This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
Hence, in workshops, the cutting tools generally take the form B, and the scrapers that of A. But these boring tools are not for hand use, the rigidity of the slide-rest being necessary to ensure accurate work with them. Otherwise the tools under description are suitable alike for manipulation by hand or slide-rest, the difference between the 2 forms lying, not in the cutting edges, but in the relative stoutness. Slide-rest tools are made of stouter metal than the others; in the case of a small lathe, from 5/8 in. or 3/4 in. square steel, while hand tools for the same can be made from 3/8-in. steel.
Fig. 1223 is a square nose for taking finishing cuts, and Fig. 1224 a tool for scraping. Fig. 1225 is a spring tool, also used for finishing a turned surface. Figs. 1226 and 1227 are for finishing hollows and rounded parts of work, and are either kept in different sweeps or ground to radii as wanted. These latter forms, being required only to smooth and polish, are flat on their upper surfaces, and act simply as scrapers. Graving tools are merely square pieces of steel ground slightly obliquely at the cutting end, and used in hand turning and for any metal.
Almost any tool flat on its upper surface will turn brass, and the clearance angle may vary from 20° to 30°. Fig. 1228 will cut rapidly, and will keep its edge for an immense time, and, of course, can be used bent round like Fig. 1222 for boring purposes. Yet the same tool used on iron would not cut, but would become hot immediately. Figs. 1226 and 1227 make excellent brass tools.
In turning cast iron and brass no water is used, but with wrought iron it becomes necessary to cool the cutter by allowing a constant supply of water to drip upon the tool. A water-can, with a tap regulated as required, is supported on the slide-rest, and travels along with it. In hand turning it must be moved where wanted.
The tools here mentioned have been typical forms; but, bearing the broad distinctions between the various angles in mind, it is easy to make or to alter tools just as wanted. In making tools for the slide-rest, a piece of steel is cut off longer than is necessary for immediate use, and the amount of metal in it allows for the wear of a lifetime. Often also, both ends of the steel are forged into cutting edges (Fig. 1229), and hence the workman can usually find a tool at any time, either suitable for the work in hand, or which may be rendered suitable by a little alteration.
A grindstone may be made in this fashion. (Fig. 1230.) A piece of broken grindstone, 2 in. thick, is rudely clipped round to 7 in. diameter, and a 1/2-in. hole bored through the centre with a common stone bit; 2 wooden washers a, 1/2 in. thick by 4 in, diameter, also have 1/2-in. holes bored in their centres. A 1/2-in. bolt b thrust through the whole keeps them together firmly with the stone in the centre. Intended to chuck between centres, a small drilled hole is run both into the bolt head and into the screwed end, and a V-shaped slit c is filed in the head to take the fork. Turned up in place, it is an efficient little grindstone, in readiness for use the moment it is slipped into the lathe. Its only drawback is that it makes the bed in a mess - a most serious objection in the case of a bright iron bed; in that case, rig up an intermediate spindle driven from a wheel in the crank axle, and from that turn the grindstone somewhere beyond the end of the bed.
A milling tool is necessary for screw heads : you can make one with little trouble, thus (Fig. 1231): In a piece of wrought iron, 6 in. by 3/4 in. by 1/2 in., file a slot 3/4 in. long by \ in. wide. At 1/4 in. from the same end drill 2 1/8-in. holes. Then take a short broken piece from the end of a flat file, and, after lowering the temper in the fire, grind it roughly to 3/4 in. in diameter; afterwards drilling an 1/8-in. hole through the centre of this, chuck and finish the outside true and slightly hollow. An 1/8-in. screw bolt, passed through the holes in the bar and in the wheel, retains the latter in place. Then procure what is called a " hob," or master tap, used for cutting steel dies, and running that round between centres, cut the edge of the milling wheel by pressing the latter against the revolving tap with considerable force. Hardening the wheel completes the tool.
Centre punches can be made from pieces of broken rat-tail files or from round steel rod. Common drills can be forged as wanted, or purchased. Files - flat, 1/2 round, 3-cornered, and round - will be bought as necessity arises. They will all have short handles, 4-5 in. long. Spanners are needed for the nuts of the head-stock cap and for the back centre, as also for the centres of the crank, so for one and all, as for jobs of work beside, a screw wrench having a range of about 2 in. is most convenient. Callipers inside and outside, in 2 sizes, should be purchased, or a combination of the 2 forma in one can be had at the toolshops.
The last article needed is the scribing block for marking heights and centres. A simple form can be made thus (Fig. 1232): Get a base of metal, a - say 3 in. by 2 in. by 1/2 in. Procure also a bit of iron or steel rod b, 7 in. by 7/8 in. by 1/4 in., and have a piece about 1 1/4 in. diameter welded on one end to form a base and moulding, and a 1/2-in. screw beyond, c; turn and screw this into the base, keeping it as upright as possible. Temporarily unscrew and file a slot, as shown, opening it first by drilling a string of holes with a 3/8-in. drill, then replace. A bit of 1/8-in. steel bar, drawn out at the ends to about 8 in. long, will form the scribe d. A 1/4-in. slot hole in the centre will receive the set screw, which is shown in sectional plan in Fig. 1233. a, upright; b, scribe cut through the slot; c, sliding screw; d, tightening nut, which can be round as shown or a wing nut.