Service Home HSK - Spindle - Troubleshooting Guide - TG0073
Last updated: 10/10/2025

HSK - Spindle - Troubleshooting Guide

TG0073

Revision A - 07/2025

Introduction

The HSK-A63 option has been integrated into our previous 40T 15k inline spindle design, and this will be built on our production floor.  The HSK-A63 utilizes clamping unit style B by OTT-JAKOB. The HSK-63A spindle option is currently available on the EC-400, EC-500, VC-400/SS, UMC-1000/SS, the VM-2, VM-3, and VM-6 with optional max speeds of 12,000 or 15,000 RPM

The HSK-F63 option  is only available on the GR-712- 5AX and the GM-2-5AX. This model will have a max speed of 25,000 RPM.

The HSK-A63 option is available on the VR Series and the GM-2-5AX. This model will have a max speed of 20,000 RPM. 

The HSK-A100 option is available on the HDC-3-5AX . The HSK-A100 utilizes a collet by Rohm. This model will have a max speed of 6,000 RPM. 

     The HSK type toolholders are unlike other tool-holding solutions we use in that they are hollow, shorter, and have a steeper shank.  The acronym HSK is translated from German as hollow taper shank.  Since they are hollow and shorter, they are lighter and have the ability to perform faster tool changes. They clamp the toolholder radially and axially, contacting the toolholder with the spindle face. HSK toolholders are in general more rigid and thus reduce any noise from resonant frequencies generated within the system.  This leads to reduced chatter and an overall exemplary toolholding system.

Refer to the Tool Holder and Pull Stud - Specification reference document for the HSK63A tool holder specifications.

How it Works

        The HSK unit clamps the tool holder from the inside using gripper segments [6] that hook onto a ramp within the toolholder [10].  They press outward and thus clamp force increases from centripetal force as the spindle increases in speed. 

WARNING: Never run an HSK spindle without a toolholder.  Centripetal force will damage the gripper segments.

The TRP (tool release piston) now has an additional switch that will sense if a tool is installed to the spindle or not.  It should not allow the spindle to run without a tool. It senses an extra groove that is installed to the guide release of the spindle.

      The clamping cone [4] screws onto the drawbar.  When the drawbar unclamps the gripper segments [6] will slide back along the ramp of the clamping cone and allow a tool to be removed or inserted.  They will then slide forward and expand when the drawbar clamps. The spacer unit [8] applies a pre-load to the segments that keeps them securely installed to the spindle shaft bore they sit in.  Push-out is set by tightening or loosening the clamping cone; the locking screw [5] then locks the clamping cone into place once push-out is set. The bronze bushing [2] secures in the clamping cone via a snap ring [1]. The bushing and lip seal [3] mate with a coolant tube, if there is one, inside of the tool holder. The other seals consist of two O-rings [7] and [9]. All of these components must be sufficiently greased or clamp force could be lost and the system will wear prematurely.

 

Symptom Table

Symptom Possible Cause  Corrective Action
Coolant has filled up inside the clamping unit. TSC was run. The tool holder had a coolant tube installed.  The tool was not a TSC tool. The lip seal in the clamping cone has failed.  Replace the lip seal.  Clean and lubricate the entire clamping unit.  Inspect the small o-ring near the drawbar threads as it may also need to be replaced.
TSC was run. A coolant tube was not installed in the tool holder. Clean and lubricate the entire clamping unit.
TSC was run. A correct tool holder and tool were used. The lip seal is damaged. Replace the lip seal.  Clean and lubricate the entire clamping unit.
 The coolant tube is loose in the tool holder, or the o-ring in the coolant tube had failed. Tighten the coolant tube, replace the o-ring as needed.  Clean and lubricate the entire clamping unit.
The clamping cone locking screw is difficult to tighten or loosen while setting pushout. The locking screw is installed backwards. Remove the clamping cone.  Remove the locking screw.  Turn the locking screw around and install it onto the clamping cone.  Install the clamping cone and set pushout.
The hex in the locking screw is damaged. Remove the clamping cone.  Remove the locking screw and replace it.  Install the clamping cone and set pushout.
Clamp force is low. Clamp force gauge is not set up properly or is malfunctioning. Measure clamp force with a second gauge to rule this out.
Pushout is incorrect. Adjust clamping cone positon to obtain the correct pushout distance.
Lubrication is failing. Lubricate the clamping unit gripper fingers and clamping cone.
Clamping unit components are worn. If pushout and lubrication are correct, inspect the clamping cone and gripper fingers for wear.  Replace as needed.
Drawbar springs have failed. This is very unlikely.  Do not assume this is the cause unless all other solutions have failed.
Tool holders are hard to remove from the taper. Pushout is set too low.  (When pushout is set too low clamp force may measure very high). Adjust clamping cone position to obtain correct pushout distance.
Gripper finger are loose in pushout condition.  This will only be noticed when the drawbar is actuated without a toolholder in the taper. Clamping unit space is bound up or its spring has failed. Disassemble the clamping unit, replace the spacer.  Inspect the backup ring and large o-ring, replace as needed.
Z-axis position accuracy is inconsistent after using a probing system. The tool probe was not seated correctly. Refer to the HSK - Spindle Probe Seating section below.

Clamping Unit Replacement and Pushout Adjustment

Required Maintenance

WEEKLY:

  • Check the packing ring (lip seal) for wear
  • Check the gripper for damage, dirt, and for sufficient grease

  Note: HSK-A100 spindles should be re-greased monthly. 

