Tromblay Tool LLC – An Aviation-Focused Machine Shop In The New Golden Age of Small-Quantity Parts Production

by Ed Leineweber
Published in Midwest Flyer – December 2018/January 2019 issue

Over the last couple of years, I’ve been working on modifications to an existing kit aircraft design and prototyping the changes on a built aircraft. This activity has led me into the fascinating world of aviation-related design and manufacturing, focused on small production quantities made possible as never before by Computer-aided Design (CAD) and Computer Numerical Control (CNC) machining. Shops that employ these technologies, as well as tried-and-true old school machine shop tools, machines and techniques, can be found on airports, large and small, scattered around the country.

These shops have created what I think of as the New Golden Age of small quantity aircraft parts production and are having a big effect on vintage aircraft preservation, kit aircraft production and on-going efforts to keep legacy aircraft airworthy and in service. Tromblay Tool LLC, located on the East Troy, Wisconsin, municipal airport (57C), is one such shop, and the subject of this first of a series of articles I plan to write highlighting other such shops contributing to this New Golden Age.

Bill Tromblay started Tromblay Tool LLC in 2001 and was later joined by his brother Jim, and Jim’s son, Tony. Together, each morning they bring to the shop hangar a wealth of talent and experience where they create an engaging and productive blend of old school/new school metal-working activity. Decades-old lathes, mills and almost antique metal-shaping equipment stand alongside state-of-the-art CNC machines and CAD computers. A tour of their shop makes me wish I could stay on for an apprenticeship. (They even have an espresso machine!)

Bill is a journeyman machinist, certified welder, A&P/IA and pilot with 26 years’ experience. Jim is a journeyman machinist and certified welder with 30 years’ experience. Tony, a recent graduate of a local technical college, is an apprentice machinist with two years on the job.

These guys have drawn their aviation inspiration from Bill’s and Jim’s grandfather, Major Clement W. Tromblay, USAF, who flew B-24 bombers in China, Burma and India, and C-54 cargo planes in the 1948-49 Berlin Airlift. A tribute to Major Tromblay in the form of a memorial display featuring his photo, medals and other keepsakes hangs in the shop where the men can view it as they work.  The warmth and gentility of the Tromblays, their respect for their grandfather and his history, and their passion for their aeronautical and other work make this place something special.

Although Tromblay Tool also does work for the medical and food industries, their primary business is to custom design, machine and weld components for the aircraft industry. They manufacture parts with FAA Parts Manufacturing Approval (PMA), and Supplemental Type Certificates (STCs), as well as for Original Equipment Manufacturers (OEMs) and owner-produced parts under FAR §21.9. These parts are all either small production runs, prototypes or one-offs. If larger quantities are necessary, their work is sent on to a larger-scale fabricator.

As noted earlier, Tromblay Tool has a full line of CNC and manual equipment to handle any of their customers’ needs, including full aluminum forming and repair capability with the use of their English wheel, Pullmax machine and Planishing hammer. Bill, Jim and Tony make parts that are not supported by anyone else, and they take pride in their high-quality products.

In addition to parