This is a lathe chuck stop (also called a spider). It is positioned at the back of the jaws of a 3-jaw chuck and give a repeatable location when holding short objects. It is also useful for stopping smaller diameter stock from pushing into the through hole of the lathe. The 3D prints can be used standalone or can be used to cast metal chuck stops as I have done.

The model is designed with a slight draft for casting. This was designed for a 12x36 metal lathe with a 6" 3-jaw chuck. This model should be able to be scaled to fit smaller or larger lathes.

Note: If you have not used a chuck stop before, I suggest lightly tightening the jaws on the stock and then tap the stock with a mallet to seat the stock firmly against the stop. Then continue tightening the jaws. This will also prevent the stop from moving when the lathe is turned on.