The ornamental design for a knife for replaceable blades, as shown and described.
FIG. 1 is a right-side elevational view of a knife for replaceable blades showing the new design, the left-side elevational view being mirror symmetrical thereto, the dot-dash showing of the blade representing the outline of one of a set of blades which are interchangeable with one another and can be engaged in the handle shown;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a right side elevational view similar to FIG. 1 but showing the blade separated from the handle and the blade-locking lever in its outer position; and,
FIG. 4 is a rear view of the handle and blade of FIG. 3.
The broken line portions of the disclosure are for illustrative purposes only and form no part of the claimed design.