The diamond tip is ground with a taper then flattens for the cutter. Nothing holds the carbide in place except friction and it hasn't budged. A few folks expressed concern because it isn't form fit like Easy Wood Tools but that isn't necessary for holding it in place.
I've had less success with the radius cutter and will eventually replace it with a round carbide. Radius cutters don't do anything the other shapes don't do better. I suggest that you use square bar for square, radius, and diamond cutters otherwise the tool tends to spin when using the corners. This cutter has several chips where catches have flung it against the tool rest.
The tapped hole goes completely through.
The grinding doesn't have to be pretty to be functional. Leave steel under the cutter for support then grind a relief matching the angle on the carbide.
Soon I will be making a new one with a square bar. I purchase my carbides from AZ Carbide, excellent prices and customer service along with fast shipping. I have no financial interest in the company and receive no compensation for recommending them.