Square head set screws are the wrench-driven members of the set screw family: a solid square head sits above the threads, sized to take an open-end wrench or socket so the screw can be seated and re-seated with real torque, again and again. That external head is the whole point — where a socket set screw disappears into its hole, a square head stands proud and stays serviceable. They survive today in machine-tool setups, agricultural equipment, and anywhere a set screw gets adjusted for a living.
The table below gives the complete head dimensions for inch square head set screws per ANSI/ASME B18.6.2, from #10 through 1-3/8″ — including the neck relief and head radius columns that most published charts leave out. These head dimensions apply regardless of point style (cup, cone, flat, oval, or dog point). Cold Headers has stocked and distributed square head set screws since 1962, across the full diameter range and in multiple point styles and materials.
Square Head Set Screw Head Dimensions — ANSI/ASME B18.6.2 (inches)
| Nominal Size |
F Width Across Flats |
G Width Across Corners |
H Head Height |
K Neck Relief Diameter |
S Neck Relief Fillet Radius |
U Neck Relief Width |
W Head Radius |
||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Max | Min | Max | Min | Max | Min | Max | Min | Min | Min | Min | |
| #10 | 0.188 | 0.180 | 0.265 | 0.247 | 0.148 | 0.134 | 0.145 | 0.140 | 0.027 | 0.083 | 0.48 |
| 1/4 | 0.250 | 0.241 | 0.354 | 0.331 | 0.196 | 0.178 | 0.185 | 0.170 | 0.032 | 0.100 | 0.62 |
| 5/16 | 0.312 | 0.302 | 0.442 | 0.415 | 0.245 | 0.224 | 0.240 | 0.225 | 0.036 | 0.111 | 0.78 |
| 3/8 | 0.375 | 0.362 | 0.530 | 0.497 | 0.293 | 0.270 | 0.294 | 0.279 | 0.041 | 0.125 | 0.94 |
| 7/16 | 0.438 | 0.423 | 0.619 | 0.581 | 0.341 | 0.315 | 0.345 | 0.330 | 0.046 | 0.143 | 1.09 |
| 1/2 | 0.500 | 0.484 | 0.707 | 0.665 | 0.389 | 0.361 | 0.400 | 0.385 | 0.050 | 0.154 | 1.25 |
| 9/16 | 0.562 | 0.545 | 0.795 | 0.748 | 0.437 | 0.407 | 0.454 | 0.439 | 0.054 | 0.167 | 1.41 |
| 5/8 | 0.625 | 0.606 | 0.884 | 0.833 | 0.485 | 0.452 | 0.507 | 0.492 | 0.059 | 0.182 | 1.56 |
| 3/4 | 0.750 | 0.729 | 1.060 | 1.001 | 0.582 | 0.544 | 0.620 | 0.605 | 0.065 | 0.200 | 1.88 |
| 7/8 | 0.875 | 0.852 | 1.237 | 1.170 | 0.678 | 0.635 | 0.731 | 0.716 | 0.072 | 0.222 | 2.19 |
| 1 | 1.000 | 0.974 | 1.414 | 1.337 | 0.774 | 0.726 | 0.838 | 0.823 | 0.081 | 0.250 | 2.50 |
| 1-1/8 | 1.125 | 1.096 | 1.591 | 1.505 | 0.870 | 0.817 | 0.939 | 0.914 | 0.092 | 0.283 | 2.81 |
| 1-1/4 | 1.250 | 1.219 | 1.768 | 1.674 | 0.966 | 0.908 | 1.064 | 1.039 | 0.092 | 0.283 | 3.12 |
| 1-3/8 | 1.375 | 1.342 | 1.945 | 1.843 | 1.063 | 1.000 | 1.159 | 1.134 | 0.109 | 0.333 | 3.44 |
Reading the Columns
F — Width Across Flats. The wrench size. On square head set screws the flats run essentially equal to the nominal screw diameter — a 1/2″ screw takes a 1/2″ wrench opening. This is the quickest way to identify one on the bench.
G — Width Across Corners. The diagonal of the square head — what you need for clearance when the head spins. Roughly 1.4× the flats.
H — Head Height. Measured from the top of the head to the bearing surface under it.
K, S, U — Neck Relief. The turned-down groove between head and threads: K is its diameter, U its width, S the fillet radius where it blends. These columns are specified in B18.6.2 but rarely published — they matter when the screw seats in a counterbore or against a boss and the neck needs clearance.
W — Head Radius. The crown radius on top of the head, approximately 2.5× the nominal diameter.
Where to Go From Here
We stock square head set screws across this size range in multiple point styles — cup, cone, flat, oval, half dog, and full dog — with cup point the everyday standard. Browse the family and current sizes here:
- Square Head Set Screws — Selection Guide — which point style for which job, and how square heads earn their keep next to socket sets.
- Square Head Set Screws in the Catalog — live sizes by diameter, thread, and point.
- Hard-to-Find Fasteners — odd diameters, unlisted lengths, and in-house modification services. If the size you need isn’t in the table above, this is the page to read next.
Need a size verified against the standard, or a square head in a material or point style you don’t see listed? Call us or send the requirement through the quote form — checking a dimension against the drawer is what we do all day.
Dimensions per ANSI/ASME B18.6.2. Values shown are for standard inch square head set screws; always confirm critical dimensions against the governing standard revision for your application.