INTERNATIONAL STANDARD ISO

ISO
INTERNATIONAL
STANDARD
898-2
Second edition
1992-11-01
-ce-p-- --.._
- ________
------.--Y----P
- _^._
--._-
__---
_______
Mechanical
__
_-_.--
_--__.-..-
-----
properties
--
-0-------
---
of fasteners
proof load values
Caract&-istiques
des t%ments
2: Eo-aus
Partie
avec charges
d’i+renve
.--0
-
Part 2:
Nuts with specified
thread
rmkxniqrres
-Pp
de fixatim
specifi6es
- Coarse
--
Filetages
2 pas
CJI-OS
--__I~._~~---I--- _____-__-------
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-----
___-__
--.----.----
--~
~
_-_-_
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---
-..--_e------
---__-_--_-
____
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--
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-------
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._
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-_.
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--
_
_
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_
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--=
Refcrence
numbcr
ISO 898-2: 19921 E)
ISO 898-2:1992(E)
Fsreword
ISO (the International
Organization
for Standardization)
is a worldwide
federation
of national Standards bodies (ISO metnber bodies). The work
of preparing
International
Standards
is normally
carried out through ISO
technical
comtniZZees.
Esch tnember
body interested
in a subjed: for
which a technicat
commitlee
has been established
has Zhe right 90 be
represented
on that cotnmittee.
International
organizations,
governmental and non-govet-nmental,
in liaison with ISO, also take part in the
work. lS0 cotlaborates
ctosely with the International
Electrotechnical
Commission
(IEC) on alt mattet-s of etectrotechnicat
standardization.
Draft lntet-national
Standards
adapted by Iahe techllical
cotm-nittees
at-e
circutated
to the member
bedies for voting.
Publication
as an tnternationat
Standard
r-equires approvat
by at least 75 94 of the member
bodies casting a vote.
International
Standard
ISO/TC 2, Fasfeners,
Tasfeners.
This
(ISO
second
edition
898-2:1980), which
ISO 898-2 was prepared
by Technical
Committee
Sub-Committee
SC 1, Mechanicai
properfies
of
the
cancels
and
replaces
has been technicalty
revised.
ISO 898 consists of ,the fotlowinq . parls,
ical proper-fies
of I;r--asfeners:
screws
the general
_I
Part
--
Part 2; Nufs wifh specified
-
Part 5: Set screws
siresses
-
Part 6: Abts
-
fest ai ld minimum
Part 7: Torsioriai
torques
with nominal dianiete/-s I mm to 10 mm
Annexes
1: Belts,
under
fit-st
edition
titte MecI~a1)-
arM studs
proof
and similar
with specilred
Load values
threaded
proof
-- Coarse
fasteriers
Load vahes
fhread
not- under
- Fine pifch
for bolts
A and B of Ibis pst-t of ISO 898 are for infortnation
t ensile
thread
and screws
only.
0 ISO 1992
All rights reserved. No part of this publication may be t-cproduced or utilized in any form
or by any means, electt onic or mechanical, i~~cluding photocopying and microfiltn, without
permission in writing from the publisiter-.
Internalional Orgat~ization for Standard ization
Case Postale 56 * CH-1211 Genkve 20 * Switzer land
Pr inteci in Switzerlatid
ii
INTERNATIONAL
STANDARD
MechanicaII
ISO 898-2:1992(E)
properties
of fasteners
-
Part 2:
NUSSwith specified proof load values - Coarse thread
1
--- corrosion
Scope
This international
Standard specifies the mechanicai
properties
of nuts with specified
proof Load values
when tcsted at room temperature
(sce ISO 1). Properties will Var-y at higher and lower temperature.
It applies
--
-
--
ability
to
with nominai
i ng 39 mm;
Ihrcad
diameters
up to and incIud-
temperatures
withstand
- 50 OC.
with diameter/pifch
combinations
ISO 261 (coarse thread);
--- with thread tolerantes
and ISO 965-2;
--
with
I_
with widths across
or equivalenl;
according
6H according
mechanical
to
to ISO 965-1
2
For special
-
-
with nominal
O,W*‘;
made
of carbon
heights
free-cutting
products
bolting,
such
abiliiies
1) is the nominal
as specified
see the
3 For assemhlies
than 6H/6g, there
also table 1.
with threads
having
is an increased
risk
high-strength
product
Standards
greater
than
Reduction
tolerantes
wider
of stripping;
see
in thread strength
in ISO 272
or equal
to
Test load, 74
greater
than
Thread tolerantes
less than or
equal to
-_
steel.
special
properties
(sec ISO 2320);
of the internal
thread
in accordance
for
4 In the case of thread tolerantes
other or larger than
6t-1, a decrease
of the stripping
strength
should be considered (see table 1).
Thread
steel or low alloy
diameter
for
nuts for use with hot-
boits,
--- weldability;
‘)
as nuts
not be used
reguirements;
It does not appfy to nuts requiring
such as
lackirig
should
dipped galvanized
appropriate
values.
M2,5
.--
--
steel
and overtapped
Table 1 flats
a bove
NOTES
structural
of trianguIar
ISO thread and with diameters
and
pitches according . to ISO 68 and ISO 262 (coarse
thread);
(see ISO 3506);
--t--300 OC or below
1 Nuts made from
above -+ 250 “C.
to nuts
specific
-
resistance
with ISO 724.
6H
7H
6G
100
--
95,5
1.--.-
ISO 898-2:1992(E)
2
Normative
ISO 6507-1: 1982, Mefallic
n-,aterials ---- Hardness
- Vickers test -- Part 1: HV 5 to 1-N 100.
references
The foIiowing
Standards
contain
provisions
which,
through
reference
in this text, constitute
provisions
of this par-t af ISO 898, At the tirne of publicaiion,
the
editions
indicated
were valid.
