285
Drilling Guide
Metric Conversions
This catalog shows both imperial and metric measurements. In 
most cases, the metric dimension shown is calculated from the imperial 
measurement and rounded to a whole number. For example,  5/16" is 
generally shown as 8 mm, while an exact conversion would 
be 7.9375 mm. When referring to a line diameter, it is sufficient to 
approximate the conversion. In cases where a dimension is critical, 
exact metric dimensions are shown. For example, a clevis pin for 
a furling unit with a diameter of 1/2" is shown as 12.7 mm.
Fastener Types
HH, RH, TH, 
CH and SH 
measured from 
below 
fastener head 
FH measured 
full height
Hex head bolt
(HH)
Flat head
(FH)
Round head
(RH)
Truss head
(TH)
Cheese head
(CH)
Socket head
cap screw
(SH)
Length
Area
When you know
Multiply by
To fi nd
When you know
Multiply by
To fi nd
Inches
25.40
Millimeters
Square inches
645.2
Square millimeters
Inches
2.540
Centimeters
Square inches
6.452
Square centimeters
Feet
304.80
Millimeters
Square feet
929.0
Square centimeters
Feet
30.48
Centimeters
Square feet
0.0929
Square meters
Feet
0.3048
Meters
Square yards
0.8361
Square meters
When you know
Divide by
To fi nd
When you know
Divide by
To fi nd
Millimeters
25.40
Inches
Square millimeters
645.2
Square inches
Centimeters
2.540
Inches
Square centimeters
6.452
Square inches
Millimeters
304.8
Feet
Square centimeters
929.0
Square feet
Centimeters
30.48
Feet
Square meters
0.0929
Square feet
Meters
0.3048
Feet
Square meters
0.8361
Square yards
Weight
When you know
Multiply by
To fi nd
When you know
Divide by
To fi nd
Ounces
28.35
Grams
Grams
28.35
Ounces
Pounds
0.4535
Kilograms
Kilograms
0.4535
Pounds
Liquid
When you know
Multiply by
To fi nd
When you know
Multiply by
To fi nd
Liters
0.26417
Gallons
Gallons
3.7854
Liters
Liters
2.1134
Pints
Pints
.4731
Liters
Fastener
Drill for
clearance hole
Drill for
tapping
Fastener
Drill for
clearance hole
Drill for
tapping
mm
mm
mm
in
2
2.25
1.6
6-32
9/64
#36
2.5
2.75
2.05
8-32
11/64
#29
3
3.25
2.5
10-24
13/64
#25
4
4.25
3.25
10-32
13/64
#21
5
5.25
4.25
1/4-20
17/64
#7
6
6.25
5
5/16-18
21/64
#F
8
8.25
6.75
3/8-16
25/64
5/16"
10
10.25
8.5
7/16-14
29/64
#T
12
12.25
10.25
1/2-13
33/64
27/64"
16
16.26
14
5/8-11
41/64
17/32"
Pan Head
(PH)
To use the online calculator for finding length, area and weight go to www.harken.com
Fraction
Decimal
mm
1/32
0.0313
.7938
1/16
0.0625
1.5875
3/32
0.0938
2.3813
1/8
 0.125  
3.175
5/32
0.1563
3.9688
3/16
0.1875
4.7625
7/32
0.2188
5.5563
1/4
0.25
6.35
9/32
0.2813
7.1438
5/16
0.3125
7.9375
11/32
0.3438
8.7313
3/8
0.375
9.525
13/32
0.4063
10.3188
7/16
0.4375
11.1125
15/32
0.4688
11.9063
1/2
0.5
12.7
17/32
0.5313
13.4938
9/16
0.5625
14.2875
19/32
0.5938
15.0813
5/8
0.625
15.875
21/32
0.6563
16.6688
11/16
0.6875
17.4625
23/32
0.7188
18.2563
3/4
0.75
19.05
25/32
0.7813
19.8438
13/16
0.8125
20.6375
27/32
0.8438
21.4313
7/8
0.875
22.225
29/32
0.9063
23.0188
15/16
0.9375
23.8125
31/32
0.9688
24.6063
Equivalency Table

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