ANSI Wood Screw Standards: B18.6.1

The American National Standards Institute (ANSI) is a private non-profit that oversees the development of standards for products and systems in the United States. They are a HUGE organization with thousands of standards founded in 1918. For our purposes, we're interested in the fastener standards which are very useful.

Imagine if there were no standard sizing for fasteners. The wood screw you bought from Company A might not fit the cup washers you had to get from Company B. But thanks to ANSI, a number 8 wood screw is the same size no matter where it comes from, and the taper on it's head is the same too. ANSI is basically saving us all from a world of aggravation.

There are books and books of ANSI standards and much could be written about their history and usefulness but what you came for was the wood screw standards. Use our handy diagram and table below:

 

ANSI STANDARD WOOD SCREWS

 

ANSI Flat Head Screw and Oval Head Wood Screws per. ANSI B18.6.1 
Nominal
Size
Threads
per
Inch
O
Tot.
Hgt.
of
Head
K
Height
of
Head
T
Depth
of
Slot
U
Depth
of
Slot
V
Depth
of
Slot
Max.
Min.
Max.
Min.
Max.
Min.
Max.
Min.
Max..
Min
0
32
.056
.041
.039
.031
.015
.010
.022
.014
.030
.025
1
28
.068
.052
.046
.038
.019
.012
.027
.018
.038
.031
2
26
.080
.063
.053
.045
.023
.015
.031
.022
.045
.037
3
24
.092
.073
.060
.051
.027
.017
.035
.027
.052
.043
4
22
.104
.084
.068
.058
.030
.020
.040
.030
.059
.049
5
20
.116
.095
.075
.065
.034
.022
.045
.034
.067
.055
6
18
.128
.105
.082
.072
.038
.024
.050
.037
.074
.060
7
16
.140
.116
.089
.079
.041
.027
.054
.041
.081
.066
8
15
.152
.126
.096
.085
.045
.029
.058
.045
.088
.072
9
14
.164
.137
.103
.092
.049
.032
.063
.049
.095
.078
10
13
.176
.148
.110
.099
.053
.034
.068
.053
.103
.084
12
11
.200
.169
.125
.112
.060
.039
.077
.061
.117
.096
14
10
.232
.197
.144
.130
.070
.046
.087
.070
.136
.112
16
9
.248
.212
.153
.139
.075
.049
.093
.074
.146
.120
18
8
.290
.249
.178
.162
.083
.054
.106
.085
.171
.141
20
8
.296
.254
.182
.166
.090
.059
.108
.087
.175
.144
24
7
.347
.300
.212
.195
.106
.070
.124
.100
.204
.168
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