LESSON PLAN Trade: Machinist & Operator Advance Machine Tool Module/Unit: 2 Date: 15.02.2021 Time: 45 minutes Lesson No: 8 I.PREPARATION: Title: NOMENCLATURE OF DRILL 1. Objectives: At the end of the lesson the trainees will be able to: Identify the parts of twist drill & state the function of each part. Identify the various angles of twist drill and state its functions. 2. Teaching Aids: White board, Marker, Pointer, Duster, Chart, Model, Visualizer, Projector etc. 3. Introduction a. Review: In the previous lesson, we took the information about types of drill & its functions. b. Motivation: Motivate about drilling process. II.PRESENTATION: Developments / Information Points Hints Topics Parts of twist drill & Main parts of twist drill are: its function Point - is the cone shaped end, which Show models & chart does the cutting. Consist of dead center, lips or cutting edge & heel. Tang - provided on taper shank drills, for driving the drill. Flutes — are the spiral grooves on the length of drill. Helps to form cutting edges, to curl the chips & to flow the coolant. Shank — driving end of the drill, which is fitted on the machine. Taper shank is used for large diameter drills & straight shank is used for small diameter drills. Land/margin - is the narrow strip, extends to the flutes of drill. The diameter of the drill is measured across the land. Body clearance - is the part of the body, which is reduced in diameter to cut down the friction. Web - separates the flutes. Increases in thickness towards shanks. Angles of twist drill Like all cutting tool drills are provided with Show chart of and its functions certain angles for efficiency in drilling recommended drills for different materials Point/cutting angle - is the angle between the cutting edges. The angle varies according to the material. For general- purpose drill, it is 118º. Helix angle-determines the rake angle at the cutting edge. The angle varies according to the material. Three types are used as per IS Type N (13º - 16º) for normal low carbon steel. Type H (10 º - 13 º) for hard & tenacious materials. Type S (35 º - 40 º) for soft & tough materials. Rake angle - is the angle of flute. Clearance angle - is meant to prevent the friction. Help in the penetration of the cutting edge. If the angle is too much, cutting edges will be weak & if it is too small, drill will not cut. Web angle - is the angle between the chisel edge & the cutting lip. III. APPLICATION: Summary: Explain parts of twist drill, its various angles & its function in shortly. IV. TEST: 1) Name the main parts of twist drill. 2) Name the various angles of twist drill. Assignment: 1) Name the main parts of twist drill & give function of each part. 2) Name the various angles of twist drill & give function of each angle. Reference: NIMI - Machinist Trade Theory. Next Lesson: Nomenclature of Reamer Prepared by- Tarak Nath Rudra Assistant Director, NSTI Kolkata .