Let me start by saying that while you could print this model, it's not the intention (though I have). This is a model of the inner spiral staircase used in a dice tower I made. I thought it was a useful model so I wanted to share it in case anyone else wanted to use it to create their own dice tower with it.

The “staircase” is not smooth. In fact, it is about 360 steps, rotated 1 degree each. Every few steps, there are small bumps that keep dice from sliding down if they landed perfect enough to do so. It can be resized and modeled around as much as you would like. At it's current size, it's useable for D&D. It works best if your model creates a chute to the staircase.

I have included both STEP and STL files

The main image is a transparent render, as the photographs of the printed model weren't nearly as useful. However, MW requires this so I uploaded a shot looking down inside.