Case Study: Bolt Handle

Process: Metal injection molding (MIM)

Material: MIM-4605 low-alloy steel

Density: 7.5 g/cm³ minimum

Hardness: 31-41 HRC

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End Use and Function

This component is a bolt handle for a hunting rifle. The part assists with loading the next round of ammunition and ejecting the shell after it has been fired.

Fabrication

The complex curvature and intricate design of this component presented challenges with molding and sintering. The visual surface had to be free of surface defects. Threads were included in the molding process, eliminating a secondary operation. No secondary machining was required for this part. The parts are made using MIM-4605 low-alloy steel to a density greater than 7.5 g/cm³, heat treated to a hardness of 31 to 41 HRC, and are finished with a flash nitride operation.

Results

MIM processing was able to convert a two-piece design machined from bar stock to a single piece MIM part. The amount of material removed during conventional machining, in addition with the features that required to be cut, prohibited mass manufacturing, and increased cost. This component demonstrates that intricate shapes and geometries can be molded and held within tolerance throughout the process. Designing this as one piece and
incorporating all features, resulted in reduced handling, lead-time, and cost, while providing a process that met high-volume requirements.