Hex Cap Screws
A hex cap screw is a six-sided bolt with a trimmed hex head and a washer face on the bearing surface. It must meet specific tolerances as described under ASME B18.2.1-1996. Hex cap screws are commonly used in OEM applications where precise tolerances are needed. The most common hex screw specifications include ASTM A449 and SAE J429 Grade-2, Grade-5, and Grade-8.
As a wholesale supplier of hex cap screws, AFT Fasteners carries over 20,000 different screw sizes and styles, including lengths up to 36” in plain, hot dipped galvanized, and zinc finishes. The cap screws are also available either partially or fully threaded.
Hex Cap Screw Head Markings
Hex Cap Screws vs Hex Bolts
Hex cap screws are often mistakenly called hex bolts, though the main difference is that hex cap screws feature a washer face under the head and a chamfered point, and a hex bolt does not have a washer face or chamfered threads.
Cap screws are normally used without a nut and are tightened directly into a tapped or threaded hole. Common cap screw head styles include: hex head cap screws, socket head cap screws, button head cap screws, flat socket head cap screws and low profile socket head cap screws.
Hex Cap Screw Classifications
Steel and stainless steel hex cap screws are classified by grade for SAE or property class for metric. Product standards require the manufacturer’s head marking to appear on the top of all hex cap screws ¼” diameter and larger.
Grade-2 Hex Cap Screws
Made from a low or medium carbon steel and is an economical choice for use in non-critical applications where the screw is not subject to extreme temperatures or stress.
Grade-5 Hex Cap Screws
Made from medium carbon steel and heat-treated. They have a greater tensile strength than Grade-2 screws.
Grade-8 Hex Cap Screws
Made from medium carbon steel and heat-treated. They have a greater tensile strength than a Grade-5 screw, and designed for use in high stress applications.
Stainless Steel 18-8 & 316 Hex Cap Screws
Both 18-8 and 316 stainless steel hex cap screws are made from austenitic alloys. 18-8 stainless steel screws are used in products that require general atmospheric corrosion resistance, such as with chemicals and food processing equipment. 316 stainless steel screws have a higher resistance to corrosion and have superior strength at high temperatures.
Class 8.8 Hex Cap Screws
Made from medium carbon steel and heat treated. Class 8.8 screws have greater tensile strength than classes 4.6, 4.8 and 5.8 cap screws.
Class 10.9 Hex Cap Screws
Made from medium carbon alloy steel and heat treated. Class 10.9 screws have greater tensile strength than Class 8.8 cap screws. It is most comparable but not exactly equivalent to U.S. Grade 8 cap screws.
Hex Cap Screw Resources:
- Hex Cap Screw Dimensions & Specifications
- Nut Compatibility Chart
- Bolt Grade Markings & Bolt Strength Chart