Place bread in a large mixing bowl with water to cover; let stand 5 minutes. Drain, squeezing excess water from bread; return to mixing bowl. Add eggs, mayonnaise, Worcestershire sauce, salt, mustard, and pepper; mix well. Fold in crabmeat.
Shape mixture into 12 patties; roll each in breadcrumbs. Fry in deep hot oil (350°) until golden brown, turning once. Drain on paper towels.
Place 1 crab cake in each bun. Serve warm with tartar sauce.