Head Styles for Self Tapping Screws

Head Style	Description	Application & Advantages
Bugle	A countersunk head with a flat top and a concave underhead bearing surface.	Designed specifically fo use in drywall. Distributes bearing stress over a wider area than flat heads.
Pan	Slotted pan heads have a flat or gently rounded top surface, cylindrical sides and a flat bearing surface. Phillips, Torx® and square pan heads have a rounded top surface, cylindrical sides and a flat bearing surface.	For general applications. Can be substituted in most applications for round, truss or binding heads.
Flat 82°	A countersunk head with a flat top surface and a cone-shaped bearing surface with a head angle of approximately 82°.	Used in applications where protrusion of the fastener above the mating sufrace is unaccepttable. Use a protrusion gage when measuring head height.
Flat Undercut	Similar to an 82° flat head except that the head is undercut to 70% of its normal side height.	Standard for short lengths because it allows greater length of threads. Also avoids transition fillet and assembly interference.
Indented Hex	Has an indented top surface, six flat sides, and a flat bearing surface.	Preferred in high volume assembly where pneumatic equipment is uded to drive the screw. Can transmit significantly higher tightening torque levels than other head styles.
Indented Hex Washer	Has an indented top surface, six flat sides with a flat washer which projects beyond the sides and provides a flat bearing surface. The washer and hex are formed together as one piece.	Increased bearing surface reduces likelihood of crushing mating surfaces.
Serrated Hex Washer	Same as an indented Hex Washer Head but with serrations formed into the bearing surface on the underside of the washer.	Serration geometry is oriented to resist loosening. Also slows the screw at the point of engagement with the mating piece of sheet metal so as to minimize stripping.
Truss	Has a rounded top with a flat bearing surface greater in area than a round head screw of the same nominal size.	Weaker than pan or round heads but preferred in applications where minimal clearance exists above the head. Truss profile provides a trim finished appearance.
Wafer	A countersunk head with a flat top surface and a cone-shaped bearing surface. The wafer's 70° conical underhead area does not extend to the outer edge of the head, providing a bearing surface of 16° aroung the circumference of the underhead.	Preferred head style for Type-CSD self drilling screws. Provides the necessary bearing surface and flush fit in wood and softer materials. The head/shank fillet is contoured to strengthen the underhead area.
Oval	A countersunk head with a rounded top surface and a cone-shaped bearing surface of approximately 83°.	Preferred over a flat head in conical applications, or when a more decorative finished look is desired. The countersunk surface nests into mating countersunk application sites.
Oval Undercut	Similar to an 82° oval head except that the head is undercut to 70% of its normal side height.	Standard for short lengths because it allows greater thread length.
Round (U-drive)	Has a semi-elliptical top surface and a flat bearing surface.	Standard head style for drive screws. Provides efficient non-torque fastening for high-speed assembly.

Head Styles for Self Tapping Screws

See also: Self-Tapping Drive Types