Last time, we talked about coarse splined knobs and fine splined knobs. Some might be curious about whether you can fit one to the other. As with everything DIY, there is always a way to get something into the wrong-sized space. Yes, you could force either a coarse or fine splined knob onto the wrong control shaft and if you apply enough pressure it will go on. But it will never be a perfect fit and be completely true. Therefore any super fine volume or tone adjustments will be a little harder. It will also be a lot harder to remove in future.
However, if you have a set-screw knob, you can install it onto a coarse or fine split-shaft potentiometer (you might need a very thin sleeve to place around the control shaft). The side-screw design should secure the knob in place, but make sure that you screw into the side of one of the two shafts, not where they meet.
If you have bought the wrong-sized knobs and they don’t easily fit on your guitar, then the best advice is to put it down to experience and buy some that do. They can then be quickly and easily fitted to your guitar perfectly, allowing you precise control over your volume and tone knobs to get you the sounds you want.