R2: Drilling into concrete: Effect of feed force on handle vibration and productivity

Approximately 1.6 million commercial construction workers in the US use rotary hammer drills for drilling into concrete to insert anchor bolts or rebar. The exposure to vibration may lead to hand-arm vibration syndrome and other musculoskeletal disorders depending on handle vibration acceleration level, hand grip force, and duration of exposure. There is little information on the relationship between feed force (FF), e.g., the push force applied by the worker, and handle vibration. A robotic test bench for rotary hammer drills was used to evaluate the effects of different FF on handle vibration and productivity (e.g., penetration rate and holes drilled). Increasing FF from 95 to 163 N was associated with an increase in total weighted handle vibration (a(hv)) of 7.2-8.5 m/s(2) (slope, p < 0.001) but from 163 to 211 N there was no change in vibration level (slope, p=0.17). Increasing FF from 95 to 185 N was associated with an increase in penetration rate of 7.2-8.5 m/s(2) (slope, p < 0.001) but from 185 to 211 N there was no change in penetration rate (slope, p - 0.49). Based on the maximum allowable duration of exposure to hand vibration, specified by the ISO and ACGIH Action Limits, and the penetration rate, the drilling productivity, in m drilled per day, is greatest for the lowest FF tested. Contractors and construction workers should be informed that when drilling into concrete, the lowest exposure to harmful hand vibration and the best overall productivity occurs when the lowest operational FF is applied during hammer drilling.