Woodturning

A lathe chuck is a device on the driven spindle on the head (headstock) of the machine that holds the workpiece. It grips and spins it. The chuck has "fingers" called jaws that "pinch" the workpiece between them to secure it. Chucks can be 2-, 3- , 4-jaw or more. And the chuck can be self-centering or of the independent type. The self-centering chuck will have a "scroll" of threads behind the jaws that engages them. The scroll is the screw that will close each of the jaws on the workpiece (simultaneously) with the use of a tool to tighten it. And this chuck will automatically center the workpiece in the chuck. Independent chucks will have jaws that must have a tool used on each of them independently to tighten them. And of course, the workpiece will have to be "fooled around with" until it is centered in the jaws. Workholding is a company that sells chucks and has an article with pictures. A link is provided to the site. Additional links are provided to other images. Be sure to at least look at the "6-jaw chuck taken apart" to see the scroll gear that simultaneously closes the jaws. Look closely. The shiney "circles" are not circles at all but are the gradually shaped spiral of the scroll.

The only sure method is to have the appropriate internal (female) thread eg. a nut available and to try this on the cut thread. If the fit is too tight then another cut or pass must be made on the lathe. If you are cutting both male and female threads to match then cut the female thread first and use it to check the cutting of the male thread. Submitted by Bill Lavery