3M™ Roto Peen Mandrel 7210, 1 ea/Case

The 3M Roto Peen Mandrel is a specialized tool designed to provide efficient repair and maintenance to U.S. Army helicopters. It is used to repair components such as rotors and rotor hubs in the field. The mandrel, along with its associated flap assembly, allows for peening action using a die grinder or disc sander. This tool was qualified and written into military specifications in the early 1970s and has since been widely adopted in the aerospace industry.

Today, the mandrel and flap assembly are primarily used for aerospace applications. The assembly consists of tungsten carbide shot bonded to a flexible polymeric flap, which is gripped by the mandrels attached to a power tool. When the flap spins, the captive shot hammers the metal surface with each revolution, effectively repairing metal surfaces through captive shot peening.

The 3M flap/mandrel assemblies are portable and can reach both small areas and large components. They are especially effective for precision in-service rework, manufacturing, and repair of small areas. The assemblies can peen holes with diameters as small as 1/2 inch (12.7mm) and can be cut with scissors to peen confined areas or areas with a radius as small as 1/16 inch (1.6mm).

Captive shot peening is used when repair or limited access work is required, or when free shot cannot be tolerated. By using captive shot in a flap assembly, there is more control and greater access to areas that require strengthening through peening.

Peening is a process that has evolved from the days of blacksmiths hammering swords. It utilizes compressive surface stress to strengthen metals, improving their resistance to fatigue fracture and stress corrosion cracking. The aerospace industry has stringent peening specifications, and adherence to these specifications must be frequently documented to ensure the quality and reliability of parts. To measure peening intensities, 3M also provides Almen gauges, which provide precise readings of strip deflections. The Almen Scale of Peen Intensity, adopted by the SAE (Society of Automotive Engineers), measures the curvature of a standardized steel strip when peened on one side.