Accupro 88.611.40.AP CAT40 Retention Knob 5/8-11 Thread

Product Description

The ACCUPRO 88.611.40.AP is a CAT40 retention knob designed to secure toolholders in CNC machining center spindles. It threads into the drawbar mechanism and holds the toolholder firmly during cutting operations. The 5/8-11 thread size is standard for CAT40 toolholding systems. With a high-torque Style C configuration, this knob is suited for demanding milling applications where secure toolholder engagement is critical. The overall length is 2.248 inches, the knob diameter is 0.5905 inches, and the neck diameter is 0.3937 inches. Installation is performed by CNC machinists and toolroom technicians during toolholder setup or replacement.

This retention knob is used in CAT40 spindle toolholding systems found in vertical and horizontal machining centers across job shops, production facilities, and toolroom environments. The 45-degree angle radius seat and Style C profile are common in general-purpose and high-torque milling setups. No through-coolant capability is provided, making this knob appropriate for dry or flood-coolant applications where internal coolant delivery through the retention knob is not required.

Key Features

• CAT40 taper size for standard machining center spindle compatibility
• 5/8-11 thread engages directly with the spindle drawbar
• High-torque Style C design for secure toolholder retention under heavy cutting loads
• 45-degree angle radius seat for consistent seating and repeatable toolholder positioning
• Compact neck diameter of 0.3937 inches reduces interference during toolholder changes
• No through-coolant — simplifies installation in standard flood-coolant or dry-cut setups

Compatibility

Designed as an OEM-style replacement retention knob for CAT40 toolholding systems using a 5/8-11 drawbar thread on standard CNC machining centers.

Installation Notes

Retention knobs are installed by CNC machinists or toolroom technicians using a retention knob wrench and toolholder fixture to prevent rotation during torquing. Power down and lock out the machine spindle before servicing any toolholder or retention knob. Do not overtighten — follow the toolholder manufacturer's torque specification for the CAT40 interface. Inspect the knob threads and the drawbar threads for wear or damage before installation.