Non-standard machine screws and standard screws differ in their design, size, and application：

Design: Standard screws follow established industry standards, such as the American National Standards Institute (ANSI) or International Organization for Standardization (ISO). These standards define the dimensions, thread pitch, and other specifications of the screw. Non-standard machine screws, on the other hand, do not adhere to these established standards and may have unique designs or features.

Size: Standard screws come in a wide range of sizes, typically categorized by their diameter, thread count, and length. Non-standard machine screws may deviate from these common sizes and may be custom-made for specific applications.

Application: Standard screws are widely used in various industries and applications, such as construction, automotive, and electronics. They are readily available and interchangeable, making them convenient for general use. Non-standard machine screws, however, are often designed for specialized applications where standard screws may not meet the specific requirements. These screws may be used in unique machinery, equipment, or custom projects.