Which term matches the description of buttress thread properties?

• A. Two types: lead screw type and hydraulic sealing type.
• B. A 60-degree thread angle.
• C. Identical to B.S.C. threads.
• D. Used only for decorative fittings.

Answer: (A)

Buttress threads are built to carry heavy thrust in one direction while easing movement in the opposite direction, achieved by an asymmetrical profile: one flank is nearly vertical to provide a strong load-bearing surface, and the other flank is inclined to reduce resistance when the load would push the engagement the other way. Because of this orientation, they’re not defined by a typical symmetric thread angle like standard V-threads, and they aren’t simply a direct equivalent of British Standard Cycle threads. In practice, you’ll encounter two common forms: a lead screw type, which is used to efficiently convert rotation into linear motion with strong thrust in the driving direction, and a hydraulic sealing type, where the thread also serves to seal against pressure in hydraulic systems. These two forms cover the main applications of buttress threads, rather than decorative uses or matching standard 60-degree V-thread characteristics.