Which of the following forces are measured directly by strain gauges or force dynamometers during metal cutting?
1. Force exerted by the tool on the chip acting normally to the tool face.
2. Horizontal cutting force exerted by the tool on the work piece.
3. Frictional resistance of the tool against the chip flow acting along the tool face.
4. Vertical force which helps in holding the tool in position.
(a) 1 and 3 (b) 2 and 4
(c) 1 and 4 (d) 2 and 3