Reciprocating, pneumatic impact tools have been in existence for decades. Tool modifications in the past have usually been time and labor-intensive iterative processes, often requiring multiple prototypes. Low-vibration hand tools are needed to comply with new industrial hand-arm vibration guidelines. To reduce costs associated with tool redesign and modification, the operation of reciprocating, pneumatic impact tools has been modeled by computer code. Difficulties associated with modeling the vibration response of a tool associated with a rapid succession of impacts occurring without regard to regular time or space intervals have been overcome. The modeled tool compares favorably with experimental data.