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Cap Screws

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Alloy steel socket head screws are fasteners made from alloy steel, a type of steel that includes various elements (such as chromium, molybdenum, or nickel) to enhance certain properties like strength, hardness, and corrosion resistance.

Mil. Spec. Alloy Steel Socket Head Screws

These specifications ensure that the screws can withstand extreme conditions and perform reliably in critical applications.

Torx Alloy Steel Socket Head Screws

These screws are used in applications where high torque transmission and reduced risk of cam-out (slippage) are essential.

Left-Hand Threaded Alloy Steel Socket Head Screws

The left-hand threading is specifically designed to tighten counterclockwise, making these screws suitable for applications where the typical rotational forces would loosen a right-hand threaded screw.

High-Temperature Alloy Steel Socket Head Screws—Grade B7

Grade B7 alloy steel is a chromium-molybdenum steel that is known for its high tensile strength and excellent resistance to both heat and wear.

18-8 Stainless Steel Socket Head Screws

The term "18-8" refers to the composition of the stainless steel, which contains approximately 18% chromium and 8% nickel.

Mil. Spec. 18-8 Stainless Steel Socket Head Screws

These screws are designed to meet specific military standards, which define their material properties, dimensions, performance, and quality control measures.

Cleaned and Bagged 18-8 Stainless Steel Socket Head Screws for High Vacuum

These screws are used in critical applications such as vacuum chambers, semiconductor manufacturing, and space technology, where maintaining a clean, contaminant-free environment is essential.

Left-Hand Threaded 18-8 Stainless Steel Socket Head Screws

This stainless steel contains approximately 18% chromium and 8% nickel, providing good corrosion resistance and strength.

Super-Corrosion-Resistant 316 Stainless Steel Socket Head Screws

316 Stainless Steel contains about 16-18% chromium, 10-14% nickel, and 2-3% molybdenum, which gives it enhanced resistance to pitting and crevice corrosion compared to 304 (18-8) stainless steel, especially in chloride-rich environments.

High-Strength A286 Stainless Steel Socket Head Screws

The A286 alloy (UNS S66286) is a precipitation-hardenable, iron-based superalloy that combines the corrosion resistance of stainless steel with the high-temperature strength and creep resistance of nickel-based alloys.

High-Strength 316 Stainless Steel Socket Head Screws

316 stainless steel has a higher content of molybdenum compared to 304 stainless steel, which gives it enhanced resistance to pitting and crevice corrosion, especially in chloride-rich environments such as marine applications.

Plastic Socket Head Screws

These screws provide many advantages over metal screws in specific environments, especially where resistance to moisture, chemicals, or electrical insulation is needed.

Brass Socket Head Screws

Brass is an alloy of copper and zinc, known for its corrosion resistance, particularly in environments with water or humidity, making it ideal for plumbing and marine applications.

Aluminum Socket Head Screws

Aluminum socket head screws are typically made from strong, durable aluminum alloys such as 6061 or 7075, which are known for their excellent balance of strength and corrosion resistance.

Titanium Socket Head Screws

Titanium offers a unique combination of high strength, lightweight properties, and corrosion resistance, making these screws ideal for industries like aerospace, medical, marine, and automotive, where performance and durability in extreme environments are required.

Nickel Alloy Socket Head Screws

A family of nickel-chromium-based superalloys, Inconel (such as Inconel 600, 625, or 718) is known for its excellent oxidation and corrosion resistance at high temperatures.

Bronze Socket Head Screws

The high copper content provides excellent corrosion resistance, while the tin adds strength and durability.

Alloy Steel Low-Profile Socket Head Screws

Despite the low-profile head, they retain the mechanical advantages of standard socket head screws, including the ability to handle high torque.

18-8 Stainless Steel Low-Profile Socket Head Screws

18-8 stainless steel offers excellent resistance to rust, corrosion, and staining, making these screws ideal for outdoor applications or environments exposed to moisture, chemicals, or corrosive elements.

Super-Corrosion-Resistant 316 Stainless Steel Low-Profile Socket Head Screws

This grade of stainless steel contains approximately 16-18% chromium, 10-14% nickel, and 2-3% molybdenum, which provides exceptional corrosion resistance, particularly in chloride and marine environments.

Alloy Steel Ultra-Low-Profile Socket Head Screws

The ultra-low-profile head is thinner than both standard and low-profile socket head screws, providing a minimal protrusion from the surface.

