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
• Slotted drive types are used with flat-blade drivers
• They have one linear slot that runs the length of the head
• Drivers must be centered in the slot during tightening or they will slip out and damage the fastener
• 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.