I don't believe either that this tool is for a cannon.
It would be very impractical to use a tool that has to be screwed on and of and changed several times for every shot.
A cannon is a long distance weapon, which was shot more often than a normal musket during battle (it is ussually easier to load a weapon when you are not fired at !!) Cannons beeing out of range for most of the battle, they where relatively save i assume.. eventhough they would be targeted as well when possible.
Coming back to my first point, the cannon would be shot using a ramrod (1), cleaned (2) and in the case of a falconet or small caliber cannon, you might also get the ball out again (3)
So if such a rod would exist of 2 parts, you would constanly be changing.. which makes no sence when all you want to do is pound the guts out of some people a few hundred yards away.
Attached is an artillery cleaning rod, most likely american revolution (about 8feet long, roughly 180cm).
