Overview

• Flat undercut head types have a flat surface that begins to taper toward the body but is undercut to allow for shallow countersinking that standard flat head fasteners cannot achieve
• Machine screws without washers can be used with both flat and lock washers
• Phillips drive types have a cross-shaped slot and are used with Phillips drivers
• To prevent damage to the fastener head and fastened surface, the drive design forces the driver to cam out when the fastener is sufficiently tightened
• Steel is strong and durable but less corrosion resistant than stainless steel
• To improve its resistance to corrosion, it may receive additional finishes and coatings.