FF-S-85 Cap Screws — Slotted and Hexagon Head
The specification for FF-S-85 cap screws covers both slotted cap screws and hexagon head cap screws. These general-purpose externally threaded Federal Specification fasteners are designed to be joined directly into a tapped hole without the need for a separate nut. This specification officially superseded the earlier FF-S-91 standard and continues to be updated, currently standing at FF-S-85 revision F.
At a Glance
FF-S-85 Cap Screws Overview
FF-S-85 cap screws are highly controlled, externally threaded fasteners intended to be driven directly into a tapped hole in one of the parts being joined. Because a cap screw's head bears directly against the top part while its threads engage the bottom part, thread engagement length and head-bearing strength are both critical dimensional requirements governed by the specification.
Having superseded the older FF-S-91 documentation, the active FF-S-85 standard sits alongside two closely related Federal Specification fasteners: FF-S-86 (socket-head cap screws) and FF-S-92 (slotted, cross-recessed, or hexagon head machine screws). Together, these three documents cover the bulk of general-purpose cap and machine screw hardware sourced by military and infrastructure contractors today. Detailed historical updates can be found on the Defense Logistics Agency (DLA) QuickSearch index.
Material Grades and Applications
Sourcing these specific components requires strict adherence to material properties to ensure they handle dynamic loads. Standard hexagon head cap screws are typically milled from high-tensile carbon steel or corrosion-resistant steel (CRES), depending on environmental exposure. By contrast, slotted cap screws are often utilized in applications where specialized flat-blade torque tools are required, while the hex variations allow for high-torque socket wrenching in confined mechanical assemblies.
Related Cap & Machine Screw Specifications
| Specification | Head / Drive Style |
|---|---|
| FF-S-85 | Slotted and Hexagon Head Cap Screws |
| FF-S-86 | Socket-Head Cap Screws (hex or spline socket) |
| FF-S-92 | Slotted, Cross-Recessed, or Hexagon Head Machine Screws |
Choosing between FF-S-85, FF-S-86, and FF-S-92 mainly comes down to head/drive style and torque requirements. Hex and slotted cap screws (FF-S-85) suit general assembly, socket-head variations (FF-S-86) suit high-torque or recessed applications, and machine screws (FF-S-92) suit lighter-duty threaded assembly with a mating nut.
Frequently Asked Questions
What's the difference between a cap screw and a machine screw?
A cap screw is designed to be driven directly into a tapped hole and typically has a larger, more precisely controlled head bearing surface for higher clamping loads. A machine screw is generally lighter-duty and often paired with a separate nut.
What head styles does this specification cover?
It specifically covers slotted head and hexagon head cap screws. For socket-head (hex or spline recess) variations, refer to the related specification FF-S-86 instead.
Need FF-S-85 Cap Screws to Print?
Ananka Fasteners manufactures compliant slotted and hexagon head cap screws with full material traceability and Mill Test Certification.
Prefer email? sales@anankafasteners.com
