Spindle Cage

31889_AIR CYLINDER KIT-TMC/VMC

The spindle cage is a critical part of the unclamp mechanism, ensuring tools are properly seated and released from the spindle. The key measurement to check here is the system’s bump-out — the amount the drawtube physically pushes against the tool’s pull stud to break any stiction or taper-lock. A typical bump-out should measure 0.015–0.020 inches (0.50–0.80 mm).

• At the top of the spindle cage is a threaded piston rod connected to the air cylinder (TRAK P/N: 31889).
• The reference nut (Item 004) is threaded onto the piston rod and adjusted to set the home position of the cage assembly.
• When the cage is pushed up against this nut, there should be a 5 mm “unclamp gap” between the bottom of the cage and the top of the spindle unclamp plate.
• Use a 5 mm Allen wrench, drill bit, or gage pin to set this distance.
• After setting the reference gap, rotate the cage slightly to fine-tune the bump-out.
• Hold a tool in the spindle and press the green button — you should see the tool push down slightly, even while resisting it. This confirms bump-out is occurring.
• If the bump-out is insufficient or too much, adjust accordingly before locking the cage.

Below is the 31889 assembly drawing and cross-section view of the top portion of the cage assembly. The cross section is showing the closeup details of the self-aligning connection of the cage assembly’s top plate, to the threaded piston rod of the unclamp cylinder.

• The cage’s top plate has oversized holes (highlighted in yellow in the cross-section) for the 4 locking screws.
• These holes allow the cage to self-align with the spindle unclamp plate when it contacts it.
• After installing, lightly push/pull the cage side-to-side — it should move slightly and return to center.

• Once the bump-out is dialed in, apply Loctite 243 (blue) to the 4 locking screws (Item 007).
• Screws can have light oil residue but must not be dripping — excess oil will prevent the Loctite from curing properly.
• Torque each M5-0.8 x 30 screw to 7.0 Nm (5.2 ft-lb) to lock the cage onto the piston rod.
• The cage should no longer rotate on the threads once secured.

• If the 2 or 4 screws at the top of the spindle cage come loose (especially on older machines), it can cause:
• The tool to stay stuck in the spindle, delaying release.
• The ATC arm to forcefully pull on the tool, creating a loud, aggressive sound.
• Always check these screws for tightness and Loctite during any spindle cage or tool change issues.