How to Cut a Spigot:
Philip Greenwood looks at the pros and cons of different ways to form a spigot
Cutting a spigot may sound like a simple process, but when you look more closely, there are many different ways to carry out this process. It is important to form the right size and shape for the jaws being used. If you get this shape wrong, you will not achieve the maximum grip and more importantly, you will find vibration when you start cutting. This effect will magnify the further you are away from the chuck and you could find it impossible to work on the item. This could even become dangerous if the work were to come out of the jaws. A correctly cut spigot will make life a lot easier. Spigots are used on both cross- and parallel-grain timber.
Why use a spigot?
A spigot is used a lot on spindle work. You must take into account the extra length of material needed for the spigot and parting off on spindle work. The spigot will be about 5mm wide and then you need a further 6mm waste area to part off. This means you will need an extra 11mm on top of your work length. You can still turn a spigot on the end of a piece of timber that is smaller than your jaws. If the timber is only 40mm and your jaws are meant to hold a spigot of 50mm, you can turn a spigot as in the photo (below lower). This method works but you will not achieve the same grip, so try to use tailstock support. A spigot can be used to hold a bowl while the inside is turned out.
Types of spigot
The shape of the spigot will depend on the type of jaws you are using. With dovetail jaws, the angle of the spigot needs to match the angle of the jaws as closely as possible. Furthermore of course, the spigot must be the correct diameter for the jaws to have maximum grip. If the spigot is oversized, it may not achieve the best grip. I use the jaws in the photo (see below) for most of my work. I also use parallel micro-toothed jaws (not dovetailed), which need a long and parallel spigot; these have serrated jaws that grip well when turning vases. Check with the instructions that accompany the jaws or look on the manufacturer’s website for spigot size details. The area at the bottom of the spigot needs to be cut clean to allow the jaws to sit correctly. Any ridges will cause your work to vibrate. Also make sure the side coming down to the spigot is flat or slightly concave.
Standard parting tool and callipers
One method is to use a parting tool to turn the spigot to an appropriate size. Turn a small width at first and check the size with callipers while the lathe is switched off. If the size is correct, proceed to part the full width to this diameter. You can then use a skew chisel or specifically-shaped scraper to cut the dovetail angle to match the jaws.
An alternative way is to cut the dovetail with the corner of the parting tool (see below left). I use the left corner of the tool at an angle in a levering action. Make sure the side leading down to the spigot is
flat, or has a slight slope inwards, so the jaws fit into it flat.
Skew chisel or parting tool with a skew edge
You can use a skew chisel to cut the dovetail all in one go. Use this tool flat on the toolrest, with the long point facing to the left on the spigot. Rub the bevel while lifting and pushing the skew chisel, cutting until you reach the correct size. Check frequently with callipers. This is just the same way in which you use the parting tool. Again, make sure the side is at 90° to the spigot. Alternatively, you can use a parting tool with a skew edge; just grind the edge to match the dovetail angle.
A spindle gouge could be used to cut the dovetail angle. I start with the parting tool to cut the spigot to size first. Starting at the outside of the spigot, angle the tip of the bevel of the spindle gouge to match the angle of the dovetail required. Now lift the handle so the tip of the gouge arches downwards and cuts the dovetail. You may need to take two cuts to achieve the full dovetail.