Stub Holder
(Trouble shooting)

관리 : 표준담당

  Troubleshooting for Stub Holder (NT Tool)

Problem (문제점)

원인)  ⇒ Solution(대책)

Excessive play
when mounting
into spindle.
　

 ◈ In the cases of KH-A, KH series, rubber damper is deteriorated.
  ⇒ Ask NT for repair (In some cases, irrepairable.)
 ◈ In the case of KH-E series, steel ball is worn.
  ⇒ Ask NT for repair (In some cases, irrepairable.)
 ◈ In the case of KD series, finger collet taper is worn.
  ⇒ Replacement of finger collet assembly.
 ◈ In the case of KD series, finger collets are broken.
  ⇒ Replacement of finger collet assembly.
 ◈ In the case of KD series, end face to end face dimension
between spindle and finger bolt is shorter than specified dimension.
  ⇒ Check spindle dimension.
  ⇒ Make thickness of a spacer adjust to specified dimension.

Holder comes off
from spindle.

 ◈ In the case of KH/EC series, coolant pressure is higher than
specified pressure.
  ⇒ Reduce coolant pressure.
  ⇒ Check specified coolant pressure.
 ◈ In the case of KH series, spindle mounting is not proper due to
functional failure of operating sleeve.
  ⇒ When installing, push operating sleeve down to bring it into position
  for secure mounting.
  ⇒ Cleaning of operating sleeve I.D.

Coolant is leaking
 or there is
no coolant output.
　

 ◈ KH/EC is not being used. (Stub holders other than KH/EC are
not compatible with center-thru coolant.)
  ⇒ Use KH/EC.
  - For high coolant pressure KH/EC1type
  - For low coolant pressure KH/EC2 type
 ◈ Coolant pressure is higher than specified pressure.
Use coolant at a pressure equal to or lower than maximum pressure allowed.
 ◈ Collets compatible with center-thru coolant
(OH or C type collets) are not being used.
  ⇒ Use OH or C type collets.
  - OH type ... Center through  , - C type ... Collet through
 ◈ Coolant cap "O" ring is deteriorated or worn. ⇒ Replacement of O-ring.

Problem (문제점)

원인)  ⇒ Solution(대책)

Cutting tool
comes off or slips.

 ◈ Large cutting resistance to chucking force.
  ⇒ Revision of cutting conditions (Decrease cutting resistance.)
  a : Higher rotation speed or lower feed rate (Approx. 20%)
  b : Lower cutting depth
  ⇒ Shorter tool projection length
 ◈ Insufficient tightening of cap nut
  ⇒ Keep recommended torque value for tightening cap nut.
  ⇒ Use torque wrench.
 ◈ Tightening not sufficient due to cap rotary ring failure.
  ⇒ Replacement of cap nut.
 ◈ Insufficient tightening of cap nut because of increased friction
in the thread part (Tightening of collets not enough.)
  ⇒ Apply oil (grease) on the thread part after cleaning it.
 ◈ Tool tang does not fit into preset driver groove due to
  dimensional differences.
  ⇒ Check tool tang dimension and preset driver groove dimension.
  ⇒ Replacement of preset driver.

Poor accuracy.

 ◈ Spindle and holder have rattling.
  ⇒ See Problem: "Excessive play when mounting into spindle"
  in the trouble column and reduce play (clearance) to appropriate level.
 ◈ Adhered chip and dust to spindle end surface or holder end surface.
  ⇒ Cleaning of spindle end surface or holder end surface.
 ◈ Poor chucking accuracy of collet. ⇒ Replacement of collets.
 ◈ Dust seizing in collet insertion area. ⇒ Cleaning of collet insertion area.
 ◈ Scratch or dent in holder I.D. ⇒ Replacement of holder.
 ◈ Scratch or dent on collet I.D. and O.D. ⇒ Replacement of collet
 ◈ Insufficient chucking length.
  ⇒ Keep minimum insertion length. (collet ID length must be filled.)
 ◈ Poor accuracy of cutting tool. ⇒ Tool replacement
 ◈ Dust seizing in cap nut thread.  ⇒ Cleaning of thread part, applying grease.
 ◈ Malfunction of rotor ring of cap nut. (Rotor ring will not rotate smoothly.)
  ⇒ Cleaning of cap nut. (so that rotor ring will rotate smoothly.)
  ⇒ Replacement of cap nuts.

Problem (문제점)

원인)  ⇒ Solution(대책)

Chattering

 ◈ Cutting resistance is too high in comparison with chuck's rigidity
  ⇒ Revision of cutting conditions (Decrease cutting resistance.)
  a : Higher rotation speed or lower feed rate (Approx. 20%)
  b : Lower cutting depth
  ⇒ Shorter tool project
 ◈ When end-milling with series KH-E, KD-T,
The amount of cutting is a little, the end mill runs away,
and the slipping phenomenon on the grinding surface has happened.
  ⇒ Revision of cutting conditions (Increase cutting resistance.)
  a : Higher feed rate or lower rotation (Approx. 20%)
  b : Higher cutting depth
 ◈ Bending moment is too large.
  ⇒ Shorter tool projection length
 ◈ Spindle and holder have rattling.
  ⇒ See Problem: "Excessive play when mounting into spindle"
  in the trouble column and reduce play (clearance) to appropriate level.

Holder does not
come off from spindle.

 ◈ Deposition of fretting, rust and/or adhered coolant residual.
  ⇒ Cleaning of spindle and holder shank.
 ◈ In the case of KH series, operating sleeve failure.
  ⇒ Cleaning of operating sleeve I.D.