Office chairs and dining chairs are frequently built with casters attached. You can add casters to any chair if the legs are built sturdy enough to support them. Choose a chair with wooden legs at least a quarter-inch thick in each direction. It is best if the chair has horizontal supports no more than any eight inches above the floor as adding casters will put pressure on the legs to spread them.
Turn the chair upside down and brace it on something sturdy so that all four legs are up and flat with each other as they would be with the floor.
Use a quick square to mark the center of each chair leg. Drill a hole in each leg keeping the drill as level as possible. Caster spindles vary from style to style and brand to brand. In general drill the hole to the depth and with the bit size recommended in the caster instructions.
Wrap a piece of masking tape around the bit at a distance from the tip equal to the depth of the hole to make getting the correct depth easy. Do not force the drill, apply steady pressure to the drill and keep the bit as steady as possible. Blow the dust from the hole
Set the spindle sleeve into the hole. Tap it flush with the bottom of the leg using a small hammer or rubber mallet. Repeat the drilling and sleeve installation with all four legs.
Set the caster into the spindle and lock it in place. Use a wrench to attach casters with a nut at the bottom of the axle. Other casters have a spring loaded clip that snaps in place when they are slid into position in the sleeve. For this type a tap or two from a mallet or hammer may be needed to seat the caster completely. Consult the instructions for specific instructions for your casters.