Spanner Set: Open-End Wrenches for 1/4 to 1 Inch Bolts (Machinery's Handbook, 1924)

A set of open-end spanners made to the standard dimensions in Machinery's Handbook. The jaw opening fits the nut of each bolt size, and head width, head thickness and length grow with it, so each spanner is strong enough for its own nut. Variable: the bolt size. The table gives each spanner's dimensions from 1/4 in up to 3 1/2 in bolts; this set covers 1/4 to 1 in. Source: Machinery's Handbook (1924), p. 848, Dimensions of Wrenches. Unknown: the steel and its hardening. Picture: the Handbook's page.