I think you will stuggke trying to index that type of part. You can think of cutting towards the center to the depth of half of the helix diameter. After that it is undercut city. You can look for a cam program that can 5 axis or “lollypop” but very advanced and will be very hard.

Protocam is 3d printing services. You could model that in MoI in a few minutes and email and have that printed easy.

Using a lathe you could cut the interior, minus the helix, easy. Then attach the helix parts after.