[montie]

I have attached a print with some highlighting. How would you put the radiused groove in this part? Is the only way with some homemade shaping tool? We only have two parts so quantity is not a big thing. Thanks for your suggestions.

[Geof]

That is what I would do; a shopmade tool to broach it in the lathe. You would need to have spindle orientation and lock on the machine.

[kwhizz]

The lead-in and exit angle are the problem.........Form Tool (Spindle Off) programmed in a vertical mill ......Either fixture to rotate part or 4th axis

[fizzissist]

2 parts? 8 total grooves??

I'd probably broach it too, but on a mill with an indexer. If you can index the lathe accurately enough that's fine too...since the process is going to be the same as Geoff is suggesting.

One trick would be making a little pocket on the end of a bar for an insert with the radius you need, but mounted in such a way that you get the side clearance you need, and a nice positive rake....material suitability presumed.

Then, just broach away, taking suitably small cuts at a time.

Looks like you've got plenty of room inside the part for clearance, so making up the tool is going to be the most time consuming.

For a quicky high speed steel tool, use a ball mill giving the radius required into the side (along the length) of a bar of say, 3/4"dia, deep enough to give support to the broaching tool you'll insert into the groove and protruding enough to give the full depth of cut for the broaching plus some clearance.

Grind the end/face of a drill blank at a slight angle to give a sharp cutting edge, and braze it into the pocket you've milled in the bar. Grind relief as needed. A little flat at the cutting edge should even give a little burnishing. This should give ample rigidity, and allow you to use it in a mill or a lathe....even another radius tool on the other side of the shaft!

[Geof]

The lead-in and exit angle are the problem..........

I think you may be misinterpreting the drawing. The groove is straight and goes into the tapered transition on the bore; ta least that is my interpretation.