The following are all of considerable importance in ornamental turning. Some indeed being indispensable.

• Cup Chucks
• Spring chucks
• 3-jaw and 4-jaw chucks, cement-chucks and face-plate
• Metal chucks having miniature lathe-noses, with fine threads.

The cup chucks (a) made of brass, take their name from their similarity to cups. They are of all sizes, ranging from +11 to 5" or 611 in graduated sizes. These are almost indispensable, for they hold the boxwood on which much of our work is mounted. The inside, when bought, is that of a plain taper. The boxwood is turned to a similar taper and then driven in. Often, due to shrinkage, the boxwood is insecurely held and comes adrift while the work is in progress, a most frustrating state of affairs.

To avoid this happening, the cup chucks may be given a thread, cut with the chasing apparatus to a depth of some 1/2" - the No-3 being perhaps the most suitable. A strong thread-cutting tool is necessary, used with a metal turning slide-rest if one is available.

The boxwood then has a corresponding thread cut on it, leaving a shoulder to bear against the front of the metal cup. The same cup chuck can, if required, carry several sizes of boxwood fittings as they are easily removed by unscrewing. This arrangement is very strongly advised, as nothing is more disappointing than for it to part company with the work during operations, as it is impossible to re-set it with truth in the previous position.

As the metal cup chuck is used merely for holding the wood, which in turn holds the work, it may be said that the mounting of the wood chuck on to the mandrel nose, without the intervention of the cup chuck might suffice. This may be so for many purposes, but in many cases this is inadvisable, for instance, where the work has to be removed and reset to an identical position. In this case! the wood chuck (according to the amount of force used) tends to screw farther round on the mandrel which the metal cup chuck, if properly fitted, is incapable of doing.

The cup chuck is essential for oval-turning for the same reason, as the pressure of the tool is sufficient sometimes to displace the work in progress, and the truth of one operation in relation to others may be upset. Where this class of chuck has to be made, there is no reason why it should be cup-shaped. It may, with advantage, take some other form more suited to work on the dome chuck, and equally suited for all other classes of work.

Spring chucks (b) are, with minor exceptions, made of wood, having four or six saw-cuts extending length-ways from the face to some two-thirds of the distance towards the mandral nose. The body is taper in form and is provided with a brass ring which has a corresponding internal taper. This ring, on being forced down upon the outside taper closes up the sections of the chuck which the saw-cuts have formed. The end of the chuck requires a recess to be made in it, just large enough for the work to enter. It is then made fast by pushing the ring towards the larger end. In this way work already partly turned can be held in truth and without damage.

A 3-jaw concentric metal chuck (c) with two sets of jaws is extremely useful for quickly mounting work that has to be turned. A 4-jaw independent chuck of about the same diameter (say 3") is especially useful for holding work on the oval chuck. By its use time as well as material can be saved. Hollow pieces of ivory of irregular formation can be adjusted very accurately by means of the four independent jaws, so that the largest ovals can be turned without avoidable loss or waste.

When an oval recess or (as is sometimes the case) an oval periphery has been turned, the work is removed from the 4-jaw chuck and re-mounted on a prepared wooden chuck which has had turned on it an exterior projection corresponding to the recess previously turned in the ivory. When this fitment is complete, and the work can be pressed into position on the wood chuck, the back of the ivory is glued. It is essential that no glue enters the recess, as this would make the work very difficult to remove. The glue most suited to this purpose is Le Pagels,being always ready for immediate use, and allowing the work to be taken in hand within an hour at the most of the glue being applied.

A metal face-plate is, on occasions, a useful appliance. By means of its slots and various holes, and angle-plate may be fastened so that work of square formation may be clamped. This arrangement is tolerable only in the absence of a rectilinear chuck. Incidentally a 4-jaw independent chuck used in conjunction with the rectilinear allows certain types of work to be mounted quickly. To prevent bruising by the jaw, strips of soft metal or wood may be interposed.

The cement chuck.is another useful accessory. Its form is that of a small face-plate minus slots or holes. The cement used is that made of pitch, glue and gutta percha in equal proportions, melt together in a pipkin, pour out on an oiled slab of marble or iron; when cool roll with fingers (also oiled) into sticks for future use.

Screw-nose chucks (d) are most useful for chucking small component parts of work in hand. Two or three pairs are advisable with the front noses of various sizes, say *11, +11 and +" Whitworth for preference. Whitworth taps and dies can be used in the making of the chucks and in tapping threads in the work.

{Ed. note: These are called by Holtzapffel "Double screw chucks -- lsee Vol.4 page 237, figs. 296,297,298 and 299.}