All Standards
are
subject to revision, and Parties to agreements
based
on this part of 1SO 898 are encouraged
to investigate
the possibility
of applying
the most recent editions
of the Standards
indicated
below. Members
of IEC
and ISO maintain
registers
of currently
valid International Standards.
ISO 1:1975, Siandard
refereuce
dustrial length measrIrernerIts.
ISO 68:1973,
Basic Profile.
ISO general
/lur/lose
1SO 272:1982,
Widths across
screw
purpose
ISO 261:1973,
ISO qeneral
fhreads - General i/an.
ISO 262:1973,
ISO
threads -- Seiected
iemperafrrre
for in-
fhreads
metric
-
screw
general
purpose
metric
screw
sizes for screws, bolts and nuts.
FasteIlers
flats.
-
Hexagon
prodlrcts
--
ISO 286-2:1988,
ISO System
of Limits and fits Part 2: 7ables of Standard tolerante
grades and limit
deviations
for holes and shafls.
’
ISO 724:1978,
mensions.
ISO mefric
screw
ISO 965-1:1980,
ISO general
threads -- Polerances
--- Part
data.
threads
-
Basic
di-
purpose
metric
screw
1; Frinciples
and basic
1SO 965-2:1980,
ISO yeneral
purpose
tnetric screw
threads ---. Tolerallces
- Parf 2: Limits of sizes for
generai
purpose
holt and nuf thr,eads -- Mediwn
quality.
test
ISO 6508:1986, Metallic
rnaterials -- Hardness
fest -Rockwell
fest (scales A - 8 - C - D - E - F - G - H 0
3
Designation
System
3.1 Nuts with nominal heights > 0,811
(effective lengths af thread > 0,6/))
Nuts with nominal
heights > 0,811 (effective
lenqths
of thread > 0,6D) are designated
by a nur-&&
to
indicate the maximum
appropriate
pt-operty class of
bolts with which they may be mated.
Failure of threaded
fasteners
due to over-tightening
tan occur by bolt shank fracture or by stt-ipping of
the threads of the nut and/or bolt. Shank fracture is
sudden
and therefore
easily
noticed.
Stripping
is
gradual
and therefore
difficult to detect and this introduces
the danger of partly failed fasteners
being
left in assemblies.
lt would therefore
be desirable
to design thr-eaded
connections
so that their mode of failure would always be by shank fracture
but, unfortunateIy,
beCause of the many variables
which govern stripping
strength
(nut and bolt mate+!
r,trzngths,
thread
etc.),
11uts
across-flats
dimensions,
clearances,
would have to be objectionably
thick to guarantee
this mode in atl cases.
A bolt or screw of thread M5 to M39 assembled
with
a nut of the appropriate
propet-ty class, in accordancc with tabte 2, is intended
to provide
an assembly capable of beirigg tightened
to the holt proof
load without thread stripping
occurring.
--- Surface discontincrities
ISO 6157-2:--- l) , Fasteners
- Part 2r Nuts with threads MIS to M39.
However,
should tiqhtening
beyond bolt proof load
take place, the nut‘design
is intended
to ensure at
least IO % of the over-tiqhtened
asscmblies
fail
through bolt breakage
in Order to warn the User that
the installation
practice is not appropriate.
ISO 6506: 1981, Mefallic
Brinell test.
of screw
ISO 4964: 1984, Steel -- Hardness
1)
2
7-o be published.
rnaterials
conversious.
-
Hardrjess
test --
NOTE 5
For more detailed
thrcad assemblies,
information
on the strength
see annex A.
ISO 898=2:1992(E)
Table
2
- Designation
System for nuts with nominal
heights > 0,811
Mating bolts
Property
class of
nut
Property cfass
Property class of
nut
4
---_----.
5
3.6: 4.6; 4.8
-_-_---..
3.6; 4.6; 4.0
.------_I-5.0
-----
6
------_---8
6.8
--.--_-.--c- ----.--
and Stresses under
heights 2 0,5D but
9
Nominal stress
under proof load
Actual stress
under proof load
Nimm*
N/mm*
04
5.6;
.-_-.__I_
System
nominal
< 0,8D
Thread ranges
---
Table 3 - Designation
proof load for nuts with
> M16
>- M 16
---- --.~-.-- - ---<; M16
.~XII___
< M39
< M39
-.
----~-._---< M39
< M39
.------.-.-----___-._-----~
400
---~-------_---,
-500
05
~--
380
-
500
.-.-
8.8
----
4
Materials
Nuts shall be made
Chemical composition
9
_--_-_
10
--------__
12
------.
N0-T‘F..
Table
4 -
of steel conforming
to the
limits specified
in table 4.
Limits of Chemical composition
Chemical cotnposition
litnits
Property ctass
In yeneral,
nuts of a higher- property
class tan t-eplace nuts of a Iower property
class. This is advisable
for a
bolt/nut
assernbly
going it-tto a stress
hicj-Ier than the yield
st.ress or the stress under proof load.
___---~._je 2)
3.2 Nuts with ncxr~inal heights > 0,511 hut
< 0,811 (effective heights of thread > 0,W but
< 0,611)
Nuts with nominal
heiqhts 2 0,51) but c 0,811 (effective height of thread 5 0,4D but c 0,6/1) are designated by a combination
of two numbers:
the second
itrdicalcs
the nominal
stress under proof load on a
hardened
test mandrei,
while the fit-st inclicates that
the loadability
of a bolt-nut assembly is reduced in
comparison
with the loadability
on a hardened
test
mandrel
and also in cotnparison
with a bolt-nut assembly
described
in 3.1. The effective
loading
capacity is not only detcrmincd
by the hardness of the
nut and the effective height of thread but also by the
tensile strength of the holt with which the nut is assembled.
