How to Rotary Broach

What is Rotary Broaching

Rotary broaching, also known as wobble broaching, is a unique method of cutting polygon forms into the end of a work piece using a vertical or horizontal spindle machine such as a CNC or manual lathe or mill.

The rotary broach process is idea for medical screws, shafts, gears, fasteners and many other mechanical parts.  This process can be completed in minutes in just a few steps without the need for a secondary operation such as EDM or conventional broaching.

The following polygon forms can be broached into materials such as aluminum, stainless steel, brass, titanium, iron, plastic and others using broaching tools from Polygon Solutions:

• Hexagon (hex)
• Square
• Torx
• Serration
• Keyways
• Double Square
• Double D
• Double Hexagon
• Involute
• Spline
• Spur Gear
• J500
• Rosan
• Many other special forms

Tools Needed to Rotary Broach

There are only two tools needed to successfully rotary broach:

1. Rotary Broach Tool Holder; and
2. Rotary Broach Tool

With these two inexpensive tools you will be able to broach any polygon form listed above into any material listed above.

Rotary Broaching Process

There are only a few steps needed to complete the rotary broaching process.

Lead Chamfer

There needs to be a lead chamfer added to the work piece.  Add a 90 degree chamfer slightly larger than the across the flats dimension of the rotary broach tool.

Pre-Drill Pilot Hole

Next you will need to pre-drill a pilot hole approximately 3% larger than the across the flats dimension of the broaching tool.  For example, if you are using a 1/4" Hexagon rotary broach tool then your pilot hole should be .260".  The pilot hole should be drilled twice the depth of the desired broach depth to allow for chip accumulation.

Rotary Broach Form

Now it is time to actually broach the polygon form into the work piece using the rotary broach tool and tool holder.  Speeds and feeds will vary depending upon your machine, the broach size & depth, as well as the material being broached.

As the broaching tool is fed into the pre-drilled pilot hole you will notice a chiseling or scalloping effect which is why this process is commonly known as wobble broaching.

Feed the rotary broach into the work piece until the desired depth is reach.

Remove Chips

Simply run your pre-drill pilot hole operation again to clear all the chips that have accumulated at the bottom of the work piece.  This process should be completed even if you are broaching a through hole.

Deburr Lead Chamfer

On some occasions you will notice a burr on the lead chamfer after the broaching process.  A simple run of the chamfer program will eliminate this issue and it is a good safety precaution.

Tips

• The rotary broaching process does not generate much heat so the normal amount of coolant or oil is recommended.
• When rotary broaching tougher material such as titanium, stainless steel or nickel it is recommended that you order a broaching tool made from M-42 or PM T-15.
• Coating such as Titanium Nitride, Titanium Carbo-Nitride or Titanium Aluminum-Nitride can be applied to add life to the rotary broach tool.

Support and Technical Data

If you have a question or comment regarding the rotary broaching process please visit our rotary broach forum or call 239-628-4800.

More Information

You can learn more about the rotary broaching process and the history of it at: http://en.wikipedia.org/wiki/Broaching_(metalworking)#Rotary_broaching