The first part has a weld to something else while the second is being welded to the first. The first part is already being cf:inverse and the second part is being cf:inverse. The first cf:inverse is good but the second parts cf:inverse makes either the first one go somewhere else or the second one go else where.
I think I see what you mean. I’ll try my best to explain and help out.
If you are hoping for a tool with multiple parts to it, like so:
Weld constraints will be the best option. To do this, simply create one inside the tool, make Part0 the tool you want to attach, and Part1 the handle. This should work perfectly, leaving you with this as the end result.
Maybe you could try using a WeldConstraint instead of a weld? I don’t think WeldConstraints use C0/C1. Or if you mean you want it to be able to rotate freely without affecting the first part, maybe you’re looking for a HingeConstraint?