Sunnen Honing Equipment

About Sunnen Products Company

Few names in precision machining carry the weight of Sunnen Products Company. Sunnen was founded in 1924 by Joseph Sunnen, a young inventor who patented his first valve lifter tool while working in his brother's auto garage in St. Louis, Missouri. Lacking funds for a storefront, Joe loaded his tools into a converted 1916 Hupmobile and drove from garage to garage, selling his innovations directly to the mechanics who needed them most. That entrepreneurial spirit paid off quickly — by 1928, Sunnen had designed the first manual cylinder hone for auto garages, planting the company's roots firmly in precision bore solutions.

A century later, Sunnen has grown into what is widely recognized as the world's largest vertically integrated manufacturer of precision honing systems, with sales, service, and manufacturing facilities spanning multiple countries. The company controls all aspects of its product development — from research and design through manufacturing and customer support — ensuring that every tool, abrasive, and machine meets exacting standards. That vertical integration extends to Sunnen's specialized abrasives and tooling, giving engine builders and machine shops a single, trusted source for everything they need to achieve perfect bore geometry.

A Century of Honing Innovation

Sunnen's legacy is built on a deceptively simple principle: that precise bore geometry is fundamental to how engines perform, seal, and last. Sunnen engine cylinder hones have been the benchmark for cylinder finishing since the company introduced the very first portable manual hone in 1928. Today's Sunnen honing systems are capable of controlling bore size to within ten millionths of an inch, correcting geometric errors and producing specific surface finishes engineered to optimize lubrication and ring seal. That level of precision is why Sunnen is the official honing equipment partner of Hendrick Motorsports — where winning margins are measured in fractions of a second, not fractions of an inch.

At the core of the honing process are the abrasive tools themselves. Sunnen honing stones are engineered to work in concert with Sunnen mandrels and honing machines. Available in a wide range of grits and bore-size ranges — from fine finishing stones to aggressive stock-removal abrasives — Sunnen stones are formulated for specific materials and applications, whether you're honing cast iron cylinder walls, Nikasil-coated bores, or precision valve guides and lifter bores. Using purpose-built abrasives matched to the honing tool is what separates a professional bore job from a rough approximation.

Proper lubrication is equally critical during honing, which is why Sunnen developed its own dedicated honing oil. Honing oil serves multiple functions simultaneously: it cools the abrasive stones and workpiece, flushes away swarf and debris, and helps control the cutting action of the stones to produce a consistent, repeatable surface finish. Using the right honing fluid is not an afterthought — it directly affects stone life, bore finish quality, and the accuracy of the final result.

Trusted by Engine Builders Worldwide

From independent machine shops to NASCAR race teams, Sunnen has earned its reputation by delivering tools that perform when precision matters most. Whether you're rebuilding a street engine, refreshing a performance powerplant, or preparing a racing engine to compete at the highest levels, Sunnen's honing stones, cylinder hones, and honing oil represent a complete, professionally integrated system — one that has been refined over a hundred years of real-world engine building.