I use to be a machinist, technically, a tool and die maker. We made dies (which are molds essentially) for bolts out of carbide steel. Yes, they can be machined to very tight tolerances. The holes in our dies had a tolerance of +0.0002 - 0.0000 That’s plus two ten thousandths of of an inch minus nothing. For comparison a dollar bill is about 0.004" thick or 4 thousandths. Imagine slicing that dollar bill into 20 equally thick slices and that’s 0.0002 (or we would call it “two tenths”).
To get it to that point you are actually polishing it with finely ground diamond paste suspended in in a paste (we used cold cream).
The thing is, carbide is incredibly brittle. If you drop it the whole die can shatter or at least chip badly.
Interesting material but probably not a valid yoyo material.
Here’s an interesting aside. Carbide steel is so hard that it’s literally off the chart. That is, it’s too hard for the standard Rockwell scale of hardness to measure. So they beam x-rays through the material and measure how much comes out the other side. The stuff we used was either 25% or 16%. The 16% carbide means only 16% of the x-rays would pass through. Most of the dies were 25% and we had to custom make carbide reamers (drills) out of 16% to cut it. Then, we’d do all the final machining using diamonds as cutting tools. Somewhere I still have a little plastic case of diamonds that I used to cut carbide.