I've been looking into this, too. As posted a 4th axis on a vertical mill will work. Those rotary broaches are awesome. They are also mondo $.
Do you plan on doing a hundred of the same splines or just one here and there, whatever it is? I think you'd be better off with a mill in any case. It's all in the tooling. I am still building up my machine shop at home and the machines are only 50% of the cost so far!
I think a Dremel tool with a thin cut off is the way to go.
As was mentioned before you need a lathe - and I'd suggest a very substantial lathe becuase you will be hard turning the shaft and the cutting pressures are very high. Here's my lathe:
For scale, that's a 12" 4 jaw and a CA sized quick change tool post. The lathe doesn't need to turn fast, but it does need to be really rigid. I use a live center and I also use the steady rest to help fight chatter and limit deflection of the axle shaft when I am cutting.
You also need a mill, a spline cutter and an indexer.
I've upgraded since I made that post (it's been almost 4 years). The first upgrade was to sell my Bridgeport and get a Gorton vertical mill and put a DRO on it and use that for cutting splines - WAY better than the horizontal for ease of use and productivity. The second upgrade was to cut splines on my vertical CNC. I'm still indexing by hand, so I basically run the program to cut one spline, index and then run the same program again until I'm done. It's a PITA though and between blanking the shaft and the actual spline cutting it takes over an hour. I generally won't do that job for other people, unless I owe them a favor or they have some good Jeep parts to trade
A forum community dedicated to custom off-road vehicle owners and enthusiasts. Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more!