Damaged or broken spindles on your stair rail can be dangerous, not to mention unattractive. Fortunately, it takes very little effort to replace a broken or damaged spindle. The most difficult part of the job may be finding a matching replacement. Bring the damaged wood spindle to a carpenter or mill worker so they can match the original. For iron spindles, a blacksmith should be able to help you. Once you have tracked down the correct parts, the rest will be easy.
Cut the damaged spindle in half with a jigsaw. For iron balusters, fit your jigsaw with a metal cutting blade.
Grab onto the top half of the spindle firmly with both hands. Wiggle the spindle around until you loosen it from the top rail. Repeat this action with the bottom half of the spindle.
Check inside the holes at the top and bottom rail for nails and dried adhesive. Use a chisel to break up any dried adhesive and the pliers to remove the debris from the hole. Pull out any nails with the pliers.
Measure the distance from the top rail to the bottom. Measure the depth of both installation holes. Cut the new spindle with a circular saw. For iron balusters, install a metal cutting blade in your saw. Trim the spindle from the bottom to match the length of the spindle plus the depth of the top and bottom installation holes.
Mix two-part epoxy according to manufacturer's directions. Place the epoxy in an epoxy gun. Fill the bottom hole about half way with the epoxy.
Slide the top of the spindle into the hole in the top rail. Place the bottom of the spindle into the epoxy-filled hole in the bottom rail. Check that the rail is level and let the epoxy set.
Squirt epoxy into the space between the top rail and the spindle. Let the epoxy set.
Iron spindles come with an iron shoe that will fit over the spindle and sit flush with the top and bottom rail. This shoe covers the gaps in the installation hole. Slide it onto the spindle before installation. Fill gaps in wooden spindles with wood filler and smooth with your finger.