Was this what you wanted?
I have attached my part.
What I did was to NOT use a 3D sketch to make the cut. I cut it using a 2D sketch and just blew the cut all the way through. I also didn't put in the fillets until AFTER I had the taper in.
Then I created a surface using a sketch that was offset from the curved top of the block 1/4" down and used that surface to create a "Split Line" around the inside of the hole cutout. This separated the two halves. Then I just applied a draft to the surfaces above the split line.
Then added the fillets.
I started the same way @Dan Pihlaja did, after the extrude cut I used a Asymmetric Chamfer instead of a cut.
Great approaches Dan and Andreas, thanks.
I didn't even think about using a chamfer. Unfortunately, it is the other side at needs the taper which is variable and not uniform.
Well, you still should be able to do it. I think that you can still do it the way that I have suggested, just swap the surface that is being drafted. And you can apply a draft to each face independently.
But if you need a specific shaped opening at the bottom, then you might want to try a lofted cut, with a sketch defining the beginning of the taper and another sketch at the bottom defining the shape of the opening.
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