Countersunk hex socket bolt (flat head / conical head)

Countersunk hex socket bolt (countersunk cap screw / flat head)

This is a type of bolt with a conical (countersunk) head and a hex socket drive.

When a countersunk hole is machined into the component, the bolt head sits flush with the surface after installation, providing a clean and aesthetic finish.

It is tightened using an Allen key (hex key) and allows higher tightening torque compared to (+) Phillips head screws, ensuring a strong and secure joint.

Also known as a countersunk cap screw.

Applicable standards:

JIS B 1194
DIN 7991
ANSI/ASME B18.3F

In Japan, this type mainly follows two standards:

SSS (Socket Screw Industry Association standard)
JIS

These two systems have slight differences in head dimensions, so they should not be mixed to avoid assembly issues.