Cause |
Solution / Countermeasures |
Lean threads because of excessive compression
（Tapping chuck's compression works.)
※ Reason for lean threads
For the compression of tapping chuck, a strong
spring is used to resist the pressure when a tap
starts to cut.
This compression should not be used for normal
tapping, but with tap adaptor with safety clutch to
prevent tap breakage.Strong compression will result
in lean threads. |
・Decrease feed rate more than tap pitch.
（85-95% of tap pitch）
・In case there is no improvement;
Feed for forward movement : 85-95％
Feed for backward movement :100％
・In case feed mechanism of spindle is master feed,
→ Use tapping chuck with compression zero.
・In case tapping chuck with compression zero is in use,
→ Check feed mechanism of the machine. |
| Sharpness of tap is low and compression
of tapping chuck works. |
・Larger chamfering for the entrance of prepard hole
・Use tap with more threads for chamfering.（2.5 threads and more）
・Weakened compression spring of tapping chuck
→ Return it to NT TOOL for repair |
| Malfunction of tension/compression |
Check if the chuck returns to its original length after pulling and
pushing bu hand |
Malfunction of clutching mechanism of tapping
chucks with auto-depth control or selfreversing
function. |
Pull the chuck and turn right by hand to check if the clutch gets disengaged
and turn left by hand to see if the clutch gets engaged.
→ Return it to NTTOOL if malfunction of the clutch is found. |
| Mischoice of tap |
・Tapping chuck with length compensation is not suitable for synchro
tap (eccentric relief).
・Use normal tap (concentric relief) which has self-advancing action. |
Cause |
Solution / Countermeasures |
| Warpage of burr has been generated at the
entrance of tap hole. |
・Return timing is premature (before tap is pulled out)
→ Revision of approach point
Guidelines ： maximum tension + 5 ?
・Too much tension
→ Increase feed rate. Must be lower than tap pitch. |
| Burr at the entrance of tap hole due to the
reaction to compression. |
Check if the compression of tapping chuck is working during
operation.
→ Decrease feed rate less than tap pitch
（85-95% of tap pitch）
→ If the problem is not fixed,
Feed for forward movement：85-95%
Feed for backward movement：100% |
| Damage at the entrance of tap hole |
・Misalignment between tap and prepared hole
→ Correction of misalignment
→ Use tapping chuck with radial float
・Chamfering at the hole entrance is too small.
→ Larger chamfering diameter |
| Damage at the entrance of tap hole |
Replacement of tap |
Cause |
Solution / Countermeasures |
| Cutting to prepared hole is difficult and compressionof tapping chuck works. |
・Check the diameter of prepared hole.
→ （Refer to table of prepared holes）
・Small chamfering and large cutting resistance
→ Larger chamfering diameter |
| Torque clutch of tap adapter (type WES)
works. |
Accumulated chips or dust at the bottom of the hole
→ Use spiral tap for evacuating chips.
（Point tap tends to push out chips.） |
Variation caused by large inertia of machine
spindle |
・Lower rotation speed（500rpm and below）
・Check the "stationary" position of the spindle (Z-axis) |
Decreased preset length of tap
・Malfunction of tapping chuck
・Malfunction of tap adaptor with length adjustment
(type WEN and WESN) |
・Tapping chuck will not return to the original length.
→ Check tension/compression of tapping chuck.
・Length adjustment screw is not back to the locking position.
→ Check that adjustment screw will not turn after adjustment
is completed. |
Cause |
Solution / Countermeasures |
| Tap hits the bottom of prepared hole and
excessive torque is applied. |
・Check NC program
・Check the clerance between tap's chamfering threads and
prepared hole.
→ If there is not enough clearance, decrease the number of
chamfering threads.
・Deepen prepared hole.
・Shallow thread depth. |
| Accumulated chip or dust at the bottom of
the hole |
Use spiral tap to evacuate chips.
（Point tap tends to push out chips forward.） |
Increased preset length of tap
・Malfunction of tapping chuck
・Chucking error of tap adaptor
・Malfunction of tap adaptor with length adjustment
(WEN and WESN) |
・Tapping chuck will not return to its original length.
→ Check tension/compression of tapping chuck.
・Tap has been pulled out of tap adaptor.
→ Check the locking mechanism of tap adaptor. (See if tap
cannot be pulled out by hand.)
・Length adjustment screw has not been returned to the locking
position (lowest position).
→ Check if adjustment screw will not turn after adjustment is
completed. |
Variation caused by large inertia of amchine
spindle |
・Lower rotation speed （500rpm and below）
・Check the stationary position of machine spindle (in Z-axis). |
