You need more tension on most lever locks than pin tumbler locks,
If you can not tension the bolt enough to bind the levers without the tool breaking its likely not up to it however a common problem for people new to 2 in 1's is for them to leave/make the tensioning tang too long,
If the bolt throwing tang is too long is can catch or even jam on the 'V' of the bolt, if this happens you think you are putting tension on but in fact your not and simply turning against a jam up,
To check for this you simply look to see if the bolt moves in and out slightly when you put tension on or take it off, in and out is differant to a wiggle up and down by the way

anything in contact with any part of the bolt will give the wiggle now and again so make sure it is moving in and out,
If you want further info including pics on this check my guide out on 2 in 1's,
Another possable reason is the two tangs may not always be the same size, some padlocks use a shrter bolt thrower than the part that lifts the levers,