316 Stainless Steel Ultra-Low-Profile Socket Head Screws

316 stainless steel offers superior corrosion resistance, particularly in marine environments, salty air, industrial atmospheres, and areas exposed to chemicals.

High-Profile Socket Head Screws

The extended head height offers more surface area for tool engagement, making it easier to apply higher torque during installation.

Flanged Socket Head Screws

Flanged socket head screws are commonly made from carbon steel or alloy steel for strength and durability in high-stress applications.

Exact-Grip-Length Flanged Socket Head Screws

The exact-grip-length feature ensures that the unthreaded portion of the screw precisely matches the thickness of the material being fastened, preventing threads from contacting the material.

Serrated-Flange Socket Head Screws

The key feature of these screws is the serrated flange, which acts like a built-in washer but with the added advantage of gripping the material.

18-8 Stainless Steel Thread-Locking Socket Head Screws

These screws come with a pre-applied thread-locking compound (such as nylon patch or Loctite) that bonds to the threads upon installation, helping to resist loosening caused by vibration or dynamic forces.

Super-Corrosion-Resistant 316 Stainless Steel Thread-Locking Socket Head Screws

These screws are made from 316 stainless steel, an austenitic stainless steel alloy containing molybdenum, which provides exceptional resistance to corrosion, especially in chloride-rich environments like seawater.

Alloy Steel Thread-Locking Socket Head Screws

Alloy steel is often used in applications requiring the ability to withstand significant mechanical stress. Alloy steel screws are typically heat-treated to improve their hardness and load-bearing capacity.

Stainless Steel Wire-Lockable Socket Head Screws

The defining feature of these screws is one or more small holes drilled through the socket head, allowing safety wire to be threaded through the screw heads of adjacent fasteners. This creates a locking mechanism that physically prevents the screws from loosening or backing out due to vibration or dynamic forces.

Alloy Steel Wire-Lockable Socket Head Screws

Alloy steel is typically heat-treated to increase hardness and strength, making it suitable for high-load environments.The safety wire physically locks the screws in place, preventing them from loosening due to vibration or movement.

Stainless Steel Socket Head Screws with Split Lock Washer

The split lock washer is designed to create friction when compressed during tightening, preventing the screw from loosening due to vibrations or dynamic forces.

Alloy Steel Socket Head Screws with Split Lock Washer

The socket head screws are made from alloy steel, which is a strong and durable material. It typically includes elements such as chromium, molybdenum, or nickel to enhance its strength, hardness, and wear resistance.

Vented Socket Head Screws

This venting allows gases, fluids, or air to escape during fastening, which helps prevent pressure buildup in vacuum, high-pressure, or cleanroom environments.

High-Vacuum Cleaned-and-Bagged Vented Socket Head Screws

These screws are vented, allowing gases, fluids, or air to escape through a hollow center during tightening, and are packaged in clean, controlled environments to prevent recontamination.

Sealing Socket Head Screws

Sealing socket head is typically an O-ring made of elastomeric material such as silicone, Viton, EPDM, or fluorocarbon rubber. This O-ring is positioned under the head of the screw, and it compresses against the surface of the material being fastened when the screw is tightened.

Socket Head Screws with Flat Washer

The flat washer distributes the load of the screw across a larger surface area, reducing the pressure on the material being fastened. This prevents the material from deforming, cracking, or getting damaged under the clamping force.

Vibration-Resistant Sealing Socket Head Screws

These screws combine the benefits of a sealing element, such as an O-ring or gasket, with features that enhance their resistance to loosening due to vibrations or dynamic forces. They are used in applications where both sealing and vibration resistance are critical, such as in automotive, aerospace, marine, and heavy machinery environments.

Nylon-Tip Alloy Steel Socket Head Screws

The nylon tip prevents the hard steel of the screw from directly contacting the material being fastened, reducing the risk of scratching, denting, or otherwise damaging delicate surfaces.

Brass-Tip Alloy Steel Socket Head Screws

The brass tip ensures that the screw can make secure contact with the material being fastened without causing damage, making it ideal for soft or delicate surfaces such as polished metals, plastics, or finished woods.

Socket Head Screws for Square-Drive Wrenches

The square recess in the screw head provides four points of contact with the square-drive wrench or bit, allowing for better torque application and reducing the risk of cam-out (slipping of the tool out of the screw).