Table 3 gives the designation
System and
the Stresses
under proof Ioad of the nuts. Proof
loads arc shown in table 6. A guide fot- minimum
expected
stripping
strengths
of the joints
when
these nuts arc assembled
wif.h bolts of vat-ious
property classes is shown in table 7.
---
;
~_
05 i,
j
-_
0,58
j
I
____^
0,30 /
O&+iii--
I
I
1) Nuts of these proper-ty classes may be manufactured
from ft’ee-cuttiny steel unless otherwise agreed between the
purchaser and the tnanufacturet-. In such cases, the following
maximutn Sulfur, phosphorus and Icad contents at-e perrnissible:
sulfur 0,34 74; phosphorus
0,ll
%; Iead 0,35 %.
2) Alloying elements may be added, if necessary,
velop the mechanical properties of the nuts.
Nuts of property
classes 05, 8 (style 1 above
10 and 12 shall be hardened
and tempered.
5
Mechanical
to de-
M16),
properties
When tested by the methods
described
in clause 8,
ihe nuts shall have the mechanical
properties
set
out in table 5.
i
I
/
1
IM7
1 MIO
//Y-+i-
I
i
~4
I
I
/
-
greater
than
Nil0
MIO
M7
M4
less
/
’ than or
equal to
Thread
PA7
greater
than
j
1
:
1:
t
T
f
1
+
1
I
j
!
t
i
lI
i
;
i
1
f
1
4
1
i
11 iess
i
1
1 than or [
j eaual to I
l
Thread
I
1
1
I
1
630
610
530
580
520
N/mm2
%
Stress
under
proof
load
380
N/mm2
%
S tress
under
proof
ioad
1
t
Ll
t
/
1--r
1 130
1
min.
max.
l
1 302
I
i
?1
1
I Vickers
l hardness
HV
!
l
I
5 3)
188
min.
i
1
I
i
I
i
i
II
i
9
t
1
I
1
1
I
Nut
NQTA)
state
302
max.
Vickers
hardness
HV
04
i
l
1I
/
1
NQTif
state
/
thin
style
680
Nimm2
sP
Stress
under
proof
load
720
höö-
I
i
i
II
/
i
Nut
i
T
I
j
/
/
1
7
1I
I
I
j
1
I
!
Il
I
i
ij
I
/ 202
l(
l
I
L
/
L
170 1
I
!50
I
353
NQ1 ‘11 1
1
class
I
I
I
I
j
i,
l
1
i1
/
Il
I
Nt’mm2
i 300
lt
l 855
l- 370
t 880
1
r
I
%
proof
Joad
thin
style
1
l
I1
353 j
1
Vickers
hardness
I-W
!(
1
I
Nut
i
il
i
1 233
L
ii
i
J
QT2)
state
t
1Stress
under
Property
’
1
i
i style
Nut
272
,
l
l
I
I
max.
Vickers
hardness
I-W
1
l
l
Ii
.mm.
F
/
Il
T
1
min. , max. j state
!
/
t -/
1
1
5
500
N/mm2
5
load
Stress
Vickers
hardness
HV
’
i
/
l
1
I
i1
,
05
class
properties
Propefty
Tahle 5 - Mechanical
/
I
j
1
Ir
1
I
I
!
I
Q-l-2)
j
I
Nut
-
N/mm2
Stress
under
proof
Load
i
T
8
j
1
I
l-lj
1
I
l
/
N/mm2
%
Stress
under
proof
Load
117
-
,min.
1
I
1
j
1
1
t
f
max.
NQT:j
state
state
Nut
j
Nut
I
1
I
1
I
i
180 1 302 1 NQTU
min.
Vickers
hardness
i-iV
302
max.
Vickers
hardness
HV
4
i
2
styl e
1
-
style
2)
1)
i
IM39
M16
j
’
!
920
950
188
170
min.
HV
QT = Quenched and tempered.
9
302
max.
Vi ckers
hardness
NQT = Not quenched or tempered.
Ml6
M-l0
Thread
1l Stress
f under
1
1
i
l
*-
’
NQTI j
state
Nut
2
style
1
353
GT?)
1
style
Nlmm2
1 060
1 050
1 040
1
272
Ai
I
Ii
I
I
-
1 170
1 140
1 140
i
l
1
040
i
I
1
i
1
i
min. max. ’ state
Nut
Stress
under
proof
load
-&
class
1 140
1
Vickers
hardness
I-W
?i
j
Property
1 040
N/mm2
SF
Stress
under
proof
Load
T
10
-
i 2%
i
1
c
state
1
i
I
1-1
l
1
I
!
1
-
/
l
Nut
I I
l1 353 11 cy-21
1 I
min. ’1 max. ’
l
I
Vickers
hardness
HV
-
1
style
i
f
I
I-
!
c
1
l-
t
i
I
1 200
1 190
1 160
1 150
1 150
N/mm2
%
Stress
under
proof
Load
T
12
i
i min.
I
t
/
1
I
4
272
/
:
I
4
l
<
353
max.
Vickers
hardness
HV
,1
/
/
T
~
QT2)
state
1
1--l
i
3
I
j
/l
style ’
I
7-
Nut
3) The maximum bolt hardness of property classes 5.6 and 5.8 will be changed to be 220 HV it: the next revision of ISO 838-1: 1988. This is the maximum bolt hardness in the thread engagement area
I whereas only the thread end or the head may have a maxlmum hardness of 250 HV. Therefore the values of stress under proof load are based on a maximum holt hardness of 220 HV.
I
NOTE - Minimum hardness is mandatory only for heat-treated nuts and nuts too iarge to be proof-!oad tested. For all other nuts, minimum hardness is not mandatory but is provided for guidance only.
For nuts which are not hardened and tempered, and which satisfy the proof-load test, minimum t ardness shall not Se Cause for rejection.
/
l
l
!
2
2
j
/
i
/
i
!
it
l
!
