Opening a chain link can be a useful skill when having to repair or resize a chain for a motor's drive or a bicycle's chain. The first try may be a little daunting, but by following a logical process, it can done quickly and simply.
Place the chain in the vise where the link plate is just above the top of the vise jaws. The chain should be on its side so the link you want to remove is facing up and towards you.
Use the safety glasses and place them over your eyes as sparks will fly on this next step. Use the grinder to grind down the two holding pins on the chain link plate. Grind the pins flush with the surface of the chain link. The entire link plate should be showing a new shiny metal color.
Take the small punch in hand, the diameter of the punch should be slightly smaller than the chain links pins size. Center the punch on the pins and strike the punch firmly with the hammer. Alternate between the two pins and drive them below the top link plate.
Pry the top link plate with the screwdriver to remove it from the pins.
Remove the chain from the vise and work the remaining part of the chain link from the chain. You may have to wiggle the chain back and forth for the link to come loose from the chain links metal sleeve.