WORKSHOP TECHNOLOGY-Drills and drilling process
- 1. Drills and drilling process Tribhuvan University Institute of Engineering (IOE) Himalaya College of Engineering Prepared By: Er. Amrit Tiwari Lecturer Himalaya College of Engineering
- 2. • Drilling is the operation of producing circular hole in the work piece by using a rotating cutter called DRILL BIT. Drill bits materials are generally High speed steel • The machine used in drilling is called drilling machine Types of drilling machine a) Based on construction: Portable, Sensitive, Radial, up-right, Multi-spindle b)Based on Feed: Hand and Power driven
- 3. Different parts of Drilling Machine •Base •Column or Pillar •Arm •Worktable •Drill head •Spindle •Drill jigs •Chuck •Electric Motor •Pulley or gears
- 4. Sensitive upright Drilling machine • Light duty type • Drill holes upto 15mm • Can only be hand fed • Operator senses the cutting action
- 5. Upright Drilling machine • Medium and Heavy duty type • Drill holes upto 50mm • Can be hand fed or power fed • Table can move vertically and radially
- 6. Radial arm drill machine • Large and Heavy duty type • Allow operator to position the spindle directly over the work piece rather than move the work piece to the tool. • Power feed • Automatic mechanism to raise and lower radial arm
- 7. Multi spindle Drill Machine • Several station are mounted on one long table Gang Type Drill Machine • Many spindle mounted on one head • Allow many holes to be drilled simultaneously
- 8. The two most common types are 1. HSS (High Speed Steel) drill 2. Carbide- tipped drills - high production and in CNC machines Other types are Solid Carbide drill, Tin coated drills Tool Materials
- 10. Drill holding devices Drill can be directly fitted spindle and also by different attachment The different methods used for holding drill in a drill spindle are • Geared Drill Chucks: three adjustable jaws • Drill Sockets • Drill Sleeves
- 11. Types of drills • Twist drill: most common drill • Step drill: produces holes of two or more different diameters • Core drill: used to make an existing hole bigger Twist Drill Core Drill Step Drill
- 12. Drilling Operation • Drilling • Reaming • Boring • Counter boring • Countersinking • Tapping
- 13. • Drilling : Hole of certain diameter can be grounded on the body. Drilling can also be step drilling • Boring : Enlargement of the diameter of existing hold : Accuracy is not greater than the reaming operation • Reaming : Operation of finishing a drilled hole : Enlarge the hole with greater accuracy
- 14. Counter Boring : Operation of boring a second hole, a larger diameter than the first but concentric with it Counter Sinking : Operation of producing an angular surface at the end of a hole Tapping : Operation of producing thread
- 15. Cutting Speed (v):- • It’s the peripheral speed of the drill 𝑣 = 𝜋∗𝐷∗𝑁 60 where, D = diameter of the drill in m N = Speed of rotation in rpm v= Peripheral speed of drill in m/s Feed Rate (f):- • It’s the movement of drill along the axis Depth of Cut (d):- • The distance from the machined surface to the drill axis • d = D / 2
- 16. Material Removal Rate:- • It’s the volume of material removed by the drill per unit time 𝑀𝑅𝑅 = 𝜋𝐷2 4 ∗ 𝑓 ∗ 𝑁 𝑚3/𝑚𝑖𝑛 Machining Time (T) :- • It depends upon the length (L) of the hole to be drilled ,to the Speed (N) and feed (f) of the drill • t = L / f N min
- 17. Safety Precautions • Do not support the work piece by hand – use work holding device. • Use brush to clean the chip • No adjustments while the machine is operating • Ensure for the cutting tools running straight before starting the operation. • Never place tools on the drilling table
- 18. Safety Precautions • Avoid loose clothing and protect the eyes. • Ease the feed if drill breaks inside the work piece. • Lubrication is important to remove heat and friction. • Machines should be cleaned after use • Chips should be removed using brush.
- 19. Assignment Prepare summary report including the following contents (No more than 2 pages for drilling machine 1. Operating Principle 2. Different operations (can be performed by machines) 3. Discussion and conclusions (Actually what did you learn?) Deadline Next class