What is spindle lock?
Most cordless drill drivers have a feature called spindle lock. When spindle lock is selected, the motor’s spindle is locked and so the chuck and screwdriver or drill bit cannot turn.
Automatic and manual spindle lock
Most cordless drill drivers have automatic spindle lock, which means that the chuck and bit are automatically locked when the speed control trigger is released.
Other models require you to manually activate spindle lock, usually by sliding the forward/reverse switch into the central position. This will lock the drill OFF.
When to use spindle lock
Loosening or tightening screws
Sometimes, it can be hard to start removing a screw using a cordless drill driver if its very tight. The tool can slip out of the screw head or may not have enough power to start
With spindle lock you can use the cordless drill driver like a manual screwdriver, controlling the pressure on the screw and the speed at which you loosen it.
Spindle lock can also be used to finish off the tightening of a screw, so that you don't drive it too far into the surface of the material.
Inserting or removing bits
Selecting spindle lock allows you to insert or remove screwdriver or drill bits without worrying about the chuck rotating and causing injury.