This is so simple that I would expect everyone to know about it, but I keep running into turners struggling to center a work piece on the lathe. One common example is trying to optimize the orientation of a previously roughed-out bowl to allow a proper mounting tenon to be cut. Typically, the inside of the bowl would be pressed against a faceplate or a large chuck by a live center in the tailstock. Then the desired orientation would be obtained by tapping the bowl so that it slides on faceplate/chuck and adjusting the position of the live center as appropriate. The problem is that if you drive the center barb into the bottom of the bowl at wrong place, you can no longer slide the foot of the bowl to where it is needed. This raises two problems: First, if you loosen the live center to adjust its position, the bowl may slide on the faceplate/chuck. Second, once the barb has penetrated the work piece, it is almost impossible adjust its position by just a small amount.
A simple solution to these problems is to put a small block of sacrificial wood between the live center and the turning and let the center spur penetrate one side of this block as shown in the figure. Now, the workpiece can be mounted as described above with just enough tailstock pressure to keep everything in place. This allows each end of the bowl to be adjusted independently to optimize the position of the bowl. When adjustment is complete, I usually run a bead of CA glue on two or more sides of the block to assure that it will not move. A final point: If you expect to need to remount using the live center again after the block has been removed, first drill a small hole through the block at the center point just deep enough into the workpiece to provide a guide for the barb.
The bowl orientation application described above is only one of many applications of the technique.
A simple solution to these problems is to put a small block of sacrificial wood between the live center and the turning and let the center spur penetrate one side of this block as shown in the figure. Now, the workpiece can be mounted as described above with just enough tailstock pressure to keep everything in place. This allows each end of the bowl to be adjusted independently to optimize the position of the bowl. When adjustment is complete, I usually run a bead of CA glue on two or more sides of the block to assure that it will not move. A final point: If you expect to need to remount using the live center again after the block has been removed, first drill a small hole through the block at the center point just deep enough into the workpiece to provide a guide for the barb.
The bowl orientation application described above is only one of many applications of the technique.