USS flat washers have a large, wider body. SAE flat washers are machined to a tighter specification and have a smaller outside diameter. Flat Washer, Fits Bolt Size 3/4 in ,18-8 Stainless Steel 20 PK.
A machine screw, also called a stove bolt, is generally a smaller fastener threaded the entire length of its shank. Commonly used with flat or lockwashers.