Overview

A “Non-standard Part Carbon Steel Flat Round Head Long Shank Machine Screw” typically refers to a custom-manufactured fastener with specific characteristics tailored to a unique application, rather than a mass-produced, off-the-shelf item governed by common industry standards (like ISO, DIN, ANSI). Let’s break down what each part of this description implies:

• Non-standard Part: This is the key differentiator. It means the screw’s dimensions (thread size, length, head diameter, shank length, etc.), material grade, finish, or other features do not conform to established industry standards. It’s custom-engineered for a particular purpose, often due to unique assembly requirements, aesthetic demands, or performance specifications that standard screws cannot meet. This usually involves higher tooling costs and minimum order quantities compared to standard parts.
• Carbon Steel: This indicates the material from which the screw is made. Carbon steel is a common choice for fasteners due to its excellent strength, durability, and cost-effectiveness. The specific grade of carbon steel (e.g., 1018, 10B21, 4140) would be specified by the customer based on the required mechanical properties (tensile strength, hardness, etc.). Carbon steel fasteners are often treated with a protective coating (like zinc plating, black oxide, or phosphate) to prevent corrosion.
• Flat Round Head: This describes the head style of the screw. It’s a combination that typically means:
  • Round Head: A dome-shaped head, often used when an aesthetic, smooth, and low-catch surface is desired. It doesn’t sit flush with the surface but protrudes with a gentle curve.
  • Flat (implied for top surface): While a “round head” is inherently rounded, the “flat” might refer to the bearing surface underside the head (though less common for a pure round head) or imply a slightly flattened apex compared to a perfectly spherical dome. More commonly, “flat round head” might be a colloquial way to describe a pan head or an oval head (which has a slightly countersunk conical underside and a rounded top). Without a drawing, definitive interpretation is difficult, but it suggests a desire for a relatively low-profile, smooth, rounded head.
• Long Shank: This refers to the length of the unthreaded portion of the screw’s body (the shank). A “long shank” implies that there’s a significant length of the screw that is smooth and unthreaded before the threaded section begins, or that the overall length of the screw is substantial, with a proportionally long unthreaded section. This can be important for:
  • Clearance: Allowing parts to rotate freely on the smooth shank without thread wear.
  • Alignment: Guiding components into position before threads engage.
  • Shear Strength: The unthreaded shank often offers higher shear strength than the threaded portion.
  • Specific Application Depth: Needing to pass through thick material before engaging a nut or threaded hole.
• Machine Screw: This denotes the type of thread and intended use. Machine screws have uniform threads along their length (or a portion of it) that are designed to mate with a pre-tapped hole or a nut. They are typically used for connecting metal parts, or metal parts to plastic, where a precise and strong connection is needed. Unlike self-tapping or wood screws, machine screws require a pre-formed female thread.

Typical Applications & Considerations:

This type of custom screw would be used in applications where standard fasteners don’t quite fit the bill, such as:

• Specialized electronic enclosures or internal components.
• Unique furniture designs requiring specific aesthetics or load distribution.
• Custom machinery or robotic assemblies.
• Prototyping or limited-run manufacturing where standard dimensions are insufficient.

When ordering a non-standard part like this, detailed technical drawings with all dimensions, tolerances, material specifications, heat treatment, and surface finish requirements are absolutely crucial. This ensures the manufactured part precisely meets the specific needs of the application.