FILENAMES: giromat1.jpg DESCRIPTION: This is a picture of a lathe headstock driving center. Posted by John Stevenson . John provided the following description: ----------------------------------------------------------------- There are a lot of ways to do this. Most will work OK. In industry one of the ways is to use a driving centre very similar to a pronged wood working centre. These differ in the way they operate. in wood you force the prongs into the work. In metal you use the rotation of the workpiece to force the driving teeth into the work. Look on the end of straight turned or ground bars like gearbox layshafts and you will see a series of radial lines cut into the end. Myfords make such a tool as this. It's called a Giromat. I don't know if this is a general term or just their trade name. I have posted a picture of one with the exploded drawing that comes with it on the dropbox at www.metalworking.com under the name Giromat1.jpg This file accompanies it as Giromat.txt Construction is quite simple with a heavy spring loaded centre. Around this is a loose driving dog with teeth that has four indents in the rear face. These line up with four indents in the body. These indents carry four ball bearings and a threaded collar retains all this. In use you place the part between centres and push the part onto the driving teeth with the tailstock. When you start turning as you put pressure on the work it will tens to slip, this causes the balls to climb up the indentations and force the driving dog deeper int the work. Quite simple in operation and very quick to use. One wouldn't be hard to make if someone had enough use for one.