little that is really new; and to the practical reader there is no benefit in discussing those which have been used for years, unless some errors in their construction can be pointed out and removed, as in the case of the boring tool we illustrated in the earlier pages. For boring cylinders, and hollow work in general, where a bar and boring head is used, a cutter like the one shown in fig. 42 is very serviceable, but the

Fig. 42.

kind of work varies so much that one tool cannot be used continually, and the good sense and ingenuity of the workman must be the judge of what is required. Much also depends upon the feed and speed of the cutter, or the work, and unless these are well regulated, either the job is much longer in the lathe than it should be, or else it is not properly done. These details cannot be put down positively, for it very often happens that the intelligent workman does not know himself at what speed he will run until the job is under way.

It seems hardly necessary to exclaim here against the habit of idling over work that some individuals practice. "Slow speed and fine feed,"

say these gentry, make the job last longer; they are correct, undoubtedly, but they should also remember that the trick also makes their wages shorter. Men are paid for the work they do, and he that accomplishes the most and the best, will assuredly stand highest in the estimation of his employers. Let us all-as practical men-aim to drive the machines faster; have the cutters sharper, the feed as heavy as the job will bear. Let us make American engines and American machine work our pride and boast, and create a market for it all over the globe, and as a preliminary step to renown, criticize closely every thing that promises to improve the character of the tools we work with.

ABUSES OF CHUCKS.

It sometimes occurs in the operations of a machine-shop, that the ordinary chucks fitted to lathes will not take in the work to be done, and resort is then had to wooden blocks bolted to the face-plate and turned out to any desired form. Sometimes these blocks are screwed on to the spindle itself, but in either case they cost time and money to make. It would seem, from the want of care and attention paid to these necessary ap purtenances of a machine-shop, that they were considered useless except for temporary purposes

and that the only disposition to be made of them is to leave them around on the floor, under the vice bench, or in any hole or corner that is unoccupied by any thing else. Some men find them useful to batter mandrels or arbors into work they are about to turn, to sit upon at noon-time, to build a fire with in the mornings; they find them convenient to punch sheet iron upon; in short, wooden chucks are abused in an infinite variety of ways which seem to us altogether wrong. Put them away in a safe place like any other tool. Assuming that the block will not run true after being shifted from the lathe, it can still be returned and employed again for work approximating in shape to the first job it received. The block out of which the chuck is made is always the best piece of wood to be had, and it is poor economy to cut up lumber to use, or rather abuse, in the manner set forth above. And in this connection it will not be amiss for us to protest against battering up the centres of shafts or mandrels by carelessness. No good workman needs to have any remonstrance addressed to him on this score; but bad ones are continually guilty of the practice referred to. If a workman wishes to damage his reputation in the eyes of all intelligent artisans, he will take a heavy hammer and blunderingly whack away on the delicate centre. that should be as carefully protected as the pupil of the human eye. Such a course only results in

mischief; in a well-regulated shop it is soon found out, and the individual committing this outrage on common sense should be immediately dismissed from the shop.

CHAPTER VIII.

BORING STEAM CYLINDERS AND HOLLOW WORKEXPERIMENTS WITH TOOLS NEEDED-CONSERV. ATISM AMONG MECHANICS.

To be reliable and useful, a steam cylinder, or indeed any cylinder in which a piston works, must be mathematically correct as to its diameter from end to end. They are not always so; sometimes far from it. There are several reasons which may be assigned as the cause of the irregularities, and these are the manner in which the cylinder is bolted to the carriage (when bored in a lathe), the kind of tools used in cutting away the superfluous iron, the rate of speed at which the cutters travel, the shape of them, and the degree of temperature the casting acquires while being worked. For all of these troubles there are remedies.

It is the practice in the best shops to bore the cylinders upright; take out a heavy cut at first, and bring the interior of the cylinder by successive cuts (say two), to within the thirty-second

part of an inch of the size required. The remaining portion is then removed in the last cut by a tool which is neither a round nose nor a diamond point, but a combination of the two; a moderate feed is given to this tool, and the boring head, or its equivalent, started on its journey. The theory is that the round nosed tool, with fine feed, makes a dead smooth surface; this on first thought might appear desirable, but reflection will show that it is not so. Dead smooth surfaces in steam cylinders, do not wear so well at the outset as those slightly raised or ridged; and this may be accounted for by the larger surfaces exposed and the more intimate relations of the structure of the iron, or of the faces opposed to each other. Thus: cast-iron rings in cast-iron cylinders, are apt to cut when new, unless they are very loosely packed. With the round-nosed diamond-pointed tool, the objection is that the edge of it will wear away quicker, but the cut will be clearer and freer than the legitimate round-nosed tool; it will heat the cylinder less, and we think produce better results generally.

An engineer of much experience has told us that he preferred to have cylinders bored in this manner, to having such very smooth surfaces as are commonly used, and gave as a reason for his opinion that the cylinders were insured a better and more permanent finish than when glazed over at the foundry. No rude workman need take