LILY Bearing stocks 7,726 socket head cap screws (also called Allen screws) across alloy steel, stainless steel, and specialty materials, with low-profile, flanged, thread-locking, and other feature variants. Use the filters below, or the comparison tables, to narrow down by material, head height, thread size, and length.

Compare by Material

Material	Best For
Alloy Steel	General-purpose machinery and equipment needing high strength
Grade B7 Alloy Steel	High-temperature service up to 1,100°F (per ASTM A193)
18-8 Stainless Steel	General corrosion resistance for a wide range of applications
316 Stainless Steel	Highly corrosive environments, including marine and chemical exposure
A286 Stainless Steel	Engines and turbines needing strength comparable to alloy steel with the corrosion resistance of 18-8
Titanium	High-performance applications needing an excellent strength-to-weight ratio
Brass	Good corrosion resistance with an attractive appearance
Bronze	Marine environments needing corrosion resistance and durability
Aluminum	Lightweight applications where reducing weight is a priority
Nickel Alloy	Resistance to corrosion, high temperatures, and oxidation in harsh environments
Plastic	Environments where metal screws aren't suitable

Most grades are also available as Mil. Spec. variants, and 18-8 stainless steel is available cleaned and bagged for high-vacuum use.

Head Height Options

Beyond the standard socket head, LILY Bearing stocks low-profile and ultra-low-profile heads for tight clearance above the mounting surface, and a high-profile head with extra height for a larger wrenching surface and easier high-torque installation.

Flange Variants

Variant	What It Is
Flanged	A built-in flange spreads clamping pressure over a wider area, eliminating the need for a separate washer
Exact-Grip-Length Flanged	The unthreaded grip length precisely matches the material thickness, so threads never contact the material — ideal where sideways (shear) loads are a concern
Serrated-Flange	Teeth on the underside of the flange bite into the mating surface, adding resistance to loosening under vibration

Anti-Loosening Features

Thread-locking screws have a pre-applied compound (such as a nylon patch or Loctite) on the threads that bonds upon installation to resist loosening. Wire-lockable screws have a small hole drilled through the head so safety wire can be threaded between screws to physically prevent them from turning loose. Screws are also available with a pre-assembled split lock washer, which flattens under compression to add tension that resists vibration.

Application-Specific Variants

Vented screws have a hollow center or small channels that let gases, fluids, or air escape during fastening, preventing pressure buildup in vacuum, high-pressure, or cleanroom environments — high-vacuum cleaned-and-bagged vented screws are also available for the most demanding vacuum applications. Sealing screws use an O-ring positioned under the head to create a tight seal, with vibration-resistant sealing versions combining that seal with added resistance to loosening. Screws are also available with a flat washer pre-assembled to distribute load over a larger surface area.

Drive & Tip Variants

Torx versions use a star-shaped drive for better cam-out resistance than a standard hex key. Square-drive versions have a square recess that locks directly onto a square-drive socket wrench, with no separate bit needed. Nylon-tip and brass-tip versions add a soft, nonmarring tip — nylon is nonconductive and softer, while brass is electrically conductive and slightly harder but still soft enough to protect delicate or finished surfaces.

Left-Hand Threaded

Left-hand threaded socket head screws turn counterclockwise to tighten, for use in counter-rotating assemblies where a standard right-hand thread would work its way loose.

Need a Custom Socket Head Cap Screw?

Don't see the material, head height, or feature you need? Our team can cross-reference an existing part or quote a custom configuration. Request a Quote or Contact Us. LILY Bearing also offers customized fastener services.

Frequently Asked Questions

What is the difference between a flanged and an exact-grip-length flanged socket head screw?

A standard flanged screw simply adds a built-in flange to spread clamping pressure and eliminate the need for a washer. An exact-grip-length flanged screw goes a step further: its unthreaded shank length is precisely matched to the thickness of the material being fastened, so the threads never contact the material and the smooth shank — not the threads — bears any sideways (shear) load. Choose exact-grip-length where lateral forces are a concern.

Should I choose a nylon-tip or brass-tip socket head screw?

Both protect delicate or finished surfaces from metal-on-metal contact. Choose nylon if you need an electrically nonconductive tip or a softer touch; choose brass if you need electrical conductivity or a tip that's slightly harder while still soft enough to avoid marring the surface.