1
j
I
M5
M6
M7
M8
NI10
IA12
M14
M16
Ul18
M39
I
4
4
M36
3,5
3
3
2,5
375
I
j
i
i
l
'
2,5
2,5
IJ5
195
1
0,8
02
M33
M30
M27
IW24
M22
i
1,25
;j
0
rd4
M20
1
i
M3,5
061
0!5
l
i
M3
l
I
1
j
i
!
1
I
f
I
976
817
694
561
459
353
303
245
192
757
115
84,3
58
36,6
28:9
20,l
?4:2
0,75
6J8
$33
mm*
/
I
/
1 Thread
pitch
1
mm
I Nominai
of the stress
mandreiarea
]
4
;* S
I
it
i/
Thread
l
j
2530
1910
04
1
370900
310500
43700
32 000
18300
29 000
/ 488 000
I
1i 308 500
1 d2 200
I
I
i 57500
/
i
22 000
13 900
/
10000
7 100
3400
2500
05
1 14500
/
Il
/
7640
5400
l
l
1
/
!
1
1 11 000
/
I
I
j334oi44ooj
l
1
ll
lI
1
11
Yable
4
j
-
-
-
1 497 800
f
70 200
51400
34200
21 600
1 614 900
/ 514 i700
j
i
;
1 ?6800
1
-
-
1
11 700
8 250
4550
3550
2600
style
5
,
11
/
i
/
j
i!
j
i
l
6
13500
9 500
80 500
59000
39400
/ 702 700
/ 588 200
l
/
/
i
1 24 900
897 900
751 600
638 500
516 100
422 300
324 800
278 800
225 400
176 600
138 200
SO1 200
74 200
50500
31 800
24700
17 200
:2 740
7000
5400
5 250
4 000
3 000
style 1
4050
1 19300
j
i
I
l
i
i
j
1
IN
-
-
-
-
-
-
-
-
-
-
-
style 2
868 600
727 100
/ 617 700
1
1 499300
408 500
314 200
1 269 700
218 100
1 170 300
1
!
/
!
l
1
'
i
Proof ioad (A, x Sp)
8
cfass
thread
, Property
- Coarse
1 style
I
:
Load values
-
-
-
-
-
/ 416 700
f
l
1
/
/
1
1
1
;
1
Proof
1’ style
I
1j!
6-
7 900
6 100
897 900
751 600
638 500
516100
422 300
324 800
l 278 800
t 225400
1 +l76 600
1
149 200
I/ ao 100
I
i 109 300
54 500
34400
26400
ia 400
I
1 i3000
]
I
f siyle 2
1
1
’ 4 500
9
'
,
/
1
'
1
1
'
/
;
j
j
I
]
/
1
1 035 000
866 000
735600
594700
486500
374 200
321 200
259700
203500
164 900
120800
88 500
60 300
38 100
30 100
20 900
14 ao0
9 150
7050
5 200
style
Kl
10 000
7 700
5700
1
41 700
?34 600
g8 6oo
I
j
,
1
1
i
1
I
-
-
-
-
-
-
-
-
-
j 183700
j/
t
1 66100
/
! 16 200
l
! 22900
1
1 32900
!
i
l
1
I
i
1
j style
I
I
1
II
2
980 400
832 800
673 200
550 800
423 600
363 600
294 000
230 400
186 ao0
136 900
100 300
67 300
42 500
IO 100
7 ao0
5 800
style
1 171 000
12
l
i
ISO 898-2: 1992(E)
7 Failure loads for nuts with nominal
height > 0,50 but < 0,8D
shall be the last
minimum
material
quarterside.
of the
Gg range
on the
The vaiues of failure loads given in table 7 for guidante apply to different bolt classes. Bott stripping
is
the expected
failure mode for lower strenqth
bolts,
while
nut stripping
tan be expected
for’ bolts of
higher property classes.
Table
7-
Minimum
-Proof load
stress of the
nut
Property
class of
the nut
04
~-----05
8
8.1
bolt stress
occurs
when
stripping
Miniitrum stress in the core of
holt when stripping occurs
PJ/mm*
dh= d DU”
N /mm*
380
_ -~--500
Test methods
Proof
load test
"1 Dll
The proof load test shall be used wherever
the capacity of available
testing equipment
permits,
and
shall be the referee method for sizes > M5.
Figure
The nut shall be assembled
on a hardened
and
threaded
tesl mandrel
as shown in figures 1 and 2.
For referee purposes,
the axial tensile test is decisive.
The proof load shall be applied against the nut in an
axial direction,
and shall be held for 15 s. The nut
shall resist the load without failure by stripping
or
rupture, and shall be removable
by the fingers after
the load is released.
lf the thread of the mandrel
is
damaged
during the test, the test should
be discarded.
(lt may be necessary
to use a manual
wrench to Start the nut in motion. Such wrenching
is
permissible
provided that it is restricted
to one half
turn and that the nut is then removable
by the fingers.)
The hardness
minimum-
of the test
mandrel
shall
1 -
Axial
tensile
test
Load
t
Har
35
n
-c
_..._
i-----
be 45 tiRC
Mandrels
used shall be threaded
to tolerante
class
5h6g except that the tolerante
of the major diameter
8
is takon from tSO~2.
Figure 2 - Axial compressive
test
ISO 898-2:1992(E)
8.2
Hardness
The RockweIt
hardness
test shall
accordance
with the requirernents
test
For t-outine inspection,
hardness
tests shall be carried out on one bearing surface of the nut and the
hardness
shall be taken as the mean of three values
spaced 121Y apart. In case of dispute, the hardness
tests shali be carried out on a longitudinal
section
through the nut axis and with impressions
placed as
close as possible
to the nominal
major diameter
of
the nut thread.
The Vickers
hardness
test is the referee test, and
where practicabte
a Load of HV 30 shall be applied.
if Brineil and Rockweil
the conversion
tables
shall be used.
