“Chucking” means gripping the wood on the lathe so it is held securely while the lathe spins the wood. These methods range from a spur drive to a four-jaw chuck. Let’s go in order.
There are several methods of holding the wood on the lathe, the most basic of which is a spur drive. If you bought a lathe, you very likely got a spur drive with it. That is the piece with the Morse taper on the back end, a point in the middle of the fat end, and four relatively sharp vanes sticking out from the face of the fat end and surrounding the point.
Let me comment for a moment about the Morse taper. Inside the threaded drive on the headstock is a hole which goes through the entire headstock. That hole is tapered to smaller as it goes in. When you put a corresponding tapered piece in the end, such as that spur drive, it mates with the taper in the drive and will not allow the spur drive to be pushed farther in no matter how much pressure you put on the piece with the tailstock wheel. But you must take care of it. All the Morse tapers at the drive end of the lathes with which I am familiar are #2 Morse tapers. Morse tapers come in sizes from a #0 to a #7, which is more than 3” across! The ones you will likely see are #2 and #3. Keep ‘em clean. Woodcraft and other sources sell a hard rubber reamer and you should have one so that you can clean the taper out occasionally to ensure a good mating. Don’t use grease, oil, WD-40, or any other lubricant on this. If you notice a burr on the taper of the tool you intend to insert, carefully file it off smoothly before you insert it or you could damage the interior of the tapered hole. Most lathes have the #2 Morse taper on the drive side and some have a #3 Morse taper on the tailstock side.
So, back to the spur drive. These are most often used for spindle turning but may also be used for other jobs as well. Center the spur drive on your piece, bring up the tailstock with a live center (also known as a bearing center) to the other end, and then tighten up the tailstock end so the spurs bite into the left side of your wood.
There is also something called a “safe drive” and is a good tool to have in your kit. The safe drive is sort of like a spur drive and is used the same way but doesn’t have the spurs. Instead, around the point is a smooth ring of steel which will bite into the end of your spindle blank with enough force to drive it but it you get a bad catch, instead of tearing out a chunk of wood, the spindle will just stop in place while that safe drive continues to spin in the end of it. These are really only used for spindle work but can save you having to start over again if you get a bad catch while making that table leg for your neighbor. Spur drives come in different sizes and styles for different applications.
Moving up the chucking hierarchy, next is the collet chuck. This is a device which goes into that Morse taper in the drive and holds a piece by tightening a collar around flexible arms inside the chuck. When you are done, you remove the piece by loosening the collar.
Next is the screw drive. Essentially, a screw drive is just that, a screw of some kind which is screwed into a pre-drilled hole in the wood. As the wood is screwed onto the screw drive, it indexes up against the face of the chuck which provides stability to the piece. When you buy a four-jaw chuck, which we’ll discuss in a moment, you get a spur drive with it. Grip the base of the screw in the center of the standard size jaws and tighten it well. When you screw on the wood, it will index against the top edge of all four jaws and be quite stable. There are also dedicated screw chucks such as the Jerry Glaser Screw Chuck, an expensive but absolutely outstanding piece of equipment. See Alan Lacer’s web site for a picture -- http://stores.alanswoodturningstore.com/-strse-47/Glaser-Screw-Chuck/Detail.bok. You will notice that the basic unit has a small face but it comes with a screw-on collar which gives the option of two more face sizes. And there is a larger collar yet which is available for the next two sizes. The thing about a screw chuck is that the piece of wood must index down on the face of the chuck in order to be stable. There is also a very small screw chuck which is available into which you place your own wood screw for turning small stuff such as drawer knobs.
And now, the four-jaw chuck. Several companies make these, with different prices. All come with their standard #2 jaws and a screw for screw-chucking as I mentioned above. The great thing about four-jaw chucks is that you can get a wide range of jaw sizes and shapes for holding nearly anything which will fit into the jaws. For example, when turning a bowl, shape the outside of the piece of wood and cut a tenon on the bottom to fit the jaws of the chuck. When you reverse the bowl, grip the tenon in the four jaws of the chuck to be able to access the inside of the bowl for hollowing. Note the shape of the jaws. Some have a straight up and down face with several sharp ridges to grip a tenon. Some are shaped to fit a dovetailed tenon. Pay attention to the shape of the inside face of your jaws so you can shape the tenon accordingly for the best grip. Many companies make these – Oneway, Nova, Vicmarc, and others. Besides gripping a tenon by tightening around it, four-jaw chucks can be used to expand into a mortise in a piece, too. For example, you could cut a mortise into the bottom of a platter, place that mortise over the jaws of the chuck, and then expand the jaws to grip the inside of the mortise. A four-jaw chuck is an expensive addition to your kit but will be one of the best buys you make in woodturning.
Finally, one more chucking method to mention is the vacuum chuck. A hollow tube is mounted into a base of some kind with soft material around the top edge of the tube. The base into which the tube is mounted has either a small face plate or a threaded nut imbedded in the base which will screw onto the drive. A vacuum pump is attached to draw vacuum through the headstock. When turned on, the vacuum may draw as much as 25psi, firmly holding whatever you have across the face of the tube. These may be used in many applications but are especially useful for finishing off the bottom of a bowl without the tailstock in the way.
This is by no means all the information available on these common methods of gripping wood for turning but is meant to pique your interest in methods which may be helpful to you. Talk to your fellow woodturners about these methods and see what works for them. You will surely find many who would be quite willing to have you visit their shops for a first-hand look at chucks and their many uses.