The Dynamic Art of Gear Broaching

Rotary Broaching: Getting Your Machines into Shape, By Jeff Tryles, Director of Sales, Slater Tools, Inc.

A fast and efficient machining method, rotary broaching is used for making squares, hexes, splines, serrations, keyways, Torx-type, and a range of many other internal and external polygon shapes on a work piece. If your shop uses machines such as CNC lathes and mills, Swiss-type machines and machining centers, then you already have the capability to use this efficient technique and benefit from it as an alternative to outsourcing or having to use slower and more costly methods of producing gears.

One significant advantage using rotary broaching for the manufacture of gears is that it can be performed on any CNC lathe, mill, machining center, or other turning machine. In most cases, rotary broaching can be performed at the same time as other turning operations, increasing efficiency and profitability during production without sacrificing accuracy. Unlike conventional broaching, where a series of stepped polygon forms are pushed through a hole until the desired size and form is achieved, the rotary broach cuts the full form in one pass.

Additionally, gear shapes can be machined into blind holes with rotary broaching. Using a tool holder with a built-in one-degree offset (relative to the work piece center line), a controlled wobble action is created as the broach sequentially cuts from tooth to tooth upon engagement with the work piece. The resulting benefits are reduced cutting forces, increased tool life, tight tolerances (.0005 inches), fast cycle times (1500RPM and .006 i.p.r. on average) and the ability to eliminate secondary operations on another machine.

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