Split Turned Legs

I am building a custom vanity cabinet.  The design features a couple pairs of split turned legs either side of each door opening.   I thought I would take the opportunity to document the process involved in creating a split turning.  Split turnings are typically used in furniture and architectural applications, as decorative elements.  The process has other applications in woodturning, including the “Lost Wood Process”.

The Merrimam-Webster dictionary definition is as follows:

 a turning (as of a baluster) split vertically and applied decoratively (as to the surface of a chest or cupboard) or used as a spindle in a chairback

 

Essentially the process involves gluing two pieces of wood together with a piece of paper sandwiched between them.  The piece is then mounted on the lathe and turned to the desired shape.  Once the turning is complete the paper joint is split using a chisel, the paper literally splits in half, yielding two identical half turnings.  A simple process, but there are a couple of important things to watch out for.

The design of the split legs I needed is fairly simple.  It is a cone, approximately 32″ long, tapering from 3″ diameter to 1″ diameter.  I started with a couple pieces of 8/4 maple, about 6 1/2″ wide and 33″ long.  One face was flattened at the jointer.  Just as with any glue joint, it is important to have the two mating surfaces flat.

The piece was then ripped in half at the table saw, yielding two pieces of 8/4 maple, each 3 1/4″ x 33″.

The only paper that I have personal experience using is the brown builders/construction paper.  It is available from the home improvement retail stores and is typically used as a paint drop or to protect new flooring from damage by subsequent trades.  It is a fairly thick paper, probably a little thicker than a brown paper bag.  I’ve read that you can use newsprint or a brown paper bag, but I don’t have any experience with that.

In order to have a successful and stress free glue I’ve learnt that you need to get everything prepared in advance.  As well as clamps, glue and spreaders, this also involves cutting the paper to size.  I also like to fold the paper over the edges of the wood so that it is easier to place in the correct position once the glue is applied.

It is very important to note that you are gluing the paper to both pieces of wood, so you need to apply the glue to both pieces of wood.  If you think of it in terms of a sandwich analogy, where the two pieces of wood are the slices of bread, and the paper is the meat in the sandwich, you need to put the mayo (glue) on both slices of bread! 🙂

Once the glue is applied to both pieces of wood, place the paper over one of the pieces …

… then place the other piece of wood on the paper, and clamp together.  I like to leave the assembly clamped overnight.  The glued up blank now measures approx. 3 1/4″ x 3 1/4″ x 32″.

After removing the clamps, I clean up the ends of the blanks at the miter saw and mark the centers of each blank.  Actually, the one center line is already determined by the glue join, I just mark the other line.  When placing the blank on the lathe it is very important to position the centers accurately at the head stock and tail stock.  The center determined by the glue line is actually more important than the other center line.  If the glue line is not placed directly on center, then the two pieces once split will not be identical.

I like to use a steb or safety center at the head stock.  This enables me to turn a bit more aggressively with out worrying about damaging the piece if I get a catch.

At the tail stock I use a cup live center.  It is VERY important to use a cup center at the tail stock.  If you use a cone center then you will split the two pieces apart as you tighten up the tail stock.

The turning on this design was not very complicated.  As I mentioned before, it was a straight taper from 3″ diameter to 1″ diameter.  However, it can be challenging to achieve a perfectly straight taper.   In order to determine some guide points I drew out the leg design life size on a piece of construction paper.  I was now able to use this drawing to determine the diameter of the finished leg at five intermediate points evenly spaced along the leg.

Once the piece was turned round, I marked the points along the leg …

… and using a parting tool and a pair of calipers, established the correct diameter at each of those points.

 

Use a spindle roughing gouge I then turned the leg just a bit bigger than the final diameters.

The final diameter and taper was established using a 1 1/4″ skew chisel.

In order to further smooth and straighten the taper I use the following trick.  First, with the lathe running slowly, I draw a pencil spiral down the length of the leg.

I then attach a piece of 120 grit sandpaper to a piece of plywood with some spray adhesive.  I run this up and down the leg as it is turning slowly.

Wherever the pencil marks are sanding off indicates a high point.  So I am then able to refine those high spots with the skew.

The piece is now sanded smooth.

The moment of truth arrives!  Time to split the turning.  This is done by placing a sharp chisel directly on the paper glue joint and gently driving it into the joint with a hammer.

It is a little slow to start …

… but once the split is started the two pieces separate very easily.  Actually, it is always a bit disconcerting as to how easily they come apart, considering that a short while ago they were spinning rapidly on the lathe!

A couple images of the pair of split turned legs.  The paper still needs to be removed.  This can be done with sandpaper, although depending on the size of the piece I will often make a shallow pass over the jointer to remove the paper.