Noise management: Electric drills
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Electric drills vary in noise output according to type. Hammer drills produce the highest noise levels because of their impact function. The quality and method of construction of the drill also determines the amount of noise it will produce. Quality tools with ball-bearing races are quieter than tools with phosphor bronze brushings. The quietest form of drill is the cordless variety, which produces around 78 dB(A). The normal hand held drill produces between 90 and 94 dB(A) and hammer drills produce in excess of 100 dB(A). Hearing protection should be worn when operating mains powered electric drills.
- When servicing the tool have the bearings/bushings and brushes checked for wear.
- Bearings or bushings are located in the gearbox and at the rear of the motor unit. You can check for gearbox wear by grasping the chuck and testing for side to side movement. In a normal drill end play can also be checked, hammer drills normally have movement in this direction.
- Excessive sparking from the motor usually indicates worn brushes. If brushes are not replaced, expensive damage to the commutator can result.
- Have all worn parts replaced. Regular maintenance not only reduces the noise but also extends the life of the tool.
- Use sharp drill bits. Blunt drill bits squeal and produce more noise.
- Use appropriate drill speed suited to the particular task and type of drill bit being used.
- Use the hammer action on masonry only when normal drilling action is ineffective.
- Do not force the tool by using excessive pressure. Let the drill bit work through the material.
- When drilling metal, ensure metal is firmly clamped near drilling area.
- Ensure sheet metal is adequately damped to prevent vibration. Small sandbags strategically placed on large sheets or against metal boxes can help reduce the noise produced.
- Increase distance from operator's head to drill, to lower noise received at the ear.
- When replacing a drill specify noise level requirements of less than 85 dB(A).
- Use a pedestal drill or cordless drill where possible.
- Repetitive drilling in a tin plate can be replaced with a small lever and cam operated press with a die to suit the hole size.
Adapted from the Noise Control Manual for Schools with the permission of the Education Department of Western Australia.
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