Cutting Custom Threads/Undercuts

[campbellqn]

Does anyone have any good ideas on how to cut the threads in the images below? They aren't a standard size thread, and there are 4 of them. I've tried trace, thread, 3d contour using thread mills and dovetails but I can't seem to get it quite right.

Any help would be appericated

[Steinwerks]

Using the Thread 2D toolpath you can specify the pitch, so I would change the model to a cosmetic thread instead of modeled.

Personally I like to model threadmilled holes at nominal OD diameter and use Wear Offset to dial in the thread at the machine. Otherwise you can use the minor diameter and specify the Pitch Diameter Offset.

[campbellqn]

and how would you go about leaving the other bits intact? 

[Steinwerks]

I'm not sure what you mean by other bits in this scenario.

Can you export your file as a .F3D and share it here?

[campbellqn]

Sorry "other bits" wasn't all that informative. 

I've attached the file. What I meant by other bits is the area that lacks threads as it can't be threads all the way down, its acting as more of a twist lock.

[Steinwerks]

Ah you are cutting the nodules not the thread in the center of the part.

This thing is definitely a challenge. It might almost be simpler to machine the bottom of the geometry through the clearance pockets. I will see if I can spend some time on it tomorrow. What tooling do you have to work with, and what machinery is available? I think turning the part blank is going to give you the simplest solution, but it's still not going to be simple.

[campbellqn]

I have a tormach 1100, with a pretty standard set of end Mills. I was thinking of trying to use either a dovetail cutter or thread mill in conjunction with a slotting mill or reduced shank endmill. But I can purchase what ever is needed.

The slots in the bottom were added only to get to those threads from the other side if necessary, but if I can reach them from the top then I don't have to worry about those.

Thank you for the help!