The Vickers
accordance
hardness
tests at-e appiied,
in accordance
with ISO 4964
hardness
test shall
wi1.h the requirements
The Brinell hardness
test shall
cot-dance with the rcquit-ements
be Garried out
of ISO 6507-1.
in
be carried out in acof ISO 6506.
8.3
Surface
integrity
For the surface
9
9.1
test
integrity
test, see ISO 6157-2.
Marking
Symbols
Marking
9.2
be carried out in
of ISO 6508.
sytnbols
are shown
in tables
ldentification
Hexagon
nuts of threads
> M5 and all property
classes
shall be marked
in accordance
with the
designation
System described
in clause 3, by indenting
on the side or bearing
surface,
or by
embossing
on the chamfer.
See figures
3 and 4.
Embossed
marks
shall not protrude
beyond
the
bearing surface of the nut.
Marking dot my
by mmufai;tr~rer’s
Figure 3 -
Exampies of marking with designation
Symbol
8 and 9.
Figure 4 -
he replaced
mark here
Examples of marking with code Symbol
(clock-face
System)
/
I
dot cannot
or Code symbol
jciock-face
System j
“) The marking
2
83
.-c
e
2
z
.I
be replaced
4
4
Table
8-
symbols
Tabie
9-
6
6
class
properQ
property
for nuts with
mark.
Marking
Propefty
/
L
1
l
ji
jI
t8
1
1
T
for nuts with
iWarking
by the manuiacturer’s
L
i
!
1
/
1
l
l
i
Marking
T
I
I
$
classes
8
8
classes
in accordance
9
9
in accordance
3.2
3.1
with
with
10
IO
i
i
/
1
1
t
l
:l
1
l
12
12”)
ISO 898-2:1992(E)
9.3
Marking
of left-hand
Nuts with ieft-hand
in figure 5 on one
denting.
thread
thread shall be marked as shown
beat-ing surface of the nut by in-
1) s - width across fjats.
Figure
9.4
Figure
5 -
Left-band
thread
is reguired
for nuts with threads
The alternslive
marking
for Iefl-hand
in figure6 may also he used.
> MS.
thread
Alternative
Alternative
left-hand
thread
marking
marking
Alternative
or optional
permittcd
marking
as stated
in 9.1 to 9.3 is left to the choice of the manufacturer.
marking
9.5
Marking
6 -
shown
Trade
(identification)
marking
The trade (identification)
marking
of the manufacturer is mandatory
on all products
covered
by the
marking
requirements
for
property
obligatory
classes,
provided
this is possible
for technical
reahowever,
shall be marked
in all
sons. Packages,
cases.
11
ISO 898-2:1992(E)
Annex A
(informative)
Loadabiiity
(Explanatory
of boltkd
note concerning
the specifications
of Technical
reaardina
nut strength and nut design-)
%J
In the case of bolts
cates:
minirnum
tcnsile
stress ratio.
and screws,
strengt.h
the symbol
and yield
indi-
to ultimate
EXAMPLE
Property
class
8.8
First figure
(“8” in 8.8) = l/lOO of the
mininium
tensile strength,
in newtons per
Square millimetre.
Second figure (If8” in 8.8) = ‘IO times
yield stress ratio (0,8).
the
Multiplication
of
these
two
figures
(8 x 8 = 64), == l/lO of the minimurn
yield
stress, in newtons per Square millimetre.
b) In the case of nuts:
designation
number
tensile
strength,
in
melre, of a bolt and
with the nut, tan be
yield stress.
= l/lOO of the minimum
newtons
per Square
miiiiscrew, which, when rnated
loaded up to the minimum
EXAMPLE
Roll or screw
8.8 -
nut 8
connection
loadablc
up to
stress of the holt or screw.
12
Committee
ISO/TC
2
J
Following
the introduction
of the ISO Recommendation
on property
classes
for bolts and screws
(lSO/R 898~1:1968),
an ISO Recommendation
on
property
classes
for nuts (ISO/R 898-2) was published
in 1969. These
ISO Recommendations
together
produced
a new System for the property
classes
of bolts, screws and nuts, and, in conjunction with new rnarking
requit-ements,
provided
a
clear Statement
of the loadability
of a bolt-nut assetnbly.
a)
connections
minimum
yield
Following
publication
dations,
this System
introduced
worldwide
cess.
of both
ISO Recommenof property
classes
has been
and has proved to be a suc-
In 1973 the Sub-Comtnittee
SC 1 of lSO/TC 2 commenced
revision
of the BO Recommendations
on
the basis of experience
gathered
and also planned
to convert
both Recommendations
into ISO Standards.
In 1974, a draft lSO/DlS 898-1 on property
classes for bolts and screws was pubiished,
incorporating
certain
modifications
and Supplements.
which, however,
did not Change the System of the
property
classes
in principle.
This draf? was then
revised once more. A second draft was prepared
in
1977 and has since been adopted by a Iarge majority
of the member
bodies of ISO. While considerable
effort was required
to develop thoroughly
this draft
concerning
property
classes for bolts and screws, it
was finally resolved
to %Z
;
s;aZisiaction of the interested
countries
within
Sub-Committee
SC 1 of
iSO/TC 2 and now is aqreed to by ISO. More extenthe substance
of the
sive by far, and touching
specifications,
was the work on a revised Version of
the ISO Recommendation
ISO/R 898-2 and its conversion into an ISO Standard on property classes for
nuts.
Experience
had shown that, while the concept
of
property
classes in conjunction
with a norninaI 0,81.)
nut height
is simple
and straightforward,
certain
practical
difficuities
arise. First, it is sometimes
difficult or impossible
to achieve specified
nut properlies
with
the
most
econornical
materials
and
methods,
for example
with fine threads and certain
sizes of coarse threads.
Secondly,
compliance
with
the requirernents
does not necessarily
provide the
assurance
that the assembly
would resist thread
stripping
during tightening.
