The following points highlight the fifteen main parts of twist drill. The parts are: 1. Body 2. Shank 3. Dead Centre 4. Point 5. Cutting Edge 6. Lips 7. Lip Clearance 8. Margin 9. Body Clearance 10. Webs 11. Rake Angle of a Drill 12. Helix Angle 13. Point Angle 14. Chisel-Edge Angle. Part # 1. Body: It is the [...]
There is a wide variety of types and sizes of drills. Fig. 18.17 shows the various types of conventional and special purpose drills. Most twist drills are made of high speed steel with or without a carbon-steel shank joined to the body. Some drills are made of cobalt alloys and others have inserts of cemented carbides. Type # 1. Taper-Shank [...]
The drilling or boring of long, relatively small diameter holes presents special difficulties which prevent the employment of ordinary drilling methods. Spade drills were originally used for this work, but lack of accuracy, poor quality of finish, and short tool life, coupled with the slowness of the operation due to need for frequent withdrawal of the drill in order to [...]
In this article we will discuss about:- 1. Meaning of Drilling Machine 2. How to Specify a Drilling Machine 3. Operations Performed by Drilling Machine 4. Cutting Speeds and Feeds of Drilling Machine 5. Machining Time in Drilling 6. Power for Drilling 7. Drills and Drilling 8. Cutting Process in Drilling Operation 9. Drill Wear and Sharpening a Drill. Meaning [...]
To obtain best results in drilling operations, following points should be observed carefully: (i) Machine tool must be rigid enough otherwise parts may be deformed by the cutting forces generated. Drill feeding arrangement must be directionally stable. (ii) Accurately ground drill should be used so that uniform chips are produced by both cutting edges, otherwise unbalanced forces may deflect the [...]