Rotary broaching can be utilized for making small forms like hexagons and squares in soft materials like aluminum, brass and mild steel. However, when it comes to aligning multiple holes using a rotary broaching tool, the operation becomes extremely challenging. Most rotary broach holders have a free turning spindle which does not allow for alignment of the holes. The rotary broaching brake is a new mechanical solution for aligning broached forms in machined products.
Polygon Solutions Inc. designed the broaching brake to be used as an attachment to its innovative GT Series rotary broach holder. The brake mounts to the tool holder using set screws. Additional screws are included at the opening of the brake to gently tighten against the spindle. The broach is fastened into the spindle, and must make contact and be aligned at the first hole.
When the broach is engaged with the part, the brake is loose enough to allow the spindle to turn without interfering with the broaching operation. Unlike typical rotary broaching operations, turning must stop before removing the broach. When the broach is removed, the brake screws are tight enough to hold the broach's position until it makes contact with the part at the next hole.
The rotary broaching brake can be used to hold orientation for single or multiple parts. Tightening the screw to be loose enough to allow broaching, but tight enough to hold orientation requires patience and a level of experience. Some trial and error can be expected and the broach orientation will need to be checked at regular intervals. The hardware consists of standard screws and nuts that can be replaced or reordered easily.
The rotary broaching brake was used recently at the 2012 IMTS show in the Hardinge booth. Hardinge's innovative Bridgeport GX 480 APC Vertical Machining Center held multiple broach holders by Polygon Solutions. However, the block was machined with square holes which were aligned to other features on the part. The squares were machined using a broach holder with Polygon's new rotary broaching brake. The rotary broaching brake is a lightweight, low profile tool and easily fit into the VMC's tool changer. It easily slides onto the head of the holder and does not require special tools for adjustment or assembly. The brake can also be easily removed for operations where it is not required.