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                                                 Nuts and Bolts


Often times we find ourselves in the hardware store searching for a new bolt to match an old rusted one,
the one we broke, or just because we want a new shiny one.  The following charts can be used to help
find what you need.

Tips for Hex Bolts:

  •  Bolt length measurements are made without the head.
  •  Grade 5 Standard (SAE & USS) and Metric 10.9 bolts are the best choices for automotive
       applications.  The Grade 8 bolt is a high strength bolt but harder, and more likely to snap in
       the wrong application.
  •  A Grade 5 bolt will have 3 radial lines on the bolt head.
  •  A Grade 5 hex nut will have 3 dots on it's face edge.
  •  Stainless steel bolts have the same approximate strength as the Grade 5 bolt.  They shouldn't
       rust and are also used in marine applications.  The markings vary.
  •  Metric 10.9 bolts have the same strength as the Grade 8 bolt.  Ford used the 10.9 bolt
       throughout the Mustang.
  •  The 10.9 Metric bolt is approximately 30% stronger than the Grade 5 bolt, and the 10.9
       lettering will be stamped on the head of the bolt.
Metric to US Conversions
Bolt Size Lengths
Metric
Millimeters
US
Inches
 
Metric
Millimeters
US
Inches
 
Metric
Millimeters
US
Inches
2
3/32
25
1
90
3-9/16
2.5
3/32
30
1-3/16
95
3-3/4
3
1/8
35
1-3/8
100
3-15/16
4
5/32
40
1-9/16
110
4-5/16
5
3/16
45
1-3/4
120
4-3/4
6
1/4
50
2
130
5-1/8
8
5/16
55
2-3/16
140
5-1/2
10
13/32
60
2-3/8
150
5-7/8
12
15/32
65
2-9/16
160
6-3/8
14
9/16
70
2-3/4
170
6-11/16
16
5/8
75
2-15/16
180
7-1/16
18
23/32
80
3-1/8
190
7-1/2
20
25/32
85
3-3/8
200
7-29/32
US Tap and Drill Bit Size
Tap
Drill Bit
 
Tap
Drill Bit
0-80
3/64
5/16-24
-
1-64
-
3/8-16
5/16
2-56
-
3/8-24
21/64
3-48
-
7/16-14
23/64
4-40
3/32
7/16-20
25/64
5-40
-
1/2-13
27/64
6-32
7/64
1/2-20
29/64
8-32
-
9/16-12
31/64
10-24
5/32
9/16-18
33/64
10-32
5/32
5/8-11
17/32
12-24
11/64
5/8-18
37/64
1/4-20
13/64
3/4-10
21/32
1/4-28
7/32
3/4-16
11/16
5/16-18
17/64
 
 
Fraction to Decimal Conversion (in inches)
Fraction
Decimal
 
Fraction
Decimal
1/64
.0156
1/2
.5
1/32
.0312
9/16
.5625
1/16
.0625
5/8
.625
1/8
.125
11/16
.6875
3/16
.1875
3/4
.75
1/4
.25
13/16
.8125
5/16
.3125
7/8
.875
3/8
.375
15/16
.9375
7/16
.4375
31/32
.968
Standard
Measured in inches
Metric
Measured in millimeters
Key
L
L
Bolt length
D
D
Diameter
T   (Per inch)
T   (Distance between
threads)
Thread Pitch
G
 
Grade Mark
 
P
Property Class