The cutting tool exerts force F on the shaft in the direction shown. Clair and was impressed by his clear description of.
Lathe bit sharpening jig and vertical shear bit. Here are shown a diamond point, a round- nose tool, a side tool, centering tool, thread- cutting tool, and cutting- off tool. We will now take up the subject of the cutting edges of some of the many varieties of lathe tools, Fig. It will be noticed that it has side rake and instead of being straight on the bottom, the line that comes in contact with the work is a little rounding. It is made from a piece of ordinary tool steel and forged on the end in the shape indicated. 4, approaches the ideal for a finishing tool, and gives the best finished surface of any that I have used on planer or shaper.
To obviate any spring the tool may be designed as in the second sketch, Fig. What many mechanics take as an indication of the spring of the tool is really due to the chatter of the planer since a rack and pinion planer will frequently chatter after it has become worn, while in a worm- driven planer the lost motion is all taken up at one end before beginning the cut and the screw action does away with the chatter. This is not so serious as appears on the face of it, as planer tools are usually so stiff that they will spring but little and any error that might occur in the roughing cut would be eliminated in the finishing cut. In the first sketch the tendency is for the tool to dig into the work in the direction of the arrow. Another reason why a planer tool tends to dig into the work is illustrated in Fig. There should be very little top rake on account of its tendency to make the tool dig into the cut but this can be compensated for by giving considerable side rake. Theoretically if the point leads by only a thousandth or two it will perform its function. The 7 degrees clearance shown in the lathe tool in the upper view, Fig. A tool must first of all be heavy enough at the back or heel to resist the horizontal cutting force, and consequently should have very little clearance. This tool is wholly wrong nor would it materially improve it to grind like the tool shown in the little sketch at the right, which goes to the other extreme, and would spring into the work. It cannot exert any force tending to lift or curl the chip. It exerts its force in a direction nearly parallel to the surface of the work and having no side rake, either, it simply does not cut, but shoves or crowds the metal forward, producing a chip made up of little splints. 1 the cutting tool is at right angles to the work and without rake. This is due mainly to the compression of the metal in the direction of the cut, and you will thus see the possibilities of saving power and strain upon the machine by giving proper cutting angles to the tools and reducing this compression to a minimum.
You have doubtless observed that if the chip be unwound from the spiral shape it assumes in leaving the tool, and projected in a straight line it is shorter than the surface from which it came. Planer tools will first come under our notice as being the simplest and requiring the least skill in setting.