Beautiful wood spiral staircases are a lasting mark of excellence in some of the most luxurious homes in the world. The way the main railings curve and spiral as they go up and down the stairs, it's almost impossible to think someone with limited wood-building knowledge could create such an effect, but it's not as hard as it looks. Following a few tips and special wood techniques, you can create stunning curved wood railings by using several pieces of short wood and a special method called kerf cutting.
Determine the front and back of your two green-wood handrails by marking with washable marker, and then mark where you would like the wood to bend. It's important to measure carefully as the two handrails must be exact when curved.
Cut one handrail into four pieces, 2 feet long each. Depending on what kind of curve you want, going inwards or outwards, you will be making several tiny slots in the wood pieces, which will allow the wood to bend in a variety of radiuses.
Set your table saw to cut into approximately 1/4 the width of your handrail piece for starters. You can always adjust the cut if the wood doesn't seem to bend easily. Set the wood piece in place at the appropriate spot where you'd like the wood to bend. If you want a full curved bend, you need to start cutting at the center, but if you want a "hook" effect for example, you should start cutting closer to either ends of the piece. The slits will either cause the wood to bend inwards, if the slits are cut into the back, or will bend outwards if the slits are cut into the front.
Cut several slits into the wood, approximately 1/8-inch apart, making sure not to cut more than 2/3 into the wood, or else the wood can break.
Bend the wood carefully to your desired radius and then hold the bend by filling the cut slits of wood with wood glue and allow to dry for at least 4 hours.
Cut slits into another piece of wood railing the same way, or for a lighter or stronger curve, adjust as needed to get the desired curve you want. Glue the end of the second piece of wood to the end of the first with more wood glue, and then do the same with the remaining two pieces of the first handrail.
Repeat the entire process for the second handrail, cutting slots, bending the wood, and then gluing the pieces together to dry. Within a day, you should have two 8-foot wood curves ready to clamp onto finished banisters to start your own spiral staircase.