Upset head bolt (+) with integrated washer, P-3

Upset bolt with integrated washer (Sems screw / assembled washer bolt)

This is a (+) upset-type bolt in which a spring washer and a flat washer are pre-assembled, preventing the washers from falling off.

As a result, it eliminates the risk of forgetting to install washers and improves assembly efficiency.

It is also known as a “SEMS screw” or “assembled screw” (組込ねじ).

Depending on the washer combination, there are variants such as P-2 (spring washer only) and P-3 (spring washer + flat washer).

P-3 refers to the type with a pre-assembled spring washer (SW) and flat washer (plain washer) in accordance with JIS standards.

Applicable standards: JIS B 1187, GB9074.13

Note: The integrated washers are standardized components designed to match the bolt body as a unified assembly.