  • Re-grease all edges of the clamping cone and gripper segments that contact each other
  •   Note: Do not mix grease (the spindle was assembled using METAFLUX grease: Metaflux paste 70-8508 or Metaflux spray 70.82 are acceptable). METAFLUX  product is not available from Haas Automation and can be purchased off-the-shelf
    •  If the unit is very dirty remove the clamping unit and clean thoroughly
    • Do not spray compressed air into the spindle clamping unit - it will blow out all the grease
    • Always leave a protective tool holder in the spindle that does not have through-holes to prevent contamination of the clamping unit
  • Perform approximately ten tool changes to distribute the grease evenly. 
  • Remove the tool holder from the spindle and, with a clean cloth, remove any lumps of visible grease.

6 MONTHS OR 200,000 TOOL CHANGES:

  • Measure the push-out in the unclamped position (10.5 mm +/- 0.1 mm; 0.41 in +/- .004 in)
    • Re-torque the locking screw through a clamped tool if you needed to adjust the push-out
  • Test clamp force (pull force):
    • HSK-A63: 2,835 - 4,050 lbs 
    • HSK-F63: 1,730 -  2,472  lbs
    • HSK-A100: 10,116 - 13,038 lbs
    • If clamp force is not met you may need to re-grease the clamping unit, replace broken gripper segments, or replace a worn drawbar. Troubleshoot accordingly.

WHEN DAMAGED:

  • Replace the packing ring (lip seal)
    • It's not necessary to remove the bronze bushing to replace the seal, use pliers to grip the seal

HSK - Spindle Probe Seating

When the probe is inserted into the spindle, it is possible that the probe may not be seated correctly. This will cause z-axis positioning errors for the cutting tools and may result in a scrapped part.

To avoid this problem, do the following:

  • Perform a tool change so that the probe is inserted by the double arm, not by hand.
  • After the probe has been loaded into the spindle check with a piece of paper that there is no gap between the probe and the spindle taper (see image to the right).
  • For Haas HSK A63 Spindle: If there is a small gap, refer to Set TRP Clamp Switch section in the HSK-A63 - Spindle Drawbar - Push Out procedure and adjust the clamp switch as described.

HSK tool loading

Push tool release.

Insert the tool holder into the spindle and if the face of the tool holder does not mate flush with spindle face the tool is not oriented properly. 

Remove the tool holder and rotate it 180 degrees.

Reinsert the tool holder and confirm the faces mate.

 WARNING: If a tool is inserted 180 degrees out the spindle will not rotate, however a tool change can be commanded which could cause a tool change failure or the tool to be dropped.

Special Tools Required

        All of the following tools need to be purchased in order to properly maintain and service our new HSK spindles.  These tools can be purchased off-the-shelf.  You can aquire these tools from anywhere you like, links are provided to give an example of the less common tools.  TAC Rockford and Advanced Machine Engineering Co. have good options for HSK tooling, and they also sell sturdy cases with different kit options to keep all of the tools together and protected. All tools need to be purchased in 63A and F versions or with adapters for each.  Keep tools calibrated and clean.

HSK-A63 Service Parts

ITEM HAAS P/N
1 Requires Replacement of the Complete Clampling Unit (59-1695)
2 Requires Replacement of the Complete Clampling Unit (59-1695)
3 93-3137 (LIP SEAL COOLANT TUBE HSK-A63)
4 Requires Replacement of the Complete Clampling Unit (59-1695)
5 93-3139 (LOCKING SCREW HSK-A63)
6 93-3141 (GRIPPER FINGER SET HSK-A63)
7 93-3142 (SPACER GRIPPER FINGER HSK-A63)
8 93-3143 (RING BACK UP HSK-A63)
9 93-3144 (O-RING LARGE DRAWBAR HSK-A63)
10 93-3148 (O-RING SMALL DRAWBAR HSK-A63)

H-5AX - Spindle Warm-up

Daily Warm-Up

Warning: The spindle must be warmed up using the following procedure everyday before use.

25% of Max Speed 5 minutes 

50% of Max Speed 4 minutes 

75% of Max Speed 4 minutes 

100% of Max Speed 2 minutes 

 Note: Spindle orientation can be vertical or horizontal during warm-up.

 Note: Each machine uses specific tool holders. All tools must be balanced to the maximum RPM of the machines spindle model. Tool holder type and RPM values can be found in the introduction of the HSK - Spindle - Troubleshooting Guide. Refer to the maintenance section for correct tool holder maintenance.

Caution: Never operate the spindle without a tool holder. The machine will generate Alarm 973 - FIXTURE CLAMP FAILURE.

Storage Warm-Up (4-month period)

 Warning: The spindle must be warmed up using the following procedure if it has been idle for at least 4 months.

25% of Max Speed 15 minutes 

50% of Max Speed 4 minutes 

75% of Max Speed 4 minutes 

100% of Max Speed 2 minutes 

 Note: Spindle orientation can be vertical or horizontal during warm-up.

 Note: Each machine uses specific tool holders. All tools must be balanced to the maximum RPM of the machines spindle model. Tool holder type and RPM values can be found in the introduction of the HSK - Spindle - Troubleshooting Guide. Refer to the maintenance section for correct tool holder maintenance.

 Caution: Never operate the spindle without a tool holder. The machine will generate Alarm 973 - FIXTURE CLAMP FAILURE.

Resources

Product information including ceiling speed, transferrable torque, and replacement part numbers can be found in the following documentation and on the Advanced Machine & Engineering Co. website: