While boring, they are amazing. They just cut so well, much better than a steel bar.@WobblyHand I hear you on that! They do perform so beautifully though.
The front that mounts the insert usually are steel. So some sort of silver solder might be a good choice for the crack. You have nothing to lose at the moment. It's broken now. Worst that can happen is it stays broken. Maybe you can fix it. Silver braze is really strong. Find the thinnest wire you can buy, 1/16" is way too thick. The material is sold by weight (troy ounce!) due to the silver. If you can get 0.015" diameter or under it would be best. Safety-Silv by Harris is even food safety certified.@graham-xrf No the work was not. The force did skew the workpiece in the 4J pretty good and raised a giant burr in the back of the bore. Realigned the part and cleaned up the burr.
@Alcap IDK. I was wondering that. The front part that mounts the insert I think they're steel?? They must be silver soldered or brazed onto the carbide.