How keys are made

Linus Yale Sr. invented the modern pin tumbler lock in 1848, and a key is just its cheap, shaped partner.

stations: 6
things upstream: 27
raw sources: 13
steps from the ground: 5

The short version

A house key usually starts as a blank punched from flat sheet brass or nickel silver in a heavy press. Long grooves milled down the blade fit it to one style of keyway, and it can then be plated. Blanks ship uncut. A key machine traces an original with a guide while a spinning wheel copies its notches into the blank.

Punch the blank

A heavy press punches key shapes from flat sheet metal, usually brass or nickel silver because they are soft enough to work and to cut later. Some factories die-cast a rough shape instead.

Goes in
Brass
Size the blade

Edges are sheared clean, and each blank is milled to the correct thickness and trimmed to length.
Mill the grooves

Cutters or a stamping die run lengthwise down the blade, forming the slots that match the shape of the keyhole. The cross-section is what ties a blank to a particular brand or style of lock.
Plate it

A 1942 patent sends its stamped blank straight to plating once the slots are in. Finished keys commonly come as plated brass or nickel silver, and the blanks then ship uncut to locksmiths and hardware stores.

Goes in
Nickel
Clamp beside the original

A duplicating machine holds the original and a matching blank side by side in separate clamps. Both are lined up by the same reference edge.
Trace the notches

A tracer rides along the peaks and valleys of the original while a linked cutter wheel carves the same pattern into the blank. Each notch has to match the lock it was made for.

End of the lineKey

Worth repeating

Archaeologists found the oldest known lock at Nineveh in ancient Assyria, and people have used locks for more than 6000 years.
Robert Barron invented the lever tumbler lock in 1778.
American Linus Yale Sr. invented the modern pin tumbler lock in 1848.