11) Which type of drilling machine is most suitable to drill in a very large and heavy work pieces?

12) What is the angle of counter sink rivet head?

13) What is the angle of beveled heads of counter sink head screws?

14) Which type fo drilling machine is best suited to drill multiple holes in a work piece in a single setting?

15) Calculate the cutting speed used for drilling a 20 mm dia meter hole in a mild steel work piece with a rpm of 399?