It may be that a work piece is jammed in a a machine and the operator is using both hands to hold it and cannot reach the off switch with his hand. In this case a foot operated stop switch would be beneficial. Remote emergency stop controls can also be helpful in these situations as a workmate can shut down the machines.

Emergency stop controls can also be used to stop machines in the case of cutter problems (band saw breakages, sander belt breakages, circular saws buckled due to lack of tension etc)

All machines that are connected to the emergency circuit must fail safe, in other words must trip to off when the power has been removed due to operation of the emergency switch. This will prevent them re-starting automatically when the emergency circuit is reset.

Consider

Woodworking Machine Safety (Guards and Push Sticks)

Operative Safety

Health and Safety (PPE)

Training (Safe use and setting up)