Powder-actuated Tool

A powder-actuated tool (often called a "Hilti gun" or a "Ramset gun" after their manufacturing companies) is a nail gun used in construction and manufacturing to join materials to hard substrates such as steel and concrete. Known as "direct fastening", this technology relies on a controlled explosion created by small chemical propellant charge, similar to the process that discharges a firearm.

Powder-actuated tools come in either high velocity or low velocity types. In high velocity tools the propellant acts directly on the fastener. This process is similar to a firearm. Low velocity tools introduce a piston into the chamber. The propellant acts on the piston, which then drives the fastener into the substrate. (The piston is analogous to the bolt of a captive bolt pistol.) A powder-actuated tool is considered to be low velocity if the average test velocity of the fastener does not exceed 492 feet per second (150 m/s). High velocity tools may not be made or sold in the United States, however some made decades ago are still in use in shipbuilding and steel industries.

Powder-actuated fasteners are usually nails made of high quality, hardened steel, although there are many specialized fasteners designed for specific applications in the construction and manufacturing industries.

Powder-actuated technology was developed for commercial use during the Second World War, when high velocity fastening systems were used to temporarily repair damage to ships. In the case of hull breach, these tools fastened steel plates over damaged areas. These tools were developed by Mine Safety Appliances, for the United States Navy. Powder-actuated tools were investigated and used prior to this development; they were used as part of submarine hunting during the First World War and were the subject of a 1921 United States patent (US Patent No. 1365869).