Broaching on CNC Mill?

[tkoden]

Is it possible to use something like a rotary broach with a CNC Mill to make an internal hex?

Here is some of the background info. Normally I just make a hole and take the parts to another company to have them pull broached, but is it possible for me to use something like a rotary broach in a cnc mill? The material is usually something comparable to a 1020 steel (Martin off the shelf gears) that I have to machine and then they get broached. The parts have between a .375 - .625 flat to flat hex that goes through about .375 thick material (thru hole not blind). I would be doing this on a VF1. Are there any other cost effective ways to do this without spending large amounts of money or sending the parts out for EDM or broaching?

[The Blight]

We actually do this at work with a large Index lathe, so it would seem possible to do the same thing on a mill.

[youngjim]

Drill a hole at each vertex to make the corner radius, drill & bore the biggest hole that will fit, mill the rest?

[RICHARD ZASTROW]

tkoden, Read the stuff at www.sommatool.com

They mention using on CNC machining centers and mills.

Dick Z

[PinnacleMachine]

Try these guys

http://www.slatertools.com/

JP

[peter@slater]

This rotary broaching video shows a 3/8" hex being cut on a lathe.
The tool holder will work on a CNC mill by turning the holder instead of the material.

Rotary Broaching

Rotary Broaching

[The Blight]

Thats the exact same tool we use on our index lathes! Easy to use, and fast. Might need a big and rigid machine, but should work.

[tkoden]

Originally Posted by peter@slater This rotary broaching video shows a 3/8" hex being cut on a lathe. The tool holder will work on a CNC mill by turning the holder instead of the material. Rotary Broaching

How rigid of a machine do you need to be able to do this? Is a VF1 going to be strong / stout enough to do this?

[peter@slater]

According to the Slater catalog, 1/2" hex broaching in 12L14 generates about 850 thrust lbs., I'm not sure if the VF1 can handle that. I read online it has up to 250 ft.lbs. of torque.
There is another important issue to consider: When rotary broaching, the spindle inside the tool holder spins freely. When contact is made with the part, no orientation is provided. If alignment of the flats of the hex to the part is required, you may have to fixture a broaching 'dog' to align them.

[peter@slater]

This video shows Rotary Broaching in a Mill. Stop Rods are shown mounted on the spindle side or work side. The orientation dog is used for alignment of the broach to the work piece.

YouTube - Slater Tools Orientation Dog Video

YouTube - Slater Tools Orientation Dog Video

[peter.blais]

FWIW, the spindle torque rating (250 ft-lb) has nothing to do with the required thrust force (850 lb)... One is a torque, the other a force...

I have no idea how much thrust the axis can generate but am pretty certain it is over 850 lb. It's all dependent on the axis servo torque and ball screw specs / size.

[yaddatrance]

We use a rotary broach in a smaller VMC... no problems... one trick we use to make it completely painless in harder materials is to drill then tap the holes first...