Broach Internal Square Drive? 4

[G2Jim]

Newbie here. Anyone have any experience broaching an internal square drive (1/2") in the end of a 17-4 PH stainless steel threaded shaft? The 2" shaft currently has a 1.5" hex drive on the end of it, but due to interference with another part needs to be cut off and an internal drive put in it. It's also hardened to Rc 38-45, so that may complicate matters. Any advice? Can it be done?
Jim

 

[MikeHalloran]

EDM.


Mike Halloran
Pembroke Pines, FL, USA

 

[unclesyd]

Another approach is to use a rotary broach.

http://www.slatertools.com/rotary_broaching.htm

 

[G2Jim]

Thank you both! The rotary broaching site is very informative. I don't have experience with EDM so this may sound ignorant, but can it be controlled closely enough to create an accurate internal square drive within the same tolerances as broaching?
Jim

 

[Kenneth]

Yes.

 

[EdStainless]

and another Yes for EDM.
Have you looked at an external 12 point configuration? That might be easier.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[G2Jim]

Thanks. For various reasons I am restricted to internal for this one application only. I'll do a little browsing on EDM, since I only know vaguely what it is.

 

[unclesyd]

You also give these people a try. They may recommend at shop.

http://www.wheelertool.com/

 

[tripleZ]

How many pieces are you talking about here? For production quantities I would look at broaching. For small batch quantities, EDM will be more cost-effective. As to EDM, you can hold 0.0001's (inches) depending on the time you're willing to put into the process and the surface finish you want.

Cost detractors to broaching: machine costs and specialty broaches. That hardness is going to be hell on the cutting edges long term (e.g. production quantities).

Cost detractors to EDM: machine costs and the cost of graphite for electrodes (if using a sinker). Wire costs aren't bad if you can cut straight thru (wire EDM). It all depends on what the part looks like.

You'll also want to look at how difficult the fixturing of the piece may be. Is the shaft long, part of a sub-assembly, etc.? That will affect your tank size, and thus potentially the shop that can burn the piece for you.

 

[G2Jim]

Thanks everyone, but it was only one part and has now been sent out to do. I took the easy route: identifying the desired dimensions/specs and letting the shop we sent it to determine how best to achieve it.

 

[Kenneth]

"Letting the shop decide how best to do it" may be completely fine in your application, but sometimes manufacturing methods (or their potential effects) must be fully understood and carefully weighted by the engineer designing a part (or a repair), and not left up to shop making it. Examples: thread330-96252 and thread2-104510

 

[NickE]

(Kenneth- Absolutely, ever seen what EDM does to fatigue life?)

 

[Kenneth]

Yup. My point exactly (and the subject covered in the thread links I provided).