Right hand threads are always used on connections for acetylene hoses.

• A. Sometimes
• B. False
• C. True
• D. Depends on manufacturer

Answer: (B)

Gas connections for welding lines are designed so you can’t mix up gases. Acetylene is normally connected with left-hand threads on the cylinder valve side, which means the acetylene hose and regulator fittings are also built to mate with that left-hand standard. The oxygen system, by contrast, uses right-hand threads. Because of this separation, the statement that right-hand threads are always used for acetylene hoses isn’t correct. In practice, acetylene connections are left-handed to prevent accidentally connecting acetylene equipment to an oxygen supply, a critical safety feature. Some variations or adapters exist, but the standard is left-hand threading on the acetylene side.