STS Industrial - Bolts & Screws



ASTM F912 Covers the mechanical and material requirements for alloy steel socket set screws.
ASME B18.3 Covers the complete general and dimensional data for various types of hexagon socket cap screws, shoulder screws and set screws.
ASME B1.1 UNC & UNF Class 3A Specifies the thread form, series, class, allowance, tolerance, and designation for unified screw threads.



Socket set screws are a headless fastener threaded its entire length (except for the point) used commonly for fastening mated parts such as a shaft and collar. They are manufactured from quenched and tempered alloy steel for maximum strength. The socket set screw’s headless design allows the fastener to sit flush, or inset into the threaded part. Different point types are used to fasten to the mated part:

  • Cup Point – Hexagonal drive at one end, cup-shaped indention at the other end. Most common type. Designed for fast, permanent and semi-permanent location of parts on a shaft with a hardness differential of 10-15 Rockwell C points, and where a cutting edge on the shaft is acceptable.
  • Half-Dog Point – Hexagonal drive at one end, protruding tip with a flat face at the other end. Intended for permanent setting. The point should fit closely to the diameter of the drilled hole or against the flat. Commonly used in place of a dowel pin.
  • Oval Point – Hexagonal drive at one end, oval-shaped point at the other end. The preferred style for frequent installation on shafts with minimum deformation. Also used for permanent installations on shafts that are spotted, splined or grooved, as well as applications where the point meets the shaft on an angle.
  • Flat Point – Hexagonal drive at one end, flat surface at the other end. Used for frequent resetting or relocating on hard steel shafts, and where minimal damage to the shaft is necessary. Shafts sometimes have a spot ground flat for improved contact.
  • Cone Point – Hexagonal drive at one end, conical-shaped point at the other end. Designed for permanent setting on shafts. Deep penetration into the shaft means that this type has the highest torsional and axial holding power. For shafts with hardness greater than or equal to Rockwell C15, spot point half its depth. Can also be used as a pivot or hanger.

Socket Head Cap Screw Head



Cup Point and Half Dog Socket Set Screw Dimensional Data


Oval Point, Flat Point, and Cone Point Socket Set Screw Dimensional Data

Sources: ASTM Standards for Mechanical Fasteners and Related Processes 2nd Edition, Inch Fastener Standards 8th Edition, Kanebridge Fastener Reference Guide 4th Edition

Note: All material included on this page is informational only, and should not be used as one’s sole source for design purposes. STS Industrial, Inc. and its affiliates do not guarantee the accuracy of the information on this site, and retain no liability for the use or misuse of the information contained on this site.