Service Home How To Procedures ST - Hydraulic Chuck - Installation - AD0946
Last updated: 04/15/2026

ST Hydraulic Chuck - Installation

AD0946

Revision A - 04/2026

Introduction

This procedure demonstrates how to install/remove a chuck onto the following machines:

  • ST-20, ST-20L, ST-20LY, ST-20Y 
  • ST-25, ST-25L, ST-25LY, ST-25Y 
  • ST-28, ST-28L, ST-28LY, ST-28Y 
  • ST-30, ST-30L, ST-30LY, ST-30Y 
  • ST-35, ST-35L, ST-35LY, ST-35Y 

The following procedure applies to the following service kits:

  • 93-1001313 Chuck option A2-6-10" 2.5 ID

Note: Make sure to gather the correct parts for machine configuration.

Note: Pictures in this procedure are used for reference only.

Note: Make sure to clean any chips/debris that may cause issues during installation.

 

Note: You may use the installation video as a reference for installing the manual chuck. 

Hydraulic Chuck Removal

1

Push [POWER ON].

You may have to zero return machine before unclamping the chuck.

Unclamp chuck push [E-STOP] when jaws are about half way open.

The travel should be between .180" to .200"

Note: We do this so the chuck is in the correct position to remove drawnut from the drawbar.

 

2

Remove 2 of the 3 jaws on the chuck [1].

Note: Leave one jaw on so there is leverage to loosen up the 6 chuck bolts.

3

Break loose the 6 bolts holding the chuck [1].

Note: Do not remove all the way.

4

Remove final jaw and chip cover from center bore. [1]

5

Attach lifting eye bolt to the chuck.

Use crane/forklift to help remove chuck from machine.

6

Remove the 6 chuck mounting bolts [1].

7

Unscrew drawnut.

Note: The drawnut should come out easy, do not force it. If you are having trouble removing the drawnnut, reposition the height of the crane/forklift and try again.

8

Remove chuck from spindle [1].

 

9

Loosen up adaptor bolts. [1]

Note: May need to use a dead blow mallet to help loosen adaptor.

Fully remove adaptor plate. (Image 2)

Installation

1

Note: Make sure you have gathered the correct parts for the installation. There are different chucks for different RPM spindles.

Clean chuck.

Clean thread on end of drawtube.

Clean spindle face.

Clean any other surfaces or chips in and/or around assembly area.

2

Apply rust inhibitor to the spindle nose.

3

Install adaptor plate. [1]

Torque bolts to spec.

Check runout of adaptor plate NTE .0005.

4

In MDI mode, use the foot pedal to extend the drawtube. Verify that the chuck is "UNCLAMPED" with the drawtube extended.

 

5

Apply CHUCK EEZ grease to the threads of the drawtube as shown.

 

6

Apply CHUCK-EEZ grease to chuck grease ports. About 3 pumps. 

 

7

Note: Make sure to apply anti-seize grease to drawnut threads and chuck bolts.

Attach eye bolt to chuck assembly.

Use crane/forklift to lift chuck into position.

8

Install 6 mounting bolts.

Attach drawnut onto the drawtube. Do not fully install.

9

Install 1 jaw onto the chuck body.

Remove jaw when done with this step to have access to fully install drawnut.

10

Fully install draw nut.

Back draw nut off 2 1/2 turns.

Note:This helps position master jaws into correct alignment.

11

Install chip cover. [2]

Install all 3 chuck jaws. Torque to spec. [1]

 

12

Verify everything is working correctly and that the jaws are in the correct position.