FLAT SOCKET SCREW

BASIC SCREW
DIAMETER
DIAMETER
A
H
FLUSH
TOLERANCE
M
T
J
Y
BODY
HEAD
DIAMETER
HEAD
HEIGHT
SPLINE
SIZE
6 LOBE
SIZE
SOCKET
SIZE
KEY
ENGAGE
DIAMETER
max
min
min
ref
ref
nom
ref
nom
min
0
0.0600
0.0600
0.0568
0.117
0.044
0.006
0.048
---
0.035
0.025
1
0.0730
0.0730
0.0695
0.143
0.054
0.007
0.060
---
0.050
0.031
2
0.0860
0.0860
0.0822
0.168
0.064
0.008
0.060
---
0.050
0.038
3
0.0990
0.0990
0.0949
0.193
0.073
0.010
0.072
---
1/16
0.044
4
0.1120
0.1120
0.1075
0.218
0.083
0.011
0.072
TX-9
1/16
0.055
5
0.1250
0.1250
0.1202
0.240
0.090
0.012
0.096
TX-10
5/64
0.036
6
0.1380
0.1380
0.1329
0.263
0.097
0.013
0.096
TX-15
5/64
0.066
8
0.1640
0.1640
0.1585
0.311
0.112
0.014
0.111
TX-20
3/32
0.076
10
0.1900
0.1900
0.1840
0.359
0.127
0.015
0.145
TX-25
1/8
0.087
1/4
0.2500
0.2500
0.2435
0.480
0.161
0.016
0.183
TX-30
5/32
0.111
5/16
0.3125
0.3125
0.3053
0.600
0.198
0.017
0.216
TX-40
3/16
0.135
3/8
0.3750
0.3750
0.3678
0.720
0.234
0.018
0.251
TX-45
7/32
0.159
7/16
0.4375
0.4375
0.4294
0.781
0.234
0.018
0.291
TX-50
1/4
0.159
1/2
0.5000
0.5000
0.4919
0.872
0.251
0.018
0.372
TX-50
5/16
0.172
5/8
0.6250
0.6250
0.6163
1.112
0.324
0.022
0.454
TX-55
3/8
0.220
3/4
0.7500
0.7500
0.7406
1.355
0.396
0.024
0.454
TX-60
1/2
0.220
7/8
0.8750
0.8750
0.8647
1.604
0.468
0.025
---
---
9/16
0.248
1"
1.0000
1.0000
0.9886
1.841
0.540
0.028
---
---
5/8
0.297

It is not practical to make the edges of the flat socket heads sharp, therefore a minimum head diameter is referenced above. This is the minimum measurement allowed on flat sockets with a rounded or flat edge on the countersink perimeter. The flushness tolerance is the allowable distance between the top of the screw and the surface of the countersink when a hole has been countersunk exactly 82 ° .

Unfortunately there is not a handy formula available to tabulate the minimum thread, grip and body length as with the button socket cap screws. Your sales representative has this information available.

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