Below are how mine looked after the last operation. And, hey... It even looks good smoothed.
If this nut was supposed to be screwed around a bolt or if the inside was not supposed to be shown, we'd be finished by mirroring this model. We're going to mirror it, but we're also going to model the tracks on the inside...Displacement is for weaklings.
Mirror the geometry by duplicating it ( Check your settings, your last duplicate involved 5 duplicated. You might need to reset it ) scale it -1 in Z and combine the two meshes. Merge the vertices in the middle.
Now, since we're going to model the tracks I want you to split the inside 6 times. To get even results use "Split Edge Ring Tool" to split to the left and right side of the center edgeLoop and under INPUTS set the Weight to 0.5. Then you split between the new lines and the center to split this row of faces in half too. Continue this till you hva 7 edgeLoops on the inside of the nut. When you have done that your mesh should look a lot like this and you have eight rows of faces to work on.
The tracks isn't straight so we have to cut it to get them diagonal. I'm going to cut three faces per edgeRing. Let me use a cube to illustrate how I'll proceed with the cutting. Use your favourite splitting method. I used Split Polygons and under INPUTS I set the weight to 0.66 and 0.33. Note that when you split the upper half you get 1.00, 0.66, 0.33 and 0.00, but when you cut the lower half this tends to flip so it reverses the order to 0.00, 0.33, 0.66, 1.00. So when you cut, try and cut somewhere near where the cut is supposed to be so you're not stuck with 0.55778 everywhere. It'll get bitchy when you're going to tweek the inputs
And this is how the first split will look when splitting the nut: ( Selected edges are the ones I want to delete ) It's easier to do this operation if you rotate the nut 90 degrees in the x-axis because orientation is a bit tricky when the nut is standing like it does now
And here is a sideview wire. You can clearly see that this is the track we want.
Now all you have to do is split up the whole thing. When you delete the edges crossing the newly created spiral, you'll be able to see where the next split should go. When you have split one spiral go back up to where it started, cut a new spiral on the edge right below and do a second split. When you reach the bottom go back up to where you started the second split and cut one step backwards. ( Notice that I do not cut the top- and bottom edge-ring
