Holding your CNC Keyway Broach Tool
The number one rule for holding our keyway broach tool is to never, ever modify our factory rear shank. It has a flat on center-line of the insert. If the set screws for your boring bar sleeve do not line up at 12 o’clock, then get a different holder. Also, use fresh set screws in your boring bar sleeve.
The number two rule is to have a back-stop. Have the broach tool butt up against something so that it can not slide back. Whether you’re using a boring bar sleeve or an ER collet, you must have a back-stop.
If you’re using an ER Collet do not hold the collet in a VDI boring bar sleeve or similar holder. Hold the Collet directly in a Cat 40 or 50. The shank of the ER collet must be held from multiple directions off-set 90 degrees. The problem with a boring bar sleeve holding an ER collet is you are dangling our tool farther out. The VDI holder has set screws from the sides. Take a pencil and put 2 fingers on each side and run the pencil into a wall. What happens? the butt of the pencil moves up and down. And when you trig out the length of the pencil it’s moving the most at the tip. This movement will create taper in the ceiling of your keyway and possibly decrease insert life.