Hex cap nut (acorn nut)

Cap nut (acorn nut)

A cap nut is a type of nut with a blind (closed-end) threaded cavity, where one end is sealed like a dome.

It is commonly used to cover exposed bolt ends, improving safety and enhancing appearance.

Also known as a cap nut.

Applicable standards:

• JIS B 1183 (Type 3-2)
• DIN 1587
• IFI (U.S. standard)
• GB 802.1
• GB 923

JIS classification:

• Type 1: one-piece hex body and cap, without thread relief
• Type 2: one-piece construction with thread relief
• Type 3: hex body with welded cap

In practice, the most commonly used type is Type 3-2. (3形2種).
“Type 2” refers to the base hex nut type (double chamfered type).