Machine shop economy is summed up by developing every machine to its utmost efficiency, and obtaining the maximum output from each, consistent with the requirements and nature of the work, which can only be achieved by a good system of tool work. A fenced portion of the shop should be devoted to the manufacture and storing of tools for the whole of the shop requirements, discriminating between poverty and excess, and discountenancing all waste. An attendant should be appointed to supply the wants of the men, who come provided with the necessary check from the foreman, with the various stores in his charge, all of which are booked to the recipient and again when returned, explanation having been rendered to the foreman for any detrimental effect the tool may have sustained, which is intimated by another check to the storekeeper. Taps, stocks, dies, templates, gauges, twist drills, mandrils, milling cutters, etc, are all dealt with in this manner, suitably headings being fixed in a book for the purpose, together with spaces for the workman's name, number, dates, and remarks as to condition.

What is a shop without system and organisation but simply chaos? whereas with them everything is reduced to order, every man knows what to do, when and where to do it System doe3 not require any more workmen, but it reduces the work of existing hands, and everything is done well, because each is individually responsible for the particular operations in his care; but, at the same time, this responsibility is reduced to a minimum, because every individual knows the system, and that it will be rigidly carried out. In fact, it is impossible to grapple with large concerns without it, and even small ones are, or soon would be, utter failures. It also insures that nothing is interrupted, not only in one shop, but every portion of the works, by the absence, for whatever reason, of foreman, man or apprentice; also every machine is fixed to plan, so that heavy or light work can be carried on most expeditiously, and suitable crane power or lifting tackle is found exactly where it is required.

The beneficial effect of accuracy in tool work is well and easily illustrated by a twist drill. The circumferential speed for « inch to ⅞ inch diameter is 20 to 30 feet per minute on mild steel, and a good feed is about 1/100- inch for each revolution, that is half that amount per lip for each revolution; consequently if the drill is ground with uneven lips, the whole cut comes upon one edge, and therefore shortly it is damaged, and the driller reduces the feed of downward traverse until this one edge cuts well, which is apparently, to one-half the feed; and therefore even to drill at the smallest cost, absolute accuracy is required, concentric and true throughout Each edge must be of equal length for obvious reasons, and have the same angle with the centre of the drill. Grinding lines are now dispensed with, owing to the use of mechanical grinders. The angle of clearance must be studied with a view to avoid rubbing and digging; and a test - the only one that the author is aware of - for the accurate grinding of a twist drill, is that it shall refuse to pass through the hole it has drilled by virtue of its own weight.

The speed for twist drills may be taken at about 25 feet per minute, the feed being at the rate of 100 to 120 revolutions per inch of downward traverse, and say, 100 to 120 « inch holes 3 inches deep may be drilled through wrought iron or mild steel; hut taking the whole shop through, only half this quantity may he reckoned upon before the drill requires to be re-ground. Rose bits are not entirely dispensed with, as it is found useful to keep a few for the pin holes in the motion. Two very important points respecting all tools are the cutting and clearance angles; but much has been written elsewhere - in fact, whole books of no mean dimensions - upon this edge question, including all tools with one or more cutting-edges. It may be stated that in all ordinary lathe work deep cuts and coarse feeds are first principles, one roughing and one finishing, bringing down the speed to suit the cut, rather than suit the cut to the speed, for then the greatest amount of work will be done in a given time; that is, let it be a maximum of feed rather than speed, and have the finishing a good sliding cut of greater feed than the roughing. The old regime is well described in 'Extracts from Chordal's Letters' as "the wiry, rough tapering and changing surface of thc fine feed is the standard for rough work, and these defects corrected by the file are the standard for the nicer work."

Any lengthy dissertation upon screw-cutting, gaps or stays in lathe work, does not come within the limits of this section, in fact it is not required; and the same remarks relating to the cutting edges are equally applicable. It is impossible to go through and illustrate everything in the machine shop, because of multiplicity, time and space, also it is quite unnecessary. Generally, descriptions of machines that do the work will be conspicuous only by their absence, because we are dealing with methods and suitable illustrations of advancing work most expeditiously, at a minimum cost, on those machines well known to all constant readers of The Engineer, and its well illustrated advertisements.

Milling machines now Lake pre-eminence of all tools in any shop, and the raison d'etre for the efficiency and economy of the milling cutter is now so well understood, that it would he utter waste of time on the part of the author and any of his readers to enter into a lengthy argument upon that point. Too much cannot he said, and it is almost impossible to push the utility of the universal machine too far, and the adaptation of special machines during the past ten years has been quite phenomenal. One of the first essentials is to we man the machines, and then keep the cutters in order, for success depends entirely upon the facility for production of, and re-grinding the cutters, it being an absurdity to use a cutter beyond its profitable period of service. A 3-inch cutter will do probably, on an average, from sixteen to eighteen hours' work before re-grinding, which only then takes few minutes, because, in most cases, not more than 1/100-inch removed will restore the cutting edge, providing the cutter has been fairly used; but a 10-inch cutter may run quit 100 hours, the cost for re-grinding in each case not exceeding; sixpence. It is also an axiom that a repetition of work is a necessity; consequently special machines are designed with the cutter spindles placed in various positions to suit that work. Also the emery grinder has reduced the cost of the production of cutters to a reasonable and justifiable limit.