,min
or Sp,nom/Rp0,2 min or
Sp,nom/Rpf,min
Percentage elongation after fracture for machined test pieces, A, %min.22-20--12121098
Percentage reduction of area after fracture for machined test pieces, Z, %min.-52484844
Elongation after fracture for full-size fasteners, Af (see also Annex C)min.-0,24-0,220,20-----
Head soundnessNo fracture
Vickers hardness, HV F ≥ 98 Nmin.120130155160190250255290320385
max.220 g250320335360380435
Brinell hardness, HBW F = 30 D2min.114124147152181245250286316380
max.209 g238316331355375429
Rockwell hardness, HRBmin.6771798289-
max.95,0 g99,5-
Rockwell hardness, HRCmin.-2223283239
max.-3234373944
Surface hardness, HV 0,3max.--390435
Non-carburization, HV 0,3max.-hhh
Height of non-decarburized thread zone, E, mmmin.-1/2 H12/3 H13/4 H1
Depth of complete decarburization in the thread, G, mmmax.-15
Reduction of hardness after retempering, HVmax.-20
Breaking torque, MB, Nmmin.-in accordance with ISO 898-7
Impact strength, KV i j, Jmin.-27-27272727k
Surface integrity in accordance withISO 6157-1lISO 6157-3

a Values do not apply to structural bolting.

b For structural bolting d ≥ M12.

c Nominal values are specified only for the purpose of the designation system for property classes. See Clause 5.

d In cases where the lower yield strength, ReL, cannot be determined, it is permissible to measure the stress at 0,2 % non-proportional elongation Rp0,2.

e For the property classes 4.8, 5.8 and 6.8, the values for Rpf,min are under investigation. The values at the time of publication of this part of ISO 898 are given for calculation of the proof stress ratio only. They are not test values.

f Proof loads are specified in Tables 5 and 7.

g Hardness determined at the end of a fastener shall be 250 HV, 238 HB or 99,5 HRB maximum.

h Surface hardness shall not be more than 30 Vickers points above the measured base metal hardness of the fastener when determination of both surface hardness and base metal hardness are carried out with HV 0,3 (see 9.11).

i Values are determined at a test temperature of −20 °C (see 9.14).

j Applies to d ≥ 16 mm.

k Value for KV is under investigation.

l Instead of ISO 6157-1, ISO 6157-3 may apply by agreement between the manufacturer and the purchaser.

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