What is drilling on lathe?

Short Answer:

Drilling on a lathe is the process of making a round hole in the center of a rotating workpiece by using a drill bit held in the tailstock. The workpiece rotates while the drill moves forward to cut the material and form a hole. This method provides accurate and straight holes, especially when the hole must be exactly in the center of the workpiece.

It is one of the most common machining operations performed on a lathe and is suitable for metals, plastics, and wood. Drilling on a lathe ensures better alignment and surface finish compared to using a separate drilling machine.

Detailed Explanation :

Drilling on Lathe

Drilling on a lathe is a machining operation used to create cylindrical holes in a rotating workpiece. In this process, the workpiece is mounted and rotated by the lathe spindle, while the drill bit, fixed in the tailstock or a drill chuck, is fed into the workpiece along its axis. This operation is mainly performed when precise and centered holes are required.

The main advantage of drilling on a lathe is the accuracy of hole alignment, as the drill automatically aligns with the center axis of the rotating workpiece. It also provides a smoother hole surface and better control of depth and diameter.

Setup for Drilling

  1. Mounting the Workpiece:
    The workpiece is properly fixed in the chuck or between centers so that it rotates perfectly on the spindle axis.
  2. Fixing the Drill Bit:
    The drill bit is held in a drill chuck, which is attached to the tailstock spindle. It must be properly tightened and aligned with the lathe axis.
  3. Tailstock Adjustment:
    The tailstock is adjusted and locked in position to bring the drill close to the rotating workpiece.
  4. Speed and Feed Selection:
    Proper spindle speed and feed rate are selected depending on the material, diameter of the drill, and required finish. High-speed steel (HSS) drills are commonly used for metal drilling.
  5. Operation:
    The lathe spindle rotates the workpiece, and the tailstock handwheel is turned to feed the drill bit into the rotating workpiece. The drill cuts the material and produces a cylindrical hole along the axis.

Working Principle

The principle of drilling on a lathe is based on relative motion between the rotating workpiece and the stationary drill. The cutting edges of the drill bit remove small chips of material as it advances into the workpiece. The frictional heat produced is removed using cutting fluids such as oil or coolant, which also improve tool life and surface finish.

The cutting speed is calculated based on the formula:
Cutting speed (m/min) = (π × D × N) / 1000,
where D is the drill diameter and N is the spindle speed in revolutions per minute (rpm).

Types of Drills Used on Lathe

  1. Twist Drill: Most common drill used for general-purpose hole making.
  2. Flat Drill: Used for larger diameter holes and rough drilling.
  3. Center Drill: Used to make a small starting hole to guide the twist drill accurately.
  4. Step Drill: Used when holes of different diameters are required in a single operation.

Precautions During Drilling

  • The drill must be sharp and properly aligned with the workpiece axis.
  • Use correct speed and feed to avoid overheating or tool breakage.
  • Apply suitable coolant to reduce friction and remove chips.
  • Withdraw the drill periodically to clear chips and prevent jamming.
  • Always ensure the tailstock and workpiece are securely fixed.

Advantages

  • Produces accurate and centered holes.
  • Reduces setup time since both turning and drilling can be done on the same machine.
  • Ensures good surface finish and dimensional accuracy.
  • Saves space and cost by avoiding the need for a separate drilling machine.

Applications

Drilling on lathe is commonly used in:

  • Making holes in shafts, rods, and bushings.
  • Preparing holes for reaming, tapping, or boring.
  • Creating central holes for further machining operations.
  • Precision component manufacturing where concentricity is essential.
Conclusion

Drilling on a lathe is an important machining process used to make precise and straight holes in the center of rotating workpieces. It combines the accuracy of a lathe with the functionality of drilling, making it a versatile operation in metalworking. With proper setup, speed, and tool maintenance, drilling on a lathe provides high-quality results efficiently and safely.