Jacob arbor is the spindle to which the chuck is fastened.
The arbor can be machined onto the end of a drill spindle or it can be a separate small part that can be removed from the drill.
Arbors are small spindle shaped shanks that maybe tapered for use in MT style sockets on drill presses, or having plain round shanks for use in machine tools.
Some cheaper drill presses require the chuck to be mounted directly to the spindle by either threading the chuck onto a threaded spindle end or to a JT taper.
All Jacob arbor are precision machined and ground for maximum performance.
