Woodturning Chucks
Limited only by human ingenuity over the ages

Screw chuck

A faceplate which has a single screw, fixed in position and projecting from the exact centre of the face, is known as a "screw chuck". Sometimes they are supplied as a freebie with a multi chuck but it is better if you have an independent one. Screwchucks with a pointed small screw enable quick mounting of small blocks of wood - you can just screw the block on while the screwchuck is on the lathe. Screw chucks with larger parallel threaded screws require you to drill a pilot hole first but give a superior grip.
You can make servicable screw chucks yourself out of wood on your lathe! These are handy for holding such projects as wooden fruit, toy wheels or anything which can be held by a small central hole.

Faceplate

A faceplate is really a type of chuck. It is a flat metal disc which screws onto the the spindle and grips the wood by means of wood screws passing through fixing holes in the plate. You need one for initial mounting of, for example, a bowl blank, to enable you to prepare the wood to fit chuck jaws. It has many other uses. You only need a small one for most purposes and anything bigger than 4 inch can be too big. A battery screwdriver speeds things up a lot and hardened sheet metal screws are preferable to soft steel screws.

Cupchucks and "jam-chucks"

Cupchucks appear in all the old books as they have been used for hundreds of years. For ages, there was nothing else and the name chuck was synonymous with "cupchuck". The commercial ones were cast iron with a hole, tapered or parallel, to take the wood, and threaded to fit the lathe spindle. The principle of operation was that the wood was roughly turned or pared down with knife or axe, and hammered into the hole in the "chuck" to grip the work. If the cupchuck is made from scrap wood and hollowed out to fit the workpiece it is called a "jam chuck".

Jam Chucks

Simple but effective chucks can be home made from scrap wood attached to a faceplate. The scrap wood is hollowed to just the right size for the workpiece to be driven in. Alternatively, if the workpiece has a hole, the scrap wood chuck can be shaped to a slightly tapered plug or tenon which is a drive fit into the hole. These drive fit chucks can only work with workpieces which have been already turned to a true circle.

Multi Purpose Chucks

Most turners nowadays think of a chuck as one of the modern "multi chucks" which are supposed to grip just about anything. These complex and expensive devices are very desirable - although not strictly essential. There is a bewildering variety of multi purpose chucks available. Most of them can be classified as either "collet chucks" or "scroll chucks". Collet chucks have only a limited movement in the jaws, normally about 6mm change in diameter. This means that the wood has to be accurately cut to fit into the chuck jaws. The chuck jaws or "collets" are specially shaped with a hook or dovetail section to get a positive grip on the wood. The special jaws are made to either expand into a prepared recess in the wood or they contract over a "spigot" which again has to be prepared on the end of the workpiece. Scroll chucks have the advantage of a much larger jaw movement. This makes it much easier to prepare the wood to fit, because less accuracy is needed. Scroll chucks are much more expensive to manufacture than collet chucks and a good scroll chuck with a selection of dovetail jaws can cost more than a lathe. Scroll chucks use the same mechanism as metal turning chucks and have a powerful grip. A four jaw scroll chuck can grip some wood blanks, particularly square section blanks without any preparation. The security of grip in this case is only good enough for small projects because of the small contact area but the saving in preparation time is sufficient to justify the extra cost of this type of chuck to a professional turner.
More about them here

Scroll Chucks v. Collet Chucks

If you are only turning for a hobby then the time and inconvenience of having to accurately prepare the wood to fit the chuck is of little consequence. A good multi purpose collet chuck is all you require and will give an equally strong grip to a scroll chuck.

Choosing a COLLET CHUCK

It is important to be able to grip in both directions - internally and externally. Some of the older chuck designs can only grip in one direction - or the chuck has to be dismantled and reassembled in a different form to change over from internal grip to external or vice versa.

The Masterchuck is not a collet chuck

It is actually a four jaw self centering scroll chuck. The scroll is conical. It is an example of a chuck which grips in either expansion or compression and it also offers a valuable alternative to the need to prepare the wood to fit the chuck - the chuck can be fitted with wooden jaws which are shaped to fit the job! You often need to rechuck a workpiece to finish turn the part previously held (and thus rendered inaccessible) by the chuck jaws. Home built wood jaw sets are ideal for "second op. work" as they say in engineering. Quadrants of scrap wood or plywood are screwed on to the face of the existing metal jaws. The assembly is mounted on the lathe and the wood jaws turned to shape. They can just as easily be re-shaped later for another job. The wood jaws can be as simple or elaborate as the job demands and they can grip internally or externally. If they are shaped while on the chuck they are bound to run true.

Dovetail jaws v engineering style stepped jaws

You might imagine that all that is necessary with any chuck is to push the piece of wood into the chuck jaws and tighten up. After all, metal turning chucks work that way. Alas, life is not so simple for the woodturner. Wood is a weak, soft material compared to metal and, to grip it securely, the chuck jaws must clamp over a large surface area. Engineering chucks have small jaws which touch a small area on the workpiece. This is fine for gripping metal but does not work on wood because the the jaws would crush into the material long before they generate enough friction to grip securely. Turning at the end of a cylinder held this way would wrench the wood out of the jaws. To grip properly the jaws must be shaped to fit all round the circumference. Also, for maximum grip, the chuck jaws should hook over a "dovetail" shape on the wood. This locks the wood firmly into the chuck. Woodturning chucks are therefore designed with these special "dovetail" jaws as standard. They are shaped to touch all round the workpiece.

The Masterchuck has dual purpose jaws which have dovetails shaped on both the inside and the outside gripping areas. This allows either contracting grip or expanding grip, using the same jaws. The wood must be the correct diameter to fit the curvature of the jaws and shaped with the correct angle of "dovetail".

Glue Fix Chucks

A workpiece can be glued to a chuck made from scrap wood screwed to the faceplate. When the work is finished the scrap piece can be turned away using a parting tool. There are chucks available which use hot-melt glue to fix onto the workpiece. When the work is finished the workpiece is removed by heating the chuck to re-melt the glue.

Sticky Chucks

This is a development of the above by Jack Cox. A metal disc is heated before the hot melt glue is applied. This gives a very strong joint and the wood is ready to turn as soon as the glue cools. The aluminium disc is machined to fit the chuck jaws. When the project is finished the disc is re-heated to release it, leaving a flat surface with no recess. More info on sticky chucks.

Ring Chucks

A relic from the past described by Frank Pain in his excellent book "The Practical Woodturner" 1957. He called it his "eggcup chuck". This looks like a faceplate with a thread turned on the periphery. It has a ring which screws onto the rim of the faceplate. The ring has a restricted opening to trap the wood inside it. The idea is that you turn down the wood between centres with a flange at one end. The ring is big enough to pass over the wood but the flange is trapped firmly inside the ring giving an unsurpassable rigid grip. If you have one of these you will find it really useful for small cylindrical projects like peppermills, goblets and of course eggcups. The coil grip chuck is based on a giant "eggcup chuck" and performs well in ring chuck mode for projects up to 3" diameter.