The second modification is more difficult to make, but equally effective. It is shown complete in [Fig. 11.] This form, arranged by the writer, has many advantages over the two last-named, and is very serviceable. A is the poppet, of the full height of the ordinary lathe heads, or a couple of inches higher. B, the slide forming the support of the piece to be bored. The form of the poppet without this attachment is shown in [Fig. 12.] If for nice work it should be made of metal and the face of it planed, but for general purposes hard wood will suffice. b, b, [Fig. 11,] are two pieces of brass forming a groove or guide in which a slide B, with dovetailed edges is fitted to work. This slide is bored, like the ordinary collar, with conical holes of different sizes, and should be made of metal and planed on back and edges. Over each hole is a mark, and this is to be brought to a similar mark on the face of the poppet. The plate is then clamped in position by a screw at the back of the poppet. One or more of such slides may be fitted at pleasure, and in case of wear or damage these are the only parts requiring to be renewed.
Figs. 12,13.
It is a good plan to arrange a socket and tee of a rest as b, c, [Fig. 13], at the back of this boring collar, especially as the position of the tool will be always the same, so that the rest may be a permanent part of the poppet. There is sometimes a difficulty with the ordinary form of boring collar in advancing the rest T sufficiently near the work (the foot of the poppet, and that of the rest preventing it, by coming in contact.) There is another modification of boring collar, forming at the same time a guide for the drill, which in slender work, where the tool is long and fine, becomes almost a matter of necessity.
This consists in making such a guide cone as mentioned and shown in [Fig. 10], B, but with a continuation containing a smaller hole for the drill, as [Fig. 14]. Both this and the other shorter cones above-mentioned may be made to screw into the poppet A, [Fig. 9], instead of being kept in place by the pins at a, a, of that figure. In that case however the hole in the poppet must be cylindrical and only used as a support for the cones themselves. In addition to the use of these boring collars already alluded to, they serve for the purpose of turning up the points of screws like those of lathe centres. These are first formed between centres with carrier chuck, the back poppet is then removed and the extreme point fitted through one of the holes of the boring collar and the marks of the centre turned off.
Fig. 14.
Another useful adjunct to the lathe is the back rest for supporting long and slender articles, which would otherwise bend under the pressure of the tool. The ordinary and simplest form is shown in [Fig. 15], and this is of general use with brush handle makers and others whose work is confined to a few sizes and shapes only. A better form is shown in [Fig. 16]. A support of wood or metal shaped like A is clamped to the lathe bed. Through the upper part the slide B passes and is wedged up so as to support the work—or the socket of a lathe rest may be arranged to take the upright part A, which must then be rounded, as shown at C.
Fig. 15.