Franklin Day Jones

“ The right-and left-hand roughing tools A and B are especially adapted for taking deep roughing cuts. One feeds away from the center of the table, or to the right (when held in the right-hand tool-block) and the other tool is ground to feed in the opposite direction. Ordinarily, when turning plain flat surfaces, the cut is started at the outside and the tool feeds toward the center, as at B, although it is sometimes more convenient to feed in the opposite direction, as at A, especially when there is a rim or other projecting part at the outside edge. ”

“ Very often the size of a threaded hole can be tested by using as a gage the threaded part that is to fit into it. When making such a test, the tool is, of course, moved back out of the way. It is rather difficult to cut an accurate thread in a small hole, especially when the hole is quite deep, owing to the flexibility of the tool; for this reason threads are sometimes cut slightly under size with the tool, after which a tap with its shank end held straight by the tailstock center is run through the hole. ”

“ Turret lathes and automatic turning machines are equipped with a pump and piping for supplying cooling lubricant to the tools in a continuous stream. Engine lathes used for general work, however, are rarely provided with such equipment and a lubricant, when used, is often supplied by a can mounted at the rear of the carriage, having a spout which extends above the tool. Owing to the inconvenience in using a lubricant on an engine lathe, steel, as well as cast iron, is often turned dry especially when the work is small and the cuts light and comparatively short. ”

“ If a tool having very much top slope is used for brass, there is danger of its gouging into the metal, especially if the part being turned is at all flexible. The clearance angle of a brass tool is usually about 12 or 14 degrees, which is 3 or 4 degrees greater than the clearance for steel turning tools. Most brass is easily turned, as compared with steel, and for that reason this increase in clearance is desirable, because it facilitates feeding the tool into the metal, especially when the carriage and cross-slide movements are being controlled by hand as when turning irregular shapes. ”

“ The coarse finishing feed is not always practicable, especially if the boring machine is in poor condition, owing to the chattering of the tool, which results in a rough surface. The last or finishing cut should invariably be a continuous one, for if the machine is stopped before the cut is completed, there will be a ridge in the bore at the point where the tool temporarily left off cutting. ”

“ The advantage of using a piece of wire for testing, instead of a rigid tool, is that the wire, owing to its flexibility, will simply be bent backward if it is moved too close to a surface which is considerably out of true. The upper surface of a casting can be tested for parallelism with the table by using this same wire gage, or by comparing the surface, as the table is revolved slowly, with a tool held in the toolpost. ”

“ Selecting Type of Turning Machine.—The variety of machine tools now in use is very extensive, and as different types can often be employed for the same kind of work, the selection of the best and most efficient machine is often a rather difficult problem. To illustrate, there are many different types and designs of turning machines, such as the ordinary engine lathe, the hand-operated turret lathe, the semi-automatic turning machine, and the fully automatic type, which, after it is “set up” and started, is entirely independent. ”

“ The amount of feed per revolution of the work, however, should always be less than the width w of the cutting edge. Very often broad tools cannot be used for finishing cuts, especially when turning steel, because their greater contact causes chattering and results in a rough surface. An old and worn lathe is more liable to chatter than one that is heavy and well-built, and as the diameter of the work also makes a difference, a broad tool cannot always be used for finishing, even though, theoretically, it would be preferable. ”

“ Cast iron is usually turned dry or without a cutting lubricant. Experiments, however, made to determine the effect of applying a heavy stream of cooling water to a tool turning cast iron, showed the following results: Cutting speed without water, 47 feet per minute; cutting speed with a heavy stream of water, nearly 54 feet per minute; increase in speed, 15 per cent. The dirt caused by mixing the fine cast-iron turnings with a cutting lubricant is an objectionable feature which, in the opinion of many, more than offsets the increase in cutting speed that might be obtained. ”

“ When grinding a flat surface, to avoid burning, the tool should frequently be withdrawn from the stone so that the cooling water (a copious supply of which should be provided) can reach the surface being ground. A moderate pressure should also be applied, as it is better to spend an extra minute or two in grinding than to ruin the tool by burning, in an attempt to sharpen it quickly. Of course, what has been said about burning applies more particularly to carbon steel, but even self-hardening steels are not improved by being over-heated at the stone. ”

“ The horizontal boring, drilling and milling machine is very efficient for certain classes of work because it enables all the machining operations on some parts to be completed at one setting. To illustrate, a casting which requires drilling, boring and milling at different places, can often be finished without disturbing its position on the platen after it is clamped in place. Frequently a comparatively small surface needs to be milled after a part has been bored. ”

