EFFECTS OF CUTTING CONDITIONS

Ideal conditions for cutting are short cutting time, long tool life, and high cutting accuracy. In order to obtain these conditions, selection of efficient cutting conditions and tools, based on work material, hardness, shape and machine capability is necessary.

CUTTING SPEED

Cutting speed effects tool life greatly. Increasing cutting speed increases cutting temperature and results in shortening tool life. Cutting speed varies depending on the type and hardness of the work material. Selecting a tool grade suitable for the cutting speed is necessary.

Effects of Cutting Speed

  1. Increasing cutting speed by 20% decreases tool life to 1/2. Increasing cutting speed by 50% decreases tool life to 1/5.
  2. Cutting at low cutting speed (65―130 SFM) tends to cause chattering. Thus, tool life is shortened.

FEED

In cutting with a general holder, feed is the distance a holder moves per work material revolution. In milling, feed is the distance a machine table moves per cutter revolution divided by number of inserts. Thus, it is indicated as feed per tooth. Feed rate relates to finished surface roughness.

Effects of Feed

  1. Decreasing feed rate results in flank wear and shortens tool life.
  2. Increasing feed rate increases cutting temperature and flank wear. However, effects on the tool life is minimal compared to cutting speed.
  3. Increasing feed rate improves machining efficiency.

DEPTH OF CUT

Depth of cut is determined according to the required stock removal, shape of work material, power and rigidity of the machine and tool rigidity.

Effects of Depth of Cut

  1. Changing depth of cut doesn't effect tool life greatly.
  2. Small depths of cut result in friction when cutting the hardened layer of a work material. Thus tool life is shortened.
  3. When cutting uncut or cast iron surfaces, the depth of cut needs to be increased as much as the machine power allows to avoid cutting impure hard layer with the tip of cutting edge which prevents chipping and abnormal wear.