After my last post on turning a sphere using the Soren Berger Sphere Calipers, I received some queries on making the live center cup that holds the sphere during the final stage of turning the sphere. Custom live center cones are easy to make and open up many possibilities for supporting the work piece on the tail stock side. I have the Jet live center that came with my Powermatic and it has 3/4 – 10 threads on it. This is the same size as the threads on the popular Oneway live center.
To make custom live center cones you will need a 3/4 – 10 tap, a 5/8 drill bit and a 3/4 – 10 bolt around 2 1/2″ long.
Mount a block of wood in a chuck, turn it round and true up the face. It is best if the wood is mounted in a face grain orientation, as if you were turning a bowl. The threads that are tapped into the wood will be stronger with the grain orientated like this. Once trued up, drill a hole around 1 1/2″ deep with the 5/8″ drill bit.
To tap the block of wood on the lathe I use the following procedure. First lock the spindle on the lathe. Then position the tap at the mouth of the drilled hole and support the other side of it using a 60 degree live center. Most taps have a hole or dimple on this end allowing you to do this. Then comes the part that requires a bit of co-ordination 🙂 Using a wrench turn the tap and as it threads into the lathe turn the wheel on the tail stock to help drive and support the tap. It is actually a lot easier than it sounds.
You will need to tap the blank deep enough that when threaded onto the live center it bottoms out and the blank makes contact with the live center. This will help to support the live center cone, in much the same way that a blank held chuck jaws is supported by the shoulders of the jaws as well as gripped by the jaws. Check that this is the case before proceeding.
With the head removed from the 3/4 – 10 bolt, mount it in the chuck with a set of pin jaws. Now would also be a great time to release the spindle lock on the lathe!
Screw the blank onto the 3/4 -10 bolt. You did remember to release the spindle lock on the lathe, didn’t you?
The blank can now be turned to whatever shape you need. This custom live center cone will be used to support a goblet while the stem of the goblet is being turned.
The image below shows the finished custom live center cone mounted and ready for use.
A variety of custom live center cones for a variety of purposes. From left to right:
- A cone to fit in the mouth of a hollow form and support it.
- A cup to support a sphere.
- A convex shape to support a goblet.
- A cylinder to support a pepper mill.