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.
A simple power hacksaw attachment that can be used in connection with this versatile machine tool is shown at Fig. 341 and its utility in the small shop where such a device does not form part of the regular equipment can be readily understood.
The attachment consists of the side bar A to which the hacksaw frame is attached, and the guide bars or supports B and C that are firmly attached to the base piece F. The bar A is worked back and forth by a connecting rod E, that is adapted to be attached to the face plate of the lathe. The small bar D is a guide piece to keep the saw frame from turning.
The device is simple to build and the materials entering into its construction are not costly; in fact the design is such that it may be easily placed on or detached from the shears of the lathe. The base plate F is composed of a cast iron slab one inch thick, eight inches wide, and about five feet long. It is possible to form the guide members B and C integral when the slab is cast if they are placed on the pattern. The slide is a flat piece of steel .375 inch thick and two inches wide, the length is about four feet, though this will vary according to the stroke.
A hole is drilled in the center of the bar for a .5-inch bolt, which is to form the crankpin for the lower end of the connecting rod E. The supports B and C may be made of one-inch square machinery steel. The support B has an end turned and threaded to suit a .75-inch tapped hole made in the cast iron base F. The support C may be attached in a similar manner or bolted to the other end of the base as shown. Each support has a .375-inch slot cut through the center, this being made just large enough to permit an easy sliding fit to exist between the slide bar and the sides of the guide members.
Fig. 341. - Simple Power Hackshaw Attachment for Lathes.
The smaller guide D is made of .375-inch by one-inch machinery steel, one end being bolted or riveted to the saw frame, allowing the other end to slide through the support B, thus eliminating any tendency of the saw frame to wabble. The connecting rod E is a strip of .375 steel about two inches wide and of a length to suit that of the saw frame, which obviously determines the permissible stroke. The connecting rod is drilled at both ends for .5-inch bolts, and is intended to be attached to the face plate of the lathe at the upper end and the slide bar A at the lower end. The upper end may be moved to some extent in the slot of the face plate, making it possible to vary the stroke within the limits allowed by the slot and the size of the attachment. The saw frame is forged of machinery steel and the blade is made tight in the usual manner, by a thumb screw at the outer end of the frame. An ordinary drill or shaper vise is clamped to the base plate, this to hold the stock that is to be cut off. The attachment is bolted to the shears of the lathe by a clamping bar under them, which is pressed into engagement by a .75-inch bolt as depicted.