popular science

36 POPULAR SCIENCE

London optician Edward Scarlett was among the irst to advertise “temple arms” for

spectacles around 1730. Later appendages featured a doorlike hinge that let users fold

their specs for travel. The irst models used metal posts to aix frames to arms. But, as

the reinement of industrial threading machines like lathes continued into the 20th

century, tiny stainless-steel screws took that job. Over time, the it has become stan-

dardised: Most frames now require fasteners with a shaft diameter of 1.4 mm, while

some thin wire frames use ones as small as 1.2 mm. The number of people globally

wearing some kind of corrective lenses is in the hundreds of millions. That’s a lot of

screws that can and do get loose.

ITEM:

Spectacle

screw

INVENTED:

20th century

USE:

Joining hinges

by Bryan Gardiner / photograph by The Voorhes FOR ANOTHER (ACTUAL-SIZE) SMALL WONDER, SEE PAGE 48