Joshua Rose

“ The durability of a wheel having a fine pitch is greater for two reasons: first, because the metal nearest the cast surface of cast iron is stronger than the internal metal, and the finer pitch would have more of this surface to withstand the wear; and second, because in a wheel of a given width there would be two points, or twice the area of metal, to withstand the abrasion, it being remembered that the point of contact is a line which partly rolls and partly slides along the depth of the tooth as the wheel rotates, and that with two teeth in contact on each wheel there are two of such lines. ”

“ Since both in finishing and in polishing a piece of work the object is to obtain as true and smooth a surface as possible, the processes are to a certain extent similar, but there is this difference between the two: where polishing alone is to be done, the truth of the work or refined truth in its cylindrical form or parallelism may be made subservient to the convenience of polish. ”

“ If we now turn our attention to that class of chisel or wedge-shaped tools in which the cutting edge is not a straight line, but may be stepped or curved—as, for example, the carpenter’s plane blade—we shall find that so long as the blade stands at a right angle to the surface it is operating upon, as in Fig. 2183 at b, the shape of surface it cuts will exactly correspond to the shape of its cutting edge; but so soon as the tool is inclined to its line of motion its cutting edge will, if curved, produce a different degree of curvature on the work. ”

“ Thus in driving out a key that is fast in its seat, a quick blow is more effective than a slow one, both being assumed to have at the moment of impact an equal amount of mechanical force stored up in them. ”

“ In a milling machine the cut is carried continuously from its commencement to its end, whereas in a shaping or planing machine the tool does not usually cut during the back or return stroke. In either of these machines, therefore, the operator’s skill is required as much in measuring the work, setting the tools feeds, &c., as in shaping the tools, whereas in the milling machine all the skill required lies in the chucking and adjustment of the work to the cutter, rather than in operating the machine, which may therefore be operated by comparatively unskilled labor. ”

“ In circular saws, which usually run at high velocity, there is generated a centrifugal force that is sufficient to actually stretch the saw and make it of larger diameter. As the outer edge of the saw runs at a greater velocity than the eye it stretches most, and therefore the equality of tension throughout the saw is destroyed, the outer surface becoming loose and causing the saw to wabble as it revolves, or to run to one side if one side of the timber happens to be harder than the other, as in the case of meeting the edge of a knot. ”

“ If the Pennsylvania railroad and all its branches have adopted 3⁄32, it is folly to ask them to change it to 1⁄16 of an inch, because their own connections are large enough to make them independent of almost any other corporation, and the need of absolute uniformity in their work would cause them to stick to that particular thing. Any of you having five, six, seven, or two or three hundred engines, must make up your minds what you will do. ”

“ The most desirable cutting speeds for lathe tools varies with the rigidity with which the tool is held, the rigidity of the work, the purpose of the cut, as whether to remove metal or to produce finish and parallelism, the hardness of the metal and stoutness of the tool, the kind of metal to be cut, and the length the tool may be required to carry the cut without being reground. The more rigid the tool and the work the coarser the feed may be, and the more true and smooth the work requires to be the finer the feed. ”

“ It may be remarked that the eye of the workman is (for rough work, such as tapping or clearing holes) sufficient guide to enable the grinding of the drill true enough to partly avoid the conditions shown in these two figures (in which the errors are magnified for clearness of illustration) , because when the want of truth is less in amount than the thickness of the drill point, the centre of motion of the drill point when the drill has entered the work to its full diameter becomes neither at the point of the drill nor in the centre of its diameter, but intermediate between the two. ”

“ If it be attempted with steel tools to take a very fine cut, as, say, one of sufficient depth to reduce a diameter, say 1⁄500 inch, the tool is apt to turn an uneven surface. There appears, indeed, to be a necessity to have the cut produce sufficient strain to bring the bearing surfaces of the rest into close contact and to place a slight strain on the tool, because under very light cuts, such as named above, the tool will generally momentarily leave the cut or take a reduced cut, and subsequently an increased one. ”

“ Small work that is turned by hand may, under exceptionally expert manipulation, be made as interchangeable and more accurate in dimensions than it could be turned by tools operated in special machines. ”

“ When we adopt a standard for screw-threads, a screw-thread is adopted which has a manifest advantage. A bolt that has one screw thread can be used on any machine. But once having adopted a taper on a road, it is very difficult to make a change; and whether it is wisdom for this Association to say that thus-and-so shall be the standard taper, is a question I am unable to answer. Therefore I am unwilling to present any taper to you, and only present the facts, but will say that 1⁄16 inch is enough. The less taper you have the less material you have to cut away. ”

“ As a general rule motion in a continuous direction causes more wear under equal conditions than does a reciprocating one, because when a revolving surface commences to abrade, the particles of metal being cut are forced into and add themselves, in a great measure, to the particles performing the cutting, increasing its size and the strain of contact of the surfaces, causing them to cut deeper and deeper until at least an entire revolution has been made, when the severed particles of metal release themselves, and are for the most part forced into the grooves made by the cutting. ”

“ Tool-holding Devices.—Perhaps no part of a lathe is found in American practice with so many different forms of construction as the device for holding the cutting tool. The requirements for a lathe to be used on light work and where frequent changes in the position of the tool are necessary, are quite different from those for a lathe intended to take as heavy a cut as the lathe will properly drive, and wherein tools having the cutting edge at times standing a long way out from the tool post (as sometimes occurs in the use of boring tools) . ”

“ Strength, durability, with reference to wear from constant use, and ease of construction, would seem to be the principal requisites in any general system; for although in many cases, as, for instance, when a square thread is used, the strength of the thread and bolt are both sacrificed for the sake of securing some other advantage, yet all such have been considered as special cases, not affecting the general inquiry. With this in view, your committee decided that threads having their sides at an angle to each other must necessarily more nearly fulfil the first condition than any other form ”

“ In truing surfaces with a file a great part of the operator’s time is occupied in testing the work for parallelism, and applying it to the surface plate to test its flatness or truth, whereas in a machine of this kind both the parallelism and the truth of the work are effected by the accurate guiding of the machine table in its guideways. Furthermore, a high order of skill is essential to the production of work by filing that shall equal for parallelism and truth work that is much more easily operated upon in the machine. ”