This section is from the book "Lathe Design, Construction And Operation, With Practical Examples Of The Lathe Work", by Oscar E. Perrigo. Also available from Amazon: Lathe Design: Construction And Operation.
First. - The tool block will not travel beyond the line of centers to permit holding small boring tools directly in the tool-post by means of any of the holders so often described which use V-block clamps and make a handy tool-holder. This distance is short 9/64 inch. It is often convenient to get beyond the centers, and to my mind, at least, an inch is a great advantage.
Second. - The stock in the tool-post is so short that it is impossible to use packing on top of the tool when doing delicate work with small tools made of wire or small straight bars, and without such packing the value of this style of tool is lost. The top of a 1/2 x 1-inch tool can be raised but 3/16 inch above the centers.
Third. - The tool-post screw is so short that the wrench runs into the clamp handle of the tail spindle, and either the rest must be removed or the wrench taken off and the screw turned with the fingers when more than a bare loosening is required. The addition of 3/4 inch to the length would avoid this difficulty and also permit the wrench to swing clear over the small face-plate.
Fourth. - The key in the lead screw for change-gears is of the Woodruff style, and falls out every time a gear is taken off. Of course this gear does not require changing often; if it did this nuisance would be unbearable and call for a properly fitted and fastened key, but as it is, the gear is changed so seldom that one forgets this key, and so it drops and must be hunted for nearly every time a gear is changed.
Fifth. - The centers are of No. 2 Morse taper, but the holes are reamed just enough larger or deeper so that no tool of that taper as fitted to the regular Morse socket can be held without a sleeve of metal or paper. This may have its advantages in preventing the too common use of such tools in the center holes, but is sometimes a great aggravation in a tool-room lathe, where every convenience would be duly appreciated.
Sixth. - The face-plate fit, so far as the screw thread is concerned, is all right, but the part chambered out next the shoulder is 1/16 inch larger than the top of thread, which makes it quite difficult to start the thread true when putting on plates or chuck, with the results that the thread often jams in starting, especially with a heavy chuck.
The turning of tapers is often accomplished by "setting over" the tail-stock to the front or rear as may be desired, so as to be out of line with the head-stock center and thereby inclining the axis of the piece to be turned with the axis of the lathe. While this is a convenient and efficient manner when the taper is one of moderate inclination, it can only be done within comparatively narrow limits.
We must therefore resort to some other method when the taper is greater than will be possible to do by setting over the tail-stock and throwing the centers so much out of line with each other as to wear them out of shape as well as to distort the form of the center-reamed holes in the ends of the piece of work.
The taper attachment was devised to meet this condition and consists essentially of fixing to the bed a bar capable of being adjusted horizontally to any desired angle, and upon which is fitted a sliding block, moving with the lathe carriage, and so attached to the tool-supporting mechanism as to cause the cutting-tool to follow in a line parallel to the inclined bar as the carriage is moved to and fro on the bed. This is accomplished by different devices by the various lathe builders, whose efforts are usually directed to three principal objects: first, to so construct the taper attachment that it may be attached to any lathe without special arrangement or preparation of the bed. It was formerly necessary in nearly every case to have planed grooves or flat surfaces at the back of the bed for this purpose whenever a lathe was to have a taper attachment fitted to, or sold with it; second, to have the attachment so designed and constructed that it may be brought into use or detached with the least possible time and trouble; and third, that the parts are so constructed as to be as absolutely rigid as possible, particularly against any strain that would tend to throw them out of the predetermined line of inclination.
Among the failures of taper attachments the most common is that of turning a taper so that the inclined line of the surface of the turned piece is curved rather than straight; sometimes convex and sometimes concave. The operator should always use special care to have the attachment perfectly rigid in all its movable parts, clamp screws tight and adjustments perfect; and that the cutting tool is set correctly at the height of the centers.
Figure 116 shows a rear view of the taper attachment as designed and constructed by the F. E. Reed Company. The inclined guide-bar A is graduated on the end so as to show the amount of taper that is being turned. This bar is secured to a plate B, which slides upon the bar which is attached to the lathe carriage. The bar A, and plate B, are secured against longitudinal movement by means of the rod D, secured to the bracket E, clamped to the bed.
Fig. 116. - Taper Attachment built by the F. E. Reed Company.
By this means there need be no special preparation of the bed of a lathe in order to use the taper attachment. The carriage must, however, be of special construction. An intermediate slide E is provided, with its rear end pivotally connected with the sliding block G, which travels upon the inclined bar A and thereby produces the variation of alignment in the travel of the cutting-tool necessary to turn a taper.
The inclined guide-bar A may be minutely adjusted by the screw H, which may be placed as shown, or in the hole shown at B, as may be desired.
It would appear that this attachment would not be of sufficient strength and rigidity to withstand the strain of heavy turning on a very severe taper, and still do accurate work.