Topic 3 of 6 · Form 5
Machining and CNC
Operations: facing, parallel turning, taper turning (compound slide, taper turning attachment, tailstock offset), drilling, boring, knurling, parting off and screw cutting.
Notes for this topic 1 file, in order
Create a free account to download PDFs.
The centre lathe
Operations: facing, parallel turning, taper turning (compound slide, taper turning attachment, tailstock offset), drilling, boring, knurling, parting off and screw cutting.
- Work holding: three-jaw self-centring chuck, four-jaw independent chuck, faceplate, between centres.
- Tool geometry: rake angle (affects cutting force and chip flow), clearance angle (prevents rubbing).
Cutting speeds
Spindle speed N = 1 000v ÷ (πD), where v is cutting speed in m/min and D is diameter in mm.
Worked example: Turn a 50 mm diameter mild steel bar with a cutting speed of 30 m/min. Find the spindle speed.
N = 1 000 × 30 ÷ (π × 50) = 191 rev/min
Harder materials and larger diameters need lower spindle speeds; carbide tools allow higher speeds than high-speed steel.
Milling, shaping and grinding
Horizontal and vertical milling; slotting and keyways; dividing heads; surface and cylindrical grinding for fine finishes.
Cutting fluids
Cool, lubricate and wash away chips; soluble oil for steel; dry cutting for cast iron.
CNC machining
Programmed with G-codes and M-codes; CAD/CAM links; advantages: accuracy, repeatability, complex shapes, reduced labour; disadvantages: cost and training.
Check yourself
- Find the spindle speed for a 20 mm bar at a cutting speed of 25 m/min.
- Which chuck is used for irregular-shaped work?
- Give one function of a cutting fluid.
Show answers
- N = 25 000 ÷ (π × 20) = 398 rev/min
- The four-jaw independent chuck.
- Any one: cools the tool and work, lubricates, flushes away swarf, improves finish.
Questions about this topic (0)
No questions about this topic yet.
Sign in or create a free account to join in.