Previously
it was considered adequate
if the nut proof load was designed
equal to the holt minimum
ultirnate
strength,
however, the advent of yield Point tightening
methods
and improved
understanding
of the interaction
between nut and bolt threads showed the nuts required
re-design
to provide greater resistance
to stripping
of both the internai and extemal
threads.
ISO 8984:1992(E)
For exampie,
consider
that Ihe effective
tensile
strength
of a holt of class 8.8 rnay be belween
800 N/mm2 and about 965 N/mrn’ (determined
froni
the maximum
hardness)
in sizes up to M16. Consequently
the yicld
stress
may
range
between
640 N / m m * and 772 N/mnI* for a vield to ultimate
stress
ratio of 80 9/0. With the uie of yield point
tighteninq
it will be Seen that the tightening
stress
approaches
Zhe proof stress. Recent research
has,
in addition,
shown tlIat a nut tested with a hardened
mandreI is capable of susfaining
a higher ioad before strippitIg
than when tested with a boit of the
appropriate
property ctass. For exampie,
a property
class 8 nut when tesled with a mandrel
of 45 HRC
will be capable of approxirnately
IO o/o higher load
than when lested with a properiy
ctass 8.8 bolt of
dimensions
simitar 10 the mandrel.
Therefore.
a nut
that just meets a proof stress of 800 N/mn? with a
hardened
mandret might only be expected t.o sustain
a load of approxirnately
720 N/mm* when mated with
a property
class 8.8 holt of minimum
dimensions.
lt
will be Seen that stt- ippi ng of fl1e t h read S may occu t
when t ightening
fr0 st ress es in excess 0 f ttIis, and
frorn the boit rnechanicai
pro pert ies it will be seen
that this could he a frequent
acc u t-ren ce with yieid
point tightening.
lt might be aryued,
however,
thal:
under torque tension toading the tensile strengtlI
of
the holt is reduced by about 15 %G, bu1 it shoutd also
be realized
that the stripping . strenylhI
of the assembly is also reduced by almost the Same amount
under tot-q ue te nsion loading.
In addition to t.he infroduc tian
of yield
tighfening
mettIods,
Point
changes
in certain ISO Standards
were under consideration
that would
also adversely
affect ttiis
stripping
tendency.
Upgrading
of bolt and screw
mechanical
properlies
was pt-oposed
as shown in
iabie A.? (which is an excerpt
from ISO 898-l), the
pur-pose of which was to utilize futly the availabte
strength of the commonly
used materiats
for grades
4.8, 5.8, 8.8 (above M16), 10.9 and 12.9.
Another
proposed
Change u nder consideration
at
this tin ‘Ie wa s 1.0 reduce ttIe wid ttI across fl ats of
certain stzes of h exagon prod ucts to provide economies through
optimized
materiat
use. As a resutt
of these and other factors, certain mernber countries
(Canada, Germany,
NettIertands,
Sweden, UK, USA)
of Sub-Cornmittee
SC 1 of tSO/TC 2 conducted
research and extensive
testing of nut-bott assen-ibties.
Tests
inciuded
a fuit va riety of prod uct sizes,
streng fl7 ieveis and nIate riais. in qeneral,
test s were
x
conducted
on typical production
fasteners
utiiizing
Standard
matet-ials.
Test Parts were
accurately
measured
for dimensions
and material
stt-ength
which then aiiowed appropriate
statisticai
inferpretation of the data. Results of the various invesfigaiors
were evaluated
by Canada a n d fo u n d to corre t ate
Welt. A yeneral
series
of for m jtae res\ rttcd t.hat
\
could be apptied to predict the assembly
strength
of threaded
components
with ihe ISO 68 basic
thread
p rofi t e. These
fi nd i n qL s were
discussed
within Sub-Committee
the various national committees.
SC I as wetl
as in
Despite
the initial retuctance
of the committee
to
permit changes
in existing
specifications,
the test
prograrnme
clearly
indicated
that there was inadequate
resistance
to assembly
stripping,
brought
about Iargely by the improved
tightening
methods
and upgrading
of mechanicat
properties.
The problem was both one of boit thread stripping
and nut
thread stripping,
and, as a result, it was conciuded
ttIat the mosf viable means of overcoming
the problern was by increasing
.the nominal 0,811 nut height
where required.
It is not the purpose of this annex
.to provide
a detailed
description
of the tests conducted and the nut design method
devetoped,
for
which the reader is referred to the foilowing
pubiication which provides a summary
of resuits and the
nIcltIod employed:
“Armlysis
and Design of Threaded
Assemblies”,
E.M. Atexander,
1977 SAE Transactions, Paper No. 770420.
The caicuiation
for nuts of proper-ty ciasses 4 to 6
according
to ttIe Alexander
theory was not based on
tiIe maximum
bolt hardness
250 HV, as given in
ISO 898-1, see tabie A.l, because this is a tlardness
which may occur at the boit end or ttIe head oniy.
Therefore
it was agreed to make caicuiations
on the
basis of the effective
maximunI
hardnesses
within
the thread engagement
part of the holt, which are
\qiven in table A.2.
Simiiar
graduated
hardness
in ISO/R 898-1:1968.
vaiues
were
specified
The above work showed
that many factors
influenced resistance
of the stripping
of threads,
inciuding folerances,
pitch, beit mouthing
of nut minor
dianIeter,
size of countersink
in nut, relative strengfh
of nut threads to bolt threads, tength of engagemenf,
width across
fiats of nut, and styie (for exampte
hexagon
flange),
coefficient
of friction,
number
of
ttIreads in the grip, etc. Analysis of the various sizes
of fasteners
on this basis indicated
.that it was not
appropriate
to have a fixed nominal
nut height, for
exampte
0,811 as before, but rather each Standard
assembiy
shouid be designed
to give a suitable
resistance
to stripping.
The resuit of this anaiysis
gives the nut heights shown in table A-3.
It will be Seen that .there are two stytes of nut,
approximateiy
10 % highetthan
styie 2 being
styie 1. Styie 1 height
is intended
for property
ciasses 4, 5, 6, 8, 10 and 12 (up to M16) in conjunction with appropriate
mechanical
propel-ties,
while
style 2 dimensions
are intended
for use with property ciasses 8, 9 and 12, also with appropriate
meThe higher
style of nut was
chanicat
properties.
primarily
developed
as an economical
cold-formed
nut to be used with property
class 9.8 boits and
screws and it also provides
suitabte dimensions
for
a heat-treatabte
nut of good ductility
for use with
property
class 12.9 botts and screws. The intended
13
ISO 898-2:1992(E)
applications
of the two styles of nuts at-e detaiied in
table 5, ft-om which it is seen that this additional
style
of nut does not mean that dual stocking of pst-t geometry will result.
The values of table 5 are only related to nuts with
coarse thread.
The Same applies
also to the test
loads given in table 1. For t-Us with fine pitch tht-ead,
see ISO 898-6.
An overlapping
between style 1 and style 2 occurs
only in two cases. In the case of style 1, property
not
of nuts,
class 8 allows
the
employment
quenched
and tempered
(cold-worked
low-carbon
steel) only up to and including
M?6; above M16 the
nut style 1 has to be quenched
and tempered.
However, it is possible
in this case to use alternatively
the thicker.
not quenched
and tempered,
style 2.
This is a question of economics
in the final analysis.
In the case of property class 12, it is not appropriate
to use style 1 nuts above size M16. Due to the required proof foads, it would be necessary
to raise
the hardness
of the nut to such an extent that its
ductility,
which
is necessary
from the functional
Point of view, would be impaired.
Hence, the thicker
style 2 nuts quenched
and tempered
are necessary
in this case. If necessary,
it would be possible
to
restritt
the use of these nuts to sizes above M16, so
that
then
no overlapping
between
style 1 and
style 2 would occur in the case of property class 12.
The loads given in table 1 at-e based on a test
mandrel
as specified
in this part of ISO 898 with a
minimum
hardness
of 45 HRC and thread tolerante
of 5h6g (major diameter
of 6g in the last quarter).
ISO 898-1 and this part of ISO 898 on mechanical
properties,
ISO 4014 to ISO 4018 on hexagon
bolts
and screws, and ISO 4032 to ISO 4036 on hexagonal
nuts have been published
reflecting
the revised
mechanical
properties,
changes
in nut heights and
changes
in width across flats (width across flats of
MIO, M12, M14 and M22 revised to 16 mm, 18 r-nm,
21 t-nm and
34 mm
respectively
fror-n 17 mm,
19 mm, 22 mm and 32 mm) as recommended
by
ISO/TC 2.
This part of ISO 898 makes the following
Statement
concerning
the property
classes
for nuts with full
loadability:
A bolt or screw of a particuiatpropet-ty class assernbled
with the equivalent
pt-operty
class of
nut, in accordance
with table 2, is intended
to
provide an assembly
capable of being tiqhtened
to achieve
a bolt tension
equivalent
to ihe bolt
proof Load or yield load without
stripping.
Additionally,
geometry
and mechanical
proper-ties
of nuts up to M39 and property
class 12 of 6H
thread tolerantes
are designed
to pt-ovide fot- a
high deqree of t-c-tskpl,~nee lo sirlpping
(at least
IO % b&t breakage
of individual
lots even under
adverse
minimum
material
conditions)
when inadvertently
overtorqued,
in ot-der to warn the
user- that the installation
practice
is not appropriate.
Once nut dimensions
were determined
based on
assembly
strength
criteria, the proof loads of these
nuts with a restricted
size hardened
rnandrel were
determined.
The t-esult was that Stresses
under
proof load were not constant for each property class
of nut brit varied
with size. Accordingly,
table 5
Shows revised Stresses under proof load and hardness values for nuts. The property
classes 04 and
05 (previousiy
06) for hexagon lhin nuts with resultare also indicated
in this taant reduced loadability
ble. These nuts incidentally
were not designed
to
provide resistance
to stripping and are simply based
on a fixed height of 0,61).
Phe stresses
under proof load given in table 5 are fot
the Standard tolerante
of 6H usually applied to nuts
for mechanical
fasteners.
Where a Iarger tolerante
or allowance
is applied,
these Stresses
should be
modified
by a factor as shown in table 1.
Table
3.6
Property
Tensile
Tensile
strength,
class
num.
A,
Pl /m r-r-+
---.------min.
4.6
300
400
330
400
_--------_-__----.---____-------_- ------ ---- --- -, --- --- _-_--, -_-__~_
Vickers
ness
L
34
hard-
max.
A.1 -
Property
classes
4.8
5.6
5.8
_--___-_--.---__.
400
--------------~259
tIV250
tiv
II ---
.-.-----------,-.----w-e
.--
, 250 t IV
I 250 t iV
Certain users of the referenced
Standards could not!
of necessity,
participate
in their detailed
development and it is hoped that this explanatory
note will
provide
increased
understanding
of this reIatively
complicated
subject.
490
400
590
- ------.---_-~-_.-------~
-.---__--__~
420
500
500
and screws
600
500
0.8
8.8
6.8
< M16
> M16
800
800
900
-_____I_____
520
520
.-__ __._~__
____.____._-_
.---__._-__
- ___.____._-_ -l 250 t-w
t-iV l 259 I-iV
for bolts
250 tiv
HV
------.---_-~ --.__.____
-___-~~
__-__-_
800
830
900
900
600
-.--.------.--.------, ._-----.-----..---------_-_----- ----+- --__
-~-250 t-iV l 320 tiv
tiV
l 335 t-w
t-W
10.9
1 000
------_-___
1 200
.--_--.<
_
1 040
1 220
220
-..
-..---_---_-I_- ------_--____- -.-.
I 360 tiv
t iV I 380 t-W
---.
12.9
435 t-iV
HV
ISO 898-2:1992(E)
Table A.2 - Effective
maximum
hardness within
engagement
part of the bolt
thread
Praperty
class
Maximum
3.6
158 HV
180 I-IV
5.6; 5.8
220 HV
6.8
250 HV
A.3 -
Heights
1
hardness
4.6; 4.8
Table
the
nuts
of hexagon
Nut height
_______-_
Width
Thread
across
w---_--_I_e_------
flats
---
Styie
___-..--
__~_
max.
mm
mm
mm
mm
mm
8
44
498
51
10
-. ---- _----~~.-
4.9
11
6,14
0,94
__-- --------~-~
477
-~-__-------
MIO
_.I __-.__-_--_--_~_.
___~__
30
8,94
9,30
0,93
.----.----
15,l
15,8
--_--_-.---__---
34
--.----~----I-36
46
____- -~-----------
_
---_--
20,2
21,5
_____ -y._------"l--p-
0,90
23,8
0,88
-0,85
---.,
25,6
24,3
-~27,4
._-. ---- -----
28,7
_-_~--
29,4
31,0
__-__--_-__------_-.-__- - _----_._----_----. ___
______
-___.-.-_---._.-.-.
-- _-___
60
19,0
0,8R
20,5
__~---_--_--_L-----.-.-~-
--
31,8
33,4
l,oo
14,l
-----..
20,3
--- - --
1,02
0,98
._-.
1,02
-----
21,8
0,93
23,9
-------------
l,oo
26,7
0,99
28,6
m---.---p
0,95
32,5
0,98
-- _~_____~
22,6
25,4
,,_-----..--------P
27,3
~-
1,Ol
16,4
--..-----.---P-u
16,9
17,6
-__--..-..-w-----v
19,4
___---
---~
55
0,90
P-----P-
12,00
13,4
--
15,7
_-_--__-
0,88
1,03
_--~-__.
I
18,l
22,5
41
50
l_-l~------_-r_
18,0
_-,-____
0,92
_.____----.
7,20
---
11,57
_
l4,8
16,9
M30
___- -.-------_--
M39
0,94
-.------
14,l
- -~ ---
.--_l_---
M36
7,50
.~------~---
0,91
M27
_- ___-_-__---.---~.---
M33
7,14
_I__
12,8
Ip--._---------
27
_-.___~------_
M24
0,85
0,90
12,l
a,.--
6,84
--
IO,80
__p--e..---
- ----- ---
0,95
5,7
0,93
---_-PP-
18
10,37
1,02
-
8,40
0,84
__._-__ __-._J------_ ,_I-_----------I_----.----
Ml6
24
_-____.___
--_ .-- ._--_---- .-- ___-___I----I_~---_
..__~-
594
16
8,04
__-_ -._---_-.-. ---- ._--"---------
21
M22
0,87
~_-~-I_-----_-
6,80
rn/ Zl
-----
---
_-~----
M20
6,50
___~
6,44
_~ __.______-_
- -...- --.-----
M18
572
-___-
13
M8
_~_I-.-_--.-.------.I
Ml4
----
min.
M7
_-___
^____
-------.- ---.
---
max.
_-~_-
M12
-----
styk? 2
min.
MS
M6
___._-_----~._-_-_~-_
---P--P
1
0,87
-------
30,9
0,136
__ .___-_ ------
33,l
--.--.-PI
34,7
---- ----.-
0,96
- _----~--
35,9
37,5
0,9G
-_.-
0,86
1
PP
15
ISO 898-2:1992(E)
Annex B
(informative)
Bibliography
Corrosion-resistan
-- Specifications.
[l--j
ISO 3506:1979,
steel fasteners
[2]
ISO 4014:1988, Hexagon
grades A and B.
head
t
bolts
s tainless
[5]
-
Hexaqon
..
head
bolts
ISO 4017:1988, Hexagon
uct grades A and B. ’
head
screws
-
Prod-
head screws - Prod-
[8]
ISO 4033:1979, Hexagon
grades A and B.
nuk,
style 2 -- Producf
[9]
ISO 40341986,
C.
nuts
-
Hexagorj
[ IÖJ ISO 4035:1986, Hexagon
thin
-- Product grades
A and B.
L
[ 1 l]
16
Hexagon
nuts, sfyle
Product
-
ISO 4018:1988,
uc t grade C.
ISO 40323986, Hexagon
grades A and 8.
-- Product
ISO 4015:1979, Hexagon head bolts ~ Product
grade 8 -- Reduced hanh (slw?k diameler
approximately
egual to pitch diameter-).
ISO 4016:1988,
grade C.
[S]
ISO 4036:1979, Hexagon
grade B (urhamfered}.
thin
I -- Product
Product
nuts
nuts
grade
(chamfered)
-
Product
This page intentionally
left blank
ISO 898-2:1992(E)
-----PP- .-__l-_<-_-----
. . .--.----
_--
--
.
-----.---
.--.I__-
-----I-M---
p-w--
.-----
----*-.-------.-
--
_.------
-
-___
_ ____l_-_l_l.
~
---._--_--.-
----
------------~
- ----.~-
-
-.--
----_-.--
UDC 621.882.3
Descriptm:
Fastwem,
twtc; (fastenws),
F)rice based on 16 pagcs
---~---.----~I_..--.~-----.-. ------------------
-- -_----_-~__
coarse
threads,
-.--__
- --__-,
___.__
--- -___
___-____
specifications,
mechanical
w-v_._~--------.__
______-____.__
properties,
_.__ :Le
tests,
designation,
rrvuking.
-----..---------~----=_ll__l--.---.-------- -------_I----..---
_--------
_.--