• Usually, threads are cut with the feed towards the chuck.
  • When machining left hand threads, note that clamping rigidity is lowered due the application of back turning.
  • When machining left hand threads, the lead angle is negative. Ensure an appropriate lead angle by changing the shim.

Insert Types

Infeed Methods

Threading Depth

* It is recommended to set the depth of cut of the final pass to 0.05mm─0.025mm.
Large cutting depths can cause vibration, leading to a poor surface finish.


Formulae to calculate infeed for each pass in a reduced series.


NC Programme for Modified Flank Infeed

Example) M12×1.0 5 passes modified 5°

External Threading Internal Threading
G00 Z = 5.0
X = 14.0
G92 U─4.34 Z─13.0 F1.0
G00 W─0.07
G92 U─4.64 Z─13.0 F1.0
G00 W─0.06
G92 U─4.88 Z─13.0 F1.0
G00 W─0.05
G92 U─5.08 Z─13.0 F1.0
G00 W─0.03
G92 U─5.20 Z─13.0 F1.0
G00 Z = 5.0
X = 10.0
G92 U4.34 Z─13.0 F1.0
G00 W─0.07
G92 U4.64 Z─13.0 F1.0
G00 W─0.05
G92 U4.84 Z─13.0 F1.0
G00 W─0.04
G92 U5.02 Z─13.0 F1.0
G00 W─0.03
G92 U5.14 Z─13.0 F1.0

Selecting Cutting Conditions

* Tool life and surface finish accuracy can be increased by changing the threading method from flank infeed to modified flank infeed.
* Chip control can be improved by increasing the cutting depth in the later half of passes.

Cutting Depth and the Number of Passes

Selection of the appropriate cutting depth and the right number of passes is vital for threading.

  • For most threading, use a "threading cycle program," which has originally been installed on machines, and specify "total cutting depth" and "cutting depth in the first or final pass."
  • Cutting depth and the number of passes are easy to change for the radial infeed method, thus making it easy to determine the appropriate cutting conditions.

Features and Benefits of Mitsubishi Products

  • Insert grades with high wear and plastic deformation resistance, specially produced for threading tools, ensure highly efficient cutting by enabling high-speed machining and a reduced number of passes.

Advice on Improved Threading

Increasing Tool Life

  • To prevent damage to the corner radius -Recommended method - Modified flank infeed
  • To have uniform flank wear on both sides of a cutting edge - Recommended method - Radial infeed
  • To prevent crater wear - Recommended method - Flank infeed

Preventing Chip Problems

  • Change to flank or modified infeed.
  • During radial infeed cutting, use an inverted holder and change the coolant supply to a downward direction.
  • When using the radial infeed method, set the minimum cutting depth at around 0.2mm to make the chips thicker.

To Achieve Highly Efficient Machining

  • Increase cutting speed. (Dependant on the maximum revolution and rigidity of the machine.)
  • Reduce the number of passes. (Reduce by 30-40%.)
  • A reduced number of passes can improve chip discharge because of the thicker chips generated.

Preventing Vibration

  • Change to flank or modified infeed.
  • When using radial infeed, reduce cutting depth in the later half of passes and lower the cutting speed.

Increased Surface Finish Accuracy

  • A final wiping pass should be performed at the same depth of cut as the last regular pass.
  • When using the flank infeed method, change to radial infeed only during the final pass.