normazione
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
1
GENERAL
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E T H E O N L Y
T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
3.6
Surface protective coatings
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
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N Some examples of quench–and–harden cracks are shown in Figure 1 for screws and in Figure 2for
nuts.
Figure 1
Circumferential
quench–and–
harden crack
adjacent
to the radius fillet
Quench–and–
harden crack
on the edge of
the head Crosswise
quench–and–
harden crack
Quench–and–har-
den crack
on thread bottom
Quench–and–har-
den crack
on the crest of the
incomplete thread
Quench–and–harden crack across the
top of the head, generally
extending along shank
or one of the head flats
Quench–and–har-
den crack
crosswise to the
bearing face
with collar
Lengthwise
quench–and–
harden crack
Quench–and–
harden crack
extending
radially
into the radius
fillet
Quench–and–harden
crack
at bottom of the flute
Quench-and-harden crack
Sect. A–A
(A)
(A)
Figure 2
Quench–and–har-
den crack
on the threads
Quench-and-harden crack
Quench-and-harden
crack
No quench–and–harden cracks of any size and in any location are allowed on the screw or nut.
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
Figure 3
Stamping cracks on top face of head
Figure 4
Inclusion cracks on bearing surfaces or on threading
Stamping cracks on bearing surfaces
In the case of screws, cracks may not have lengths greater than the screw nominal diameter d and width or depth greater than 0.2 to 0.01 d (in mm), when located on head top face. Instead, when they are located on the head swollen edges the cracks allowed may be less wide than 0.25 + 0.02 d (in mm) and depth less than edge height.
In the case of nuts, cracks are allowed when the nut passes the expansion test (see to
T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
3.1
4.2.2
Hex socket head screws Figure a)
Not allowed: joins the head outer surface and the socket.
Figures b) c)
Figure d)
Allowed
Irregularities that may intersect not allowed.
Allowed but
only if lengthwise.
Allowed
Allowed, but not in the area mating
with the wrench (socket bot-tom)
Not allowed
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E T H E O N L Y
Figure 5Figure 6
Flakes caused by stamping
Flakes caused by stamping
Flakes caused by stamping
Flakes caused by stamping
T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
Some examples of scoring are shown in Figure 7 for the screws and in Figure 8 for the nuts.
Figure 8
Figure 7
Line mark, normally straight or slightly curved,extending lengthwise.
Tool marks
Tool marks
Marks left by the tool as a result of
a deburring operation
Tool marks Scoring marks on the shank and head of the screws not exceeding the dimensions indicated in DIAMETER
SCORING SIZE
THREADING DIAMETER Max width (mm)
0.130.10 + 0.015 d 0.250.10 + 0.015 d
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
Figure 9
Figure 10
Pitting Pitting
Pittings on the screw head bearing area or on nut side face bearing area caused by lack of material filling are allowed if their depth does not exceed 0.25 mm and their total area does not exceed 5 %of the actual bearing face surface. Pittings on the other surfaces are allowed provided their depth does not exceed 0.25 mm, threading excepted.3.14.6
Dents and incisions
Figure 11Figure 12
Dents on threads are allowed provided it is possible to screw on the threaded ring or plug GO gage,by applying a maximum torque, expressed in N mm, equivalent to 0.01 F m d, for the screws and to 0.01 R d S r D for the nuts.where:
F m is the minimum UTS fromTables 6.d is the nominal diameter of the screw in mm.R d
is the unit inspection load indicated in Table 3.
T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
TABLE 3
STRENGTH CLASS
Figure 13
Folds allowed
on external radius fillet
Folds allowed
on external radius fillet
Folds allowed
on internal radius fillet
Folds allowed
on internal radius fillet
Fold allowed on the point
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
Figure 14
* H = Height of the fundamental triangle in maximum material condition
Folds
not allowed
Folds allowed
form irregularity allowed on the crest
Direction of pressure on the thread
Outside diameter Pitch diameter Minor diameter Outside diameter Pitch diameter Minor diameter Outside diameter Pitch diameter Minor diameter
Figure 15
Fold on
bearing face plane
Fold on one
face of the hexagon
Fold on the edge of flanged nuts
Folds
No folds of any length and depth are allowed on screw threads when:–they start at thread root;
–they start on thread flank and are turned towards minor diameter and extending under the pitch diameter;
–
they start on thread flank below pitch diameter and turned towards the outside diameter on the flank under pressure.
T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
On the screw threads folds are allowed when:–they start on the crest or flank, towards the pitch diameter;
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
Figure 17
Figure 18
TEST PROGRAMS Screws TABLE 4
TEST PROGRAM
TEST (A)
B
CHARACTERI-STRENGTH CLASS
STIC
PROCEDURE
R40 RCT R50 RCT
5.8
8.810.912.9
4.814H
R40 RCT R50 RCT
R40 IND R50 IND R80 IND
R50SD STAB
5.8
8.810.912.9R80SD
Tensile test on specimen §5.1.1F F F
tensile stress
Tensile §
T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
(continued
.
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
Figure 19
T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E
T H E O N L Y V A L I D R E F E R E N C E I S T H E O R I G I N A L I T A L I A N E D I T I O N
d is th
e nominal thread diameter
d o is th
e specimen diameter (tol. j Figure 20
according to UNI ISO 273, medium
series
d h Load
For studs, the head shall consist of a nut or similar suitable item screwed down to the bottom of the finer pitch threaded shank. Should stud threading be the same at either end, the head substituting item shall be screwed down to the bottom of the threading at root end (see Std.
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T H I S D O C U M E N T M U S T N O T B E R E P R O D U C E D O R C I R C U L A T E D T O T H I R D P A R T I E S
W I T H O U T P R I O R W R I T T E N C O N S E N T B Y F I A T A U T O S .P .A . I N C A S E O F D I S P U T E