Width Across Flats; Hex-Head Bolt Strength Markings - Honda Motorcycle Service Manual

GENERAL INFORMATION
WIDTH ACROSS FLATS
The width across flats is the portion where tools such as a
wrench or a socket are applied. Applicable tool sizes are
represented by these widths. The denomination of a " 1 0 m m
wrench," for example, represents a wrench t o be used on hex-
heads with widths across flats of 1 0 mm.
On the right is a table t o show representative widths across
flats and thread sizes often used for Honda motorcycles. Not
all widths across the flats are shown.
Some other common widths across the flats are
22,
24, 27,
30. 3 2 mm, etc. Spark plugs have particular width across
flats; they should be removed with special spark plug wren-
ches (16, 1 8 and 20.6 mrn).
HEX-HEAD BOLT STRENGTH MARKINGS
Strength marks, indicating material type, are visible o n the
head of some hex-headed bolts. Bolts are classified into stan-
dard bolts and h~gh-tension bolts by material types. During
assembly, take care not to install any high-tension bolts in the
wrong place. Note that while standard bolts are tightened to a
standard torque unless otherwise specified, high-tension bolts
always have their o w n specified torque values. 6 m m SH bolts
without strength marks (small-headed flange bolts with a
width across flats of 8 m m and a thread size of 6 m m l are all
considered standard bolts.
DR-type (or dished-headed) bolts without strength markings
(flange bolts with hex-heads and weight reduction holes in
them) are classified by outer flange diameters. Be careful
about the installation points and the torques of high-tension
bolts having the same hexagon dimensions as standard bolts,
but having larger flanges.
Hexagon portion
M
Width
across flats
8
8
10
1 2
1 4
1 7
1 9
5
6
8
1 0
(Thread diamel
x (pitch)
5 x 0.8
S T R ~ N G T H
MARK
Mark
/
No mark
/
O
or
O
/
10
DISHED HEAD
I
12
Tension
strength
Class.
STANDARD HI-TENSION
BOLT BOLT
I
Strength
Class.
/
DR-TYPE
BOLT
50-70
kgimm2
Date o f Issue: Nov., 1 9 8 9
o
HONDA MOTOR CO., LTD.
1-7
5,8
80-100
kgimm2
100-120
kgimmZ
Standard Bolts
120-140
kgimm2
8.8
Hiah tension
10.9 12.9