You all will realise in the anime when time can be displayed correctly.
Does kakashi know where or when obito will appear... no. So obito's body suddenly appears in the other dimension, kakashi doesn't have time to do hand signs so he takes a whack at it.
Obito bends down and coughs out blood and kakashi takes more whacks at him and obito quickly runs out of naruto's punch so he can exit the dimension and kakashi returns, before obito can teleport back into that dimension and **** him up.
Also the amount of chakra kakashi has as well, he needs to be able to get out before it's to late.
People need to think clearly.