Product Description
1/4"-28 UNF A2 Stainless Steel Socket Cap Head Bolts
These 1/4" UNF socket cap head bolts are manufactured from corrosion-resistant A2 stainless steel and feature a fine 28 TPI Unified National Fine thread. Their cylindrical cap head and internal hexagon socket provide secure tool engagement and allow installation where clearance around the bolt head is restricted.
The bolts are partially threaded, leaving a plain shank between the threaded section and the head. This makes them suitable for assemblies where the unthreaded portion passes through one or more components, helping to provide accurate location and improved resistance to sideways loading.
Product specifications
- Nominal diameter: 1/4" (approximately 6.35mm)
- Thread: 1/4"-28 UNF
- Thread pitch: 28 threads per inch (approximately 0.907mm)
- Material: A2 stainless steel
- Head style: Cylindrical socket cap head
- Drive: Internal hexagon socket
- Hex key size: 3/16"
- Head diameter: Approximately 0.37" (9.40mm)
- Head height: Approximately 0.25" (6.35mm)
- Thread coverage: Part threaded with an unthreaded shank
- Available lengths: 1 1/2", 2" and 3"
Available dimensions
| Overall length | Approx. threaded length | Approx. plain shank | Head diameter | Head height | Hex key |
|---|---|---|---|---|---|
| 1 1/2" | 1.09" | 13/32" | 0.37" | 0.25" | 3/16" |
| 2" | 1.06" | 0.89" | 0.37" | 0.25" | 3/16" |
| 3" | 1.83" | 1.09" | 0.37" | 0.25" | 3/16" |
Overall bolt length is measured from beneath the socket head to the end of the bolt. Dimensions are approximate and may vary slightly between production batches.
A2 stainless steel
A2 stainless steel provides good resistance to moisture, weathering and many everyday corrosive conditions. It is widely used for machinery, workshop equipment, vehicle restoration, fabrication and general engineering assemblies. For marine, swimming-pool or chloride-rich environments, an A4 stainless fastener may be more suitable.
Standards information
The relevant dimensional reference for an inch-series socket head cap screw is ASME B18.3. The 1/4"-28 UNF thread form is covered by ASME B1.1 and the current British Unified-thread standard BS 1580-1:2007.
DIN 912 and ISO 4762 are metric socket-head screw standards and should not be assigned to this imperial UNF product. A specific A2 strength class, such as A2-70, has not been stated and should not be assumed.
These standards are supplied as technical references rather than a claim of independently certified conformity. Where formal certification or a specified stainless-steel property class is required, please confirm availability before ordering.
Typical applications
- Machinery and equipment assembly
- Automotive and motorcycle restoration
- Engineering and fabrication projects
- Outdoor equipment and stainless assemblies
- Fixtures requiring a plain locating shank
- Restricted-access installations using an Allen key
Installation advice
Use a correctly fitting 3/16" hex key or socket bit to minimise damage to the drive. Stainless-steel threads can gall if tightened rapidly or without lubrication, particularly when used with stainless-steel nuts. A suitable anti-seize compound and controlled tightening speed are recommended.
Choose from packs of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 50, 100, 250, 500 or 1,000 bolts.
Browse our complete range of UNF socket cap screws, consult our UNC and UNF thread data guide, or read our guide to preventing stainless-steel thread galling.
