A flat head socket cap screw is a threaded fastener with a flat, countersunk head designed to sit flush with the surface of an assembly once installed. Its internal hex drive allows for high torque application in tight or recessed spaces where a standard screwdriver won't fit. KD Fasteners manufactures flat head socket cap screws in both standard and custom sizes, across a wide range of materials, for industries that need a clean, low-profile fastening solution without sacrificing strength. Whether you need an off-the-shelf size or a fully custom spec, our in-house capabilities support both.

Flat Head Socket Cap Screw Features & Design

Unlike a button head or pan head screw, a flat head socket cap screw is designed to countersink into the mating material, leaving no protrusion once fully seated. This makes it ideal for applications where a flush, low-profile surface is required. Note that head markings, such as manufacturer or grade stampings, may appear on top of the head depending on material and specification.

Flat head socket cap screws are manufactured with one of two head angles, depending on the governing standard: an 82° angle for inch-based screws (ANSI/ASME B18.3), or a 90° angle for metric screws (ISO 10642 / DIN 7991). The internal hex drive provides better torque transfer and reduces cam-out compared to slotted or Phillips drive styles, making installation faster and more reliable.

Flat Head Socket Cap Screw Standards & Specifications

KD Fasteners manufactures flat head socket cap screws to meet ANSI/ASME B18.3 (inch) and ISO 10642/DIN 7991 (metric) specifications, in standard and custom sizes to fit your application. We offer a broad range of diameters, lengths, and thread pitches, and can produce fasteners to your exact drawing or print specifications when standard sizing won't work.

Flat Head vs. Button Head, Low Head & Hex Cap Screws

"Cap screw" is a general term for a fully threaded fastener with a machined head, tightened with a wrench or driver rather than a nut. A flat head socket cap screw is one style within that category, distinguished by its countersunk profile and internal hex drive.

Compare that to a button socket cap screw, which has a low-profile dome head that sits above the surface; a low head socket cap screw, used when head height needs to be minimized without countersinking; or a hex cap screw, which uses an external hex head for wrench-driven installation.

Flat Head Socket Cap Screw Materials

Stainless Steel Flat Head Socket Cap Screws

Excellent corrosion resistance and durability, making these a reliable choice for outdoor, marine, and general industrial applications.

Alloy Steel Flat Head Socket Cap Screws

High strength and wear resistance for demanding structural and mechanical applications, commonly used where load-bearing capacity matters more than corrosion resistance.

Titanium Flat Head Socket Cap Screws

Comparably strong as steel but 45 percent lighter, titanium is one of the world's most versatile metal alloys, keeping parts secure in demanding environments.

Inconel Flat Head Socket Cap Screws

Built to withstand extreme heat and corrosive environments, ideal for aerospace, oil and gas, and high-temperature industrial use.

Aluminum Flat Head Socket Cap Screws

Lightweight and corrosion-resistant, a practical choice when reducing overall assembly weight is a priority.

Monel Flat Head Socket Cap Screws

Highly resistant to seawater and acidic environments, well-suited for marine and chemical processing applications.

Flat Head Socket Cap Screw Applications & Industries

Flat head socket cap screws are used wherever a flush, low-profile fastener is required without compromising holding strength — including aerospace, automotive, electronics, and general industrial machinery. Their countersunk design makes them a common choice for panels, enclosures, and components where surface clearance or appearance matters.

Need a Custom Flat Head Socket Cap Screw?

KD Fasteners manufactures flat head socket cap screws in standard and fully custom sizes, materials, and specifications — no minimums required. Our in-house engineering and manufacturing capabilities mean we can match your exact drawing, print, or application requirement.

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Flat Head Socket Cap Screw FAQ

What is a flat socket head cap screw?

A flat socket head cap screw is a threaded fastener with a flat, countersunk head and an internal hex drive, designed to sit flush with the surrounding surface once installed.

What are screws with flat heads called?

Screws with flat, countersunk heads are commonly called flat head screws. When paired with an internal hex drive, they're known as flat head socket cap screws.

What is the difference between a cap screw and a socket cap screw?

A cap screw is any fully threaded fastener with a machined head tightened with a tool. A socket cap screw is a specific type of cap screw that uses an internal hex (socket) drive.

How do you measure a flat head socket cap screw?

Measure the diameter, thread pitch, and length from under the head to the tip of the screw, since the head is designed to sit flush and isn't included in the length measurement.