Technical Guidance The Basics of Threading, Turning Edition
■ Thread Cutting Methods
Cutting Method
Features
Radial Infeed
· Most common threading technique, used mainly for small pitch threads. · Easy to change cutting conditions such as depth of cut, etc. · Long contact point has a tendency to chatter. · Chip control is difficult. · Considerable damage tends to occur on the trailing edge side.
Trailing Edge
Leading Edge
Feed Direction
Direction of Depth of Cut
Flank Infeed
N
· Effective for large-pitch threads and blemish-prone work material surfaces. · Chips evacuate from one side for good chip control. · The trailing edge side is worn, and therefore the flank is easily worn.
Modified Flank Infeed
· Effective for large-pitch threads and blemish-prone work material surfaces. · Chips evacuate from one side for good chip control. · Inhibits flank wear on trailing edge side.
Alternating Flank Infeed
· Effective for large-pitch threads and blemish-prone work material surfaces. · Wears evenly on right and left cut edges. · Since both edges are used alternately, chip control is sometimes difficult.
■ Troubleshooting for Threading Failure
Cause
Countermeasures
· Tool grade
· Select a more wear-resistant grade
Excessive Wear
· Reduce cutting speed · Use a suitable quantity and concentration of coolant · Change the number of passes · Check whether the cutting edge inclination angle is appropriate for the thread lead angle · Check whether the tool is mounted properly
· Cutting conditions
Uneven Wear on Right and Left Sides
· Tool mounting
· Change to modified flank infeed or alternating flank infeed
· Cutting conditions
Chipping
· Cutting conditions
· If built-up edge occurs, increase the cutting speed
· Biting of chips
· Supply enough coolant to the cutting edge
Breakage
· Increase the number of passes and reduce the depth of cut for each pass · Use separate tools for roughing and finishing · If blemished due to low-speed machining, increase the cutting speed · If chattering occurs, decrease the cutting speed · If the depth of cut of the final pass is too small, make it larger
· Cutting conditions
· Cutting conditions
Poor Surface Roughness
· Tool grade
· Select a more wear-resistant grade
· Inappropriate cutting edge inclination angle
· Select the correct shim to ensure relief on the side of the insert
Inappropriate Thread Shape · Tool mounting
· Check whether the tool is mounted properly
· Shallow depth of cut
· Check the depth of cut
Shallow Thread Depth
· Tool wear
· Check damage to the cutting edge
N52
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