Instead of putting another shaft on a golf club, most golfers decide to buy another club. But it is easy and less expensive to replace the shaft.
Remove the old shaft. It can be done by melting the glue, or epoxy, that holds the shaft to the head of the club. Use a blowtorch or a heating gun for this purpose. Aim it at the hosel--the connecting part of the head--until the epoxy softens and you can easily remove the shaft.
Cut the shaft to the proper length, depending on what club you are modifying. There are websites that can help you determine the length.
Roughen the tip of your new shaft before inserting it into the hosel of the club head. If the shaft is made of steel, use a piece of sandpaper. If you are inserting a graphite shaft, it would be best to use a belt sander because you can easily damage it by using sandpaper. Also, rid the residue of the old epoxy for the hosel by using a wire drill bit.
Apply epoxy to the tip of the shaft and the inside of the hosel of the club head, and insert the shaft into it. Make sure all surfaces of both are covered. To seat the shaft, rotate it inside the hosel, then tap the butt end of the shaft against a firm object to make sure it is in.
Prepare the shaft for its new grip. Place double-sided tape on the shaft where the grip will be placed and soak it with grip solvent. Pour a small amount inside the grip, then swirl it around until it is completely covered. Pour out the remaining solvent onto the double-sided tape, then put on the grip, making sure it is firmly set on the butt of the club. Adjust the grip to your specifications during the 15 minutes or so it takes for the grip solvent to dry.