A portable adjustable washer cutter (12) and improved sealing washer blank (14) useful in telecommunications applications. The cutter (12) comprises an essentially flat frame (38) carrying a rotatable shaft (44) and a platform (58) placed opposite thereto for mounting a sealing washer blank (14) in which a desired central opening is to be cut. An improved sealing washer blank (14) having a small central opening (16) and a small opening (18) along its periphery can be easily mounted on the cutter by insertion of protruding members (60, 70) on the cutter through these openings. The sealing washer blank (14) is cut by means of a blade (54) mounted on a member (52) attached to the bottom of the shaft (44). In a preferred embodiment, the sealing washer blank (14) is provided with concentric annular ribs (24), the sealing washer blank being cut at a position between ribs.