“ Sometimes the work speed cannot be as high as the tool will permit, because of the chattering that often results when the lathe is old and not massive enough to absorb the vibrations, or when there is unnecessary play in the working parts. The shape of the tool used also affects the work speed, and as there are so many things to be considered, the proper cutting speed is best determined by experiment. ”

“ Ordinarily coarser feeds and a greater depth of cut can be used for cast iron than for soft steel, because cast iron offers less resistance to turning, but in any case, with a given depth of cut, metal can be removed more quickly by using a coarse feed and the necessary slower speed, than by using a fine feed and the higher speed which is possible when the feed is reduced. ”

“ A method which makes it unnecessary to loosen the regular center, or to use a special one, is to provide clearance for the tool-point by grinding it to an angle of approximately forty-five degrees, as shown at C. If the tool is not set too high, it can then be fed right up to the lathe center and the end squared without difficulty. As for the special center A, the use of special tools and appliances should always be avoided unless they effect a saving in time or their use makes it possible to accomplish the same end with less work. ”

“ When a reamer is used in the lathe, the outer end is supported by the tailstock center and should have a deep center-hole. The lathe is run very slowly for reaming and the reamer is fed into the work by feeding out the tailstock spindle. The reamer can be kept from revolving, either by attaching a heavy dog to the end or, if the end is squared, by the use of a wrench long enough to rest against the lathe carriage. A common method is to clamp a dog to the reamer shank, and then place the tool-rest beneath it to prevent rotation. ”

“ To illustrate, if the main tool slide were to feed vertically and not horizontally, it might be advisable to lock the saddle to the cross-rail, while taking the vertical cut.
The vertical slide can be set at an angle for taper turning, and the turret is accurately located over the center of the table for boring or reaming, by a positive center stop. The machine is provided with a brake for stopping the work table quickly, which is operated by lifting the shaft of pilot-wheel A. The side-and cross-rails are a unit and are adjusted together to accommodate work of different heights. ”

“ The small and medium sizes will swing work varying from about 30 inches to 6 or 7 feet in diameter, whereas large machines, such as are used for turning very large flywheels, sheaves, etc., have a swing of 16 or 20 feet, and larger sizes are used in some shops. The size of a vertical mill, like any other machine tool, should be somewhat in proportion to the size of the work for which it is intended, as a very large machine is unwieldy, and, therefore, inefficient for machining comparatively small parts. ”

“ For example, the boring and reaming operation could be performed much faster in a turret lathe, which is a type designed for just such work, but a turret lathe cannot be used for as great a variety of turning operations as a lathe of the regular type. There are also many other classes of work that can be turned more quickly in special types of machines, but as more or less time is required for arranging these special machines and often special tools have to be made, the ordinary lathe is frequently indispensable when only a few parts are needed ”

“ Ordinarily, the hand adjustment is used for quickly moving the carriage when the tools are not cutting, although sometimes the hand feed is preferable to a power feed when the tools are at work, especially if the cuts are short. After a turret tool has finished its cut, the turnstile is used to return the slide to the starting point, and at the end of this backward movement the turret is automatically indexed or turned one-sixth of a revolution, thus bringing the next tool into the working position. ”

“ Some machinists, when cutting a double thread, simply remove the work from the lathe and turn it one-half a revolution by placing the tail of the driving dog in the opposite slot of the faceplate. This is a very simple method, but if the slots are not directly opposite or 180 degrees apart, the last thread will not be central with the first. Another and better method is to disengage the idler gear from the gear on the stud, turn the spindle and work one-half, or one-third, of a revolution, as the case might be, and then connect the gears. ”

“ A short space is first turned by hand feeding, as at D, Fig. 7, and when the calipers show that the diameter is slightly greater than the finished size (to allow for a light finishing [11] cut, either in the lathe or grinding machine) the power feed for the carriage is engaged; the tool then moves along the work, reducing it as at E. Evidently, if the movement is along a line b—b, parallel with the axis a—a, the diameter d will be the same at all points, and a true cylindrical piece will be turned. ”

“ The end of a brass tool is sometimes ground with a straight cutting edge for turning large rigid work, such as brass pump linings, etc., so that a coarse feed can be used without leaving a rough surface. The tools at N and O are for boring or finishing drilled or cored holes. Two sizes are shown, which are intended for small and large holes, respectively.
The different tools referred to in the foregoing might be called the standard types because they are the ones generally used, and as Fig. 2 indicates, they make it possible to turn an almost [58] endless variety of forms. ”