Outside Double-D Washers - Specialty Anti-Rotation Washers

Outside Double-D Washer Frequently Asked Questions

Below are answers to some of the most common questions about outside double-D washers.

What are outside double-D washers?
Outside double-D washers feature two parallel flat edges on the outer diameter, creating a double-D outer profile with a round inner bore. The two opposing flats allow the washer to seat securely in a rectangular or square slot and prevent rotation in demanding mechanical applications. Superior Washer stocks 5 outside double-D configurations with IDs from 0.191" to 0.485" and ODs from 0.745" to 1.5".

What is the difference between outside D-shaped and outside double-D washers?
An outside D-shaped washer has one flat on the OD for seating against a single edge. An outside double-D washer has two opposing flats on the OD, which engage both walls of a rectangular or square slot to provide positive retention and anti-rotation from two directions. Double-D is used when a single flat is not sufficient to prevent movement in the housing or slot.

What applications use outside double-D washers?
Outside double-D washers are used in rectangular slots, square housings, and keyed recesses where the washer must be retained positively against rotation and lateral movement. Common applications include gearbox housings, actuator assemblies, precision instruments, and custom mechanical devices where the mounting geometry dictates a non-round outer profile.

What materials are outside double-D washers available in?
Outside double-D washers are produced in steel, stainless steel, brass, and aluminum. Contact us to specify the material needed for your application.

Can you produce custom outside double-D washers?
Yes. We manufacture custom outside double-D washers to your OD, ID, thickness, and flat-to-flat specifications. Contact us via the Quick Quote form or call NY (631) 273-8282 or SC (803) 366-3250.

Are your outside double-D washers made in the USA?
Yes. All outside double-D washers are manufactured in the United States under our ISO 9001:2015 certified Quality Management System at our Hauppauge, NY and Rock Hill, SC facilities.

Need a single-flat OD or a different shape entirely? Browse the full flat washers catalog to see all shapes and materials available.