Unibor EX03 3in arbor extension .75 Weldon shank fluid

3-inch arbor extension with .75 Weldon shank

This Unibor EX03 extension adds three inches of reach for annular cutters and twist drills that use a three-quarter inch Weldon shank. It suits machinists and maintenance crews who need extra depth without changing tooling. The hardened steel body fits standard magnetic-base drills and drill presses. It is sold new and ready for workshop use.

Installation and common issues

Slide the extension into the drill spindle and secure the cutter in the extension using the standard Weldon set-screw flat. Tighten both screws firmly before starting the cut. The most frequent problem is vibration caused by a loose set screw or a worn shank flat, which can damage the cutter and the workpiece. Keep the mating surfaces clean and inspect the flats regularly.

Practical limits of the Weldon interface

The three-quarter inch Weldon shank transmits torque through two set-screw flats, so radial run-out increases with extension length. At three inches the setup remains rigid enough for typical structural steel drilling, but heavy feed rates or hard alloys may cause chatter. The interface also limits maximum cutter diameter to the capacity of the driving machine. Coolant must reach the cutting edges through the tool’s internal passage.