Wood chucks for engineers' lathes consist of strong elm, teak, or beech discs and rings, which are of various sizes to suit various work. A wood chuck while in use is bolted to one of the disc chucks belonging to the lathe; consequently, three or four holes are made through the wood chuck to admit three or four fixing bolts. A wood chuck, in the form of a disc, is denoted by Fig. 465, which is applicable to hold very small articles, because the chuck is without a hole in the middle, and will therefore admit a small hole if necessary. Wood chucks are made to hold pieces of work in two ways, either by gripping the outside of the piece to be fixed, or by gripping its inside. If the chuck is in the form of a disc, it may be either turned until a portion of it is small enough to fit the inner surface of a ring, or a hole may be made into the middle of the chuck to fit the outer circumference of the ring. A wood chuck in the shape of a disc is indicated by Fig. 465, and another in the form of a ring is denoted by Fig. 466; Fig. 467 shows one having a stem extending from the middle, and a chuck having a conical stem suitable for holding ends of tubes of various diameters is shown by Fig. 468.