Padlock Manufacturing: From Roman Locks to ABB Robots

Padlock manufacturing looks simple from the outside. A padlock is a steel shackle, a body and a small cylinder of pins and springs. Making millions of them, each opening only for its own key and each resisting a bolt cutter, takes more care than that suggests. This post follows the padlock from Roman iron to Harry Soref's laminated Master Lock of 1921, then to the plants of today, where ASSA ABLOY's purchase of the US maker PACLOCK in September 2026 put American padlock making back in the news. It also asks where ABB robots such as YuMi and the IRB 1200 could fit.

A Master padlock with a round steel body hangs open from a wooden fence. Photo: Tony Alter / Wikimedia Commons (CC BY 2.0)

How padlocks went from forged iron to stacked steel

Padlocks are far older than the modern lock trade. Wikipedia dates them to somewhere between 500 BC and 300 AD in the Roman world, and the photo here shows a Roman padlock from Pompeii that is now in the museum in Naples. In China padlocks appear from the late Eastern Han dynasty, between 25 and 220 AD. A spring tine padlock found at the Jorvik Viking settlement in York is dated to 850 AD. A smith forged and filed each of these by hand, one at a time.

A Roman padlock from Pompeii, now in the National Archaeological Museum in Naples. Photo: Avandalen / Wikimedia Commons (CC0)

Machines took over in stages. Yale & Towne received an 1877 patent for a padlock with a lever cartridge and a shackle that swung away. Padlock bodies machined from a solid block became economical in the early 20th century as electricity spread, and Corbin and Eagle are credited with early machined block designs. In 1908 Adams & Westlake patented a stamped, riveted switch lock. The French advertisement shown here, from 1923, sold Yale padlocks as built to resist anywhere and everywhere.

A 1923 advertisement for Yale padlocks in the French magazine L'Illustration. Photo: L'Illustration via Wikimedia Commons (public domain)

The cheapest strong body came from Milwaukee. Harry Soref designed a padlock body from laminated steel layers in 1919, and in 1921 he, P. E. Yolles and Sam Stahl founded Master Lock there with about five employees. The company received the first patent for a laminated lock design in 1924. Punched sheet metal plates, each with holes for the locking parts, were stacked and riveted into a body. Plates like these can be stamped in a press, which suits a production line. A Super Bowl advertisement in 1974, "Tough Under Fire", made the brand famous.

A Master Lock commercial padlock on a cable at Lewis and Clark State Park, Iowa, 2018. Photo: Tony Webster / Wikimedia Commons (CC BY 2.0)

Padlock manufacturing today and where ABB robots fit

On September 16, 2026, ASSA ABLOY announced that it had bought the Pacific Lock Company, known as PACLOCK, a US padlock and security hardware maker. PACLOCK was founded in 1998, has about 40 employees and makes its products in Valencia, California. Its 2025 sales were about 17 million US dollars. It will sit in ASSA ABLOY's Residential Business Segment in the Americas Division. Master Lock went the other way: it began moving much of its manufacturing to China in 1993 and closed its Milwaukee plant in March 2024, a story covered in our post on door and window hardware.

A brass padlock with its key in the cylinder. Photo: MichaelFrey / Wikimedia Commons (CC BY-SA 3.0)

The steps in a padlock plant have changed less than the machines. Laminated bodies are still stamped, stacked and riveted. Solid bodies are machined from a block. Shackles are cut from rod, bent in a press and tempered, and cylinders get their pins and springs before the plug goes into the shell. Wikipedia notes that even after Master Lock moved most production abroad, its Milwaukee plant kept some output through heavily automated processes. Every step still ends with a part that someone, or something, has to load, unload and pass to the next machine, which is the work robots take on first.

ABB robots moving panels between presses on a stamping line. Photo: ABB

ABB has no documented padlock customer in the sources used here, so what follows is a possibility. The dual arm YuMi IRB 14000 is built for small parts assembly beside people, and a pin and spring insertion bench is the kind of job it could take. The new generation IRB 1200, launched in 2025, is a compact arm for machine tending and small parts, which suits loading a plate press or a drilling station. Larger ABB robots already tend stamping lines, so the same approach could move steel plates between presses. More examples are on the ABB robot use cases page.

ABB YuMi assembling small parts beside a lab worker. Photo: ABB

What comes next for padlock making

Variety is the main difficulty. One padlock family comes in several body sizes, finishes and keying options, and ASSA ABLOY's Lucas Boselli, head of its Americas Division, said PACLOCK's customized security solutions make it a trusted partner for customers whose needs go beyond standard offerings. Short runs are hard on robots, because each new part can need new grippers and a new program. Engineers can build and test a loading sequence in RobotStudio before the cell stops for a changeover, which keeps that cost lower.

The new generation ABB IRB 1200, a compact six axis arm for fast small part work. Photo: ABB

Programming is the second obstacle. A small lock maker may have no robot programmer, and Wizard easy programming on ABB's cobots lets shop staff build simple tasks from graphical blocks. Safety matters on a shared bench as well, and SafeMove can monitor the speed and working zones of an arm when a person steps close. The graphical programming page of the RobotStudio course shows what block based programming looks like. Skilled setters will still decide how a cell is tuned.

Wizard Easy Programming blocks on an ABB FlexPendant. Photo: ABB

The larger open question is where padlocks get made. Master Lock moved much of its production abroad from 1993 and PACLOCK builds in California, so location has been a live choice. Automation is one lever for keeping production near buyers, though a cell still has to pay for itself on the volume of a single plant. Key codes and pin heights are sensitive data, so a lock maker also has to control who can read and change the programs. Cost, variants and security will decide how far robots go.

A sheet metal padlock marked ABUS, from around 1950. Photo: R. Henrik Nilsson / Wikimedia Commons (CC BY 4.0)

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