Machine tools: lathe, milling, drilling and grinding
Machine tools covers the lathe, milling machine, drilling machine and grinding machine: their main parts, operations, cutting parameters and safe setups.
Core rules
- Lathe: work is rotated and the tool fed. Turning reduces diameter, facing produces a flat end, boring enlarges an internal hole, and taper turning can use the compound slide or tailstock offset.
- Milling: the cutter rotates and the workpiece feeds. Up-milling opposes feed; down-milling improves finish but needs backlash-free feed. Use the correct cutter for face, side or slot work.
- Drilling: clamp the work, use the right point angle and coolant, and reduce feed when breaking through. Reaming needs a pre-drilled hole and low speed with high feed.
- Grinding: select wheel grade, grain and bond for the material; balance and dress the wheel; keep the guard in place and use coolant where recommended.
- Cutting speed is surface speed; feed is movement per revolution or per tooth. Always calculate before setting the machine.
Worked example
A 10 mm drill is to cut mild steel at 25 m/min. Spindle speed N = 1000S divided by pi times D = 1000 times 25 divided by 3.14 times 10, which is about 796 rpm. Set the nearest available speed below or at this value, clamp the workpiece, and use a suitable feed and coolant.
Traps
Leaving the chuck key in the lathe chuck, mounting a drill without removing the key, using a cracked grinding wheel, or changing speed while the spindle is stopped are unsafe. Wrong speed burns cutters; too much feed breaks small drills.