Accupro 766034 St Series Retention Knob CAT40 5/8-11

Product Description

The ACCUPRO 766034 is an ST Series medium retention knob designed for CAT40 taper toolholders used in CNC machining centers. It features a 5/8-11 thread and supports through-coolant delivery via a 0.2756-inch coolant hole, making it suitable for wet-cutting operations where coolant must pass through the spindle and toolholder. With a knob diameter of 0.748 inches and an overall length of 1.882 inches, this retention knob is a direct-fit replacement component installed by CNC setup technicians and machine tool maintenance personnel. The 15-degree angle radius promotes consistent drawbar engagement and repeatable toolholder seating in the spindle.

This retention knob is used in CAT40 toolholder assemblies on vertical and horizontal CNC machining centers in job shops, production facilities, and toolroom environments. It suits applications requiring through-coolant capability, including drilling, reaming, and milling operations where directed coolant flow improves tool life and chip evacuation. The 0.55-inch pilot diameter and 0.787-inch knob-to-flange length conform to standard CAT40 interface geometry for reliable drawbar pull-stud engagement.

Key Features

• CAT40 taper size for compatibility with standard CAT40 toolholder shanks
• 5/8-11 thread for engagement with standard CNC machining center drawbars
• Through-coolant capable with a 0.2756-inch coolant hole diameter
• 15-degree angle radius promotes consistent drawbar seating and retention force
• Compact 0.748-inch knob diameter and 1.882-inch overall length for standard spindle clearance
• 0.157-inch flange thickness and 0.551-inch neck diameter for precise toolholder interface fit

Compatibility

Designed as an OEM-style replacement retention knob for CAT40 taper toolholders with a 5/8-11 drawbar thread used in standard CNC machining center spindles.

Installation Notes

Retention knobs are installed by CNC machine tool technicians. The toolholder must be fully removed from the spindle and the drawbar must be disengaged before replacing the retention knob. Use the correct torque specification published by the toolholder manufacturer — do not over-torque, as this can distort the toolholder taper and affect runout. Inspect the knob threads and toolholder bore for damage or contamination before installation.