Group 9 was tasked to develop an adjustable width pulley that moved relative to a fixed center line for Micro Tool & Machine (MTM) as an industry-sponsored engineering design challenge for graduating mechanical engineering students. The adjustable pulley needs to have a range in width from 0 to 2.5 inches, maintain its centerline during adjustment, have positive lock for operation, and require no tools for adjustment nor locking. Group 9 found that this is a unique problem without an available solution. This report details the engineering design process to develop a functional concept to solve the problem. The first step to developing a solution was to define the problem, which includes defining the scope, needs, constraints, limitations, and expectations of the client. Once these were defined, Group 9 explored different methods for power, movement, and locking, which were then turned into initial concepts that were analyzed and presented to MTM. A single concept was then selected to develop into a functional model, which is outlined below. The model developed by Group 9 features a pulley body which freely rotates about a shaft with the use of roller bearings. The outer diameter of the pulley body has a left-hand thread on one end and a right-hand thread on the other, both threads have identical pitch and dimensions. A guide with corresponding threading on their inner diameter mate to each thread on the pulley body. After mating each guide to corresponding threads on the pulley body, their rotation is fixed to each other via dowels. Due to the reverse threading on one guide, when rotating in the same direction about the pulley body, both guides move towards the centerline or away from the centerline symmetrically. To lock the guides in place during operation, a lock washer was designed that features extrusions that index into voids on one of the guides. The lock washer has two flat spots on its inner diameter which match to flat spots machined onto the pulley body. The flat spots restrict the lock washer from rotating about the pulley. Once the extrusions of the lock washer are mated to the voids in the guide, the guide is restricted from rotating about the pulley. To prevent separation of the lock washer from the guide during operation, the lock washer is clamped to the guide via thumbscrews. Team 9 recommends implementing the design outlined in this report for a trial as it addresses all needs of MTM defined by the scope of the problem.