Operating Controls and Switches
Momentary-Contact "On-Off" Controls
A momentary-contact “on-off” control requires the worker to deliberately activate the control to start the power tool.
Under normal operation, the tool continues running while the control is activated and stops when the worker releases the control. This provides an important safety feature because the operator can stop powered operation without having to make a separate movement to an off switch.
OSHA permits some tools to have a lock-on control. When the lock-on feature is engaged, the tool may continue operating after the worker releases the momentary-contact control. However, OSHA requires the lock-on control to be designed so that it can be turned off by a single motion of the same finger or fingers used to turn it on.
Click on the link to see the list of hand-held powered tools that must be equipped with a momentary-contact “on-off” controls.
- Drills
- Tappers
- Fastener drivers
- Horizontal, vertical, and angle grinders with wheels greater than 2 inches in diameter
- Disc sanders
- Belt sanders
- Reciprocating saws
- Saber saws
- Other similar operating powered tools
Constant-Pressure Switches
A constant-pressure switch provides a stronger automatic shutdown function: the worker must maintain pressure on the control for the tool to continue operating. Release the pressure, and power shuts off.
Portable circular saws and chain saws are familiar examples. The operator must maintain pressure on the trigger while making the cut. If the operator releases the trigger, the saw's power shuts off. This type of control is particularly important on tools where continued powered movement after the operator releases the control could create a serious hazard.
The link below lists identifies tools that require constant-pressure switches.
- Circular saws
- Chain saws
- Percussion tools without positive accessory-holding means such as chipping/riveting hammers, jack hammers, concrete breakers, and rock drills.
Knowledge Check Choose the best answer for the question.
2-4. Which tools must have a constant-pressure switch that shuts off power when released?
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