Shaper Cutting Tools:-
Shaper cutting tools are single point tools similar to lathe tools and are frequently held in the same type of holders. Shaper tools can be ground off hand when it is necessary to change their shape to suit a particular job or to resharpen them. The little difference which a shaper tool has from a lathe, tool is because of the, fact that whereas a lathe tool has a constant, fairly uniform cutting pressure exerted on is a shaper tool is subjected to a series of sudden shocks caused by its repeated hammering into the work.
To withstand these shocks, it is necessary that the shaper tools have a larger nose radius than the lathe tools have. In many cases the back rake, angle of the shaper tool is negatively ground so that the shock of each successive cut is taken on the solid part of the tool rather than on its point. Moreover, a shaper tool is more rigid and behavior than a lathe tool.
Lathe tool has sufficient side clearance angle as it is to be continually fed sideways, whereas in a shaper tool, since the feed is given at the end of cutting stroke, a small clearance angle is necessary, to give
Lathe tool has sufficient side clearance angle as it is to be continually fed sideways, whereas in a shaper tool, since the feed is given at the end of cutting stroke, a small clearance angle is necessary, to give
relief to the side cutting edge.
Shaper tools are of two basic kinds: forged tools and tool bits. Tool bits are more widely used than forged tools because of their economy, cutting life and the ease with which they are sharpened.
Shaper tool bits may be made up of high speed steel cast alloy or cemented carbide. Since high speed steel has greater impact toughness than cast alloy or cemented carbide, tool bits made of high-speed steel are used most often.
Shaper tools may be further classified as:
(i) Roughing tools and finishing tools.
(ii) Straight and cranked neck tools.
(iii) Left hand and right hand tools.
(vi)Round nose, straight nose and flat nose tools.
(v) Slot cutting (parting off) and side recessing tools.
For rough cuts a roughing tool is used which is without back rake angle side rake angle varies from 10° to 20° (smaller angle being for hard metals and larger angle for soft metals). Side clearance varies from 5° to 6° and end clearance angle is from 3° to go. The finishing tool is normally given the front and side clearance between 2° to 4°. A back rake of about 2° is provided. A right hand tool is fed towards the operator and a left hand tool away from the operator. A round nose tool can cut down equally on both left and right sides. A square nose tool is used for roughing and finishing the sides and bottoms of grooves, keyways etc. A Swan necked tool is used for finishing cast iron as it avoids any possibility of chatter etc.
Shaper tools for cutting steel have a side rake angle of 10°-20° and a back rake angle of 2°-8°. For cutting cast iron, a side rake angle of 3°-10° and a back rake angle of 0°-3° are employed.
Working Principle of Shaping Machines
The tool held in the tool holder mounted on the ram moves forwards and backwards in a straight line over the work piece rigidly held in a vice clamped over the work table.
The work remains stationary during the forward (cutting) stroke of the tool but moves across by one cross traverse increment during the return (non cutting) stroke. The appearance of the machined surface is of a succession of closely straight line cuts.
The variety of cuts that may be made in a shaper on any of the metals used in machine work calls for tools of various shapes. Shaping, that is, cutting on a shaper, can be done to the right or to the left. It also includes roughing cuts, finishing cuts, slotting, contouring, undercutting, dovetailing, and a variety of operations. Tools are ground differently for the different cutting operations. Tools can be made from solid bars of steel or they may be made from smaller pieces of tool steel, called bills, which are ground to the desired shape and held by being clamped in a tool-holder. The large, solid tools are especially good for very heavy work because they carry away the heat from the cutting edge of the tool more rapidly. There are also tool holders using forged bits. The tool-holder with the ground bit is probably the most popular combination on a shaper
Tool holders:-
The tool holder and high-speed-steel bit have largely superseded the forged tool for shaper work. The tool bit may be ground to the shape required to accomplish the desired result for practically any operation. shows a patented tool holder (Armstrong) which, in the smaller size, is used for shaper work and, in the larger size, is very efficient for use in the planer. The construction of this tool holder permits the tool bit to be securely and rigidly held in any one of the five positions shown in b, so that horizontal, vertical, or angular cuts, either right-hand or left-hand, may be made. Another advantage of this tool holder lies in the fact that for heavy cuts the tool holder may be reversed in the tool post (and, of course, the tool bit is also reversed, Since the cutting edge is then back of the shank of the tool, the tendency of the tool to chatter or to " dig in any case the tool bit should not be allowed to project too far as these will result in unnecessary spring . Other types of tool holders are used in
