Taper Maintenance

A key component of every manufacturing operation’s Preventive Maintenance Program is the proper maintenance of all spindle mating surfaces. The average tool holder shank, whether HSK, CAT, BT, or Steep taper Face contact has a “dimension life” of about 3-5 years. This means most tool holders, regardless of brand, are usually worn beyond new “Standard ANSI or DIN” specifications.

Types of Improper tool holder wear/damage

Improper “wear” means that your tools are no longer maintaining proper spindle taper/tool shank taper contact, TIR accuracy, or even proper spindle taper alignment. All this “Wear” means your machining processes are fighting to maintain centerline and highest level of machine spindle and tool holder interface. Types of wear and causes:

Normal wear

  1. Even surface wear pattern from flange back towards retention knob end.
  2. No nicks or dents that cause high spots or low spots on taper

Improper wear and Damage:

Fretting (not rust!)

Causes:

  1. Poor drawbar force pressure
  2. Excessive radial load on cutting tool/holder assembly
  3. Spindle taper surface in poor condition or bell mouth

Resolutions:

  1. Check drawbar force to make sure in is within factory specifications
  2. Reduce radial load on application
  3. Check spindle taper and tool holder taper for “out of specification” dimensions and spindle bell mouthing

Uneven Taper Wear

Causes:

  1. Over torque of Retention Knobs
  2. Incorrect Retention knob for machine spindle
  3. Poor quality tool holder material or heat treatment and grind

Resolutions:

  1. Torque specifications for retention knob
  2. Check Drawbar Pull-Force
  3. Conduct Taper/Spindle Bluing process to see if tool taper or machine taper is correct.
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