Ajax TOCCO Magnethermic and Ohio Crankshaft are wholly owned subsiaries of Park Ohio Holdings. Park Ohio is a diversified international company providing world-class customers with a supply-chain management outsourcing service, capital equipment used on their production lines and manufactured components used to assemble their products. Headquartered in Cleveland, Ohio, Park Ohio operates more than 125 manufacturing sites and supply-chain logistics facilities worldwide.

Why is this spring so important? Both TOCCO and Park Ohio owe their beginnings to two young engineers, William C. Dunn and Francis S. Denneen, who started the Ohio Crankshaft company in May 1920 in a small garage in Cleveland, Ohio. These companies are celebrating 100 years of manufacturing excellence this month, which is no small accomplishment. 

Park Ohio was created in 1967 by the merger of Park Drop Forge, which was founded in 1907 and manufactured closed-die crankshaft locomotive forgings and landing-gear forgings, and Ohio Crankshaft. A key part of the story was the development of a revolutionary process and product that would withstand the test of time and showcase the ingenuity of Ohio Crankshaft’s two founders, who had an incredible futuristic manufacturing vision.


The TOCCO Process

The process of induction heating (originally discovered in 1831 by Michael Faraday) was perfected by Ohio Crankshaft’s Dunn and Denneen in 1934 to improve the wear life of crankshafts and camshafts. They named it the TOCCO process (an acronym for The Ohio Crankshaft Company). 



The product(s) were vastly superior camshafts and crankshafts that would provide efficient and long-lasting reliable power for the automotive, trucking, bus, locomotive and marine industries. It was not uncommon for crankshafts to show wear in engines with only 30,000-50,000 miles during this era. 



The TOCCO process allowed for localized hardening of parts with a consistent depth, excellent metallurgical properties and a surface-hardened zone that blends in without a demarcation zone, meaning no flaking or spalling of metal and with very little part distortion. The result is a hardening process that would take mere seconds versus other processes of the era – such as nitriding, chromium plating and cyaniding – that could take 24 hours (or longer). The TOCCO process produced crankshafts that increased over-the-road truck lifetimes to more than 500,000 miles.

Not only was the TOCCO process used to induction harden Ohio’s crankshafts, the two founders designed and built TOCCO machinery systems to induction harden parts, both large and small and both simple and intricate in design, for all industries imaginable. 

Although the induction industry has become global, with mergers, start-ups and many once-familiar names now changed or merged, the basic principles, theories and physics of induction haven’t changed much. However, the electronics most certainly have. Motor generators and radio-tube-type oscillators have become pretty much a thing of the past. They have been replaced by digital electronics, wireless communications to solid-state power supplies, and controls and systems that are much more powerful, repeatable and accurate. 

Ajax TOCCO currently has a 200-kW, 20-KHZ induction hardening system that is built and ready to ship awaiting the customer’s final approval of metallurgical-specimens’ test and setup pieces. This system has all the bells and whistles that are now considered commonplace: wireless interface from the power supply (Windows-driven) to the machine controls/computer. 

The system is equipped with a barcode reader that allows all processing information to induction harden the part. Quenchant flow, pressure, temperature, heating times, kW and seconds are all logged on a part-to-part basis, recording and trending the history of each part run. Automatic system shutoff if any operating parameters are not met, quench concentration, temperature, part alignment, etc. take most of the “oops” out of the process. There are no more lost operating manuals or machine drawings because they are stored within the controls for easy retrieval and reference. 



The future of induction will acclimate itself to products and exotic materials that haven’t even yet been discovered or imagined. Induction technology and processes will continue to evolve and improve to meet the ever-changing demands of the automotive, aeronautical and medical industries. The automotive industry, even though it will become more electric-driven, will still require the durability of the necessary transmission, suspension and other hardware components that induction hardening can deliver.

So much is owed to two young enterprising engineers who had a vision and a dream 100 years ago that has stood the test of time and the huge role they had in the metalworking industry. And it all began in a small garage in the shadows of Cleveland’s once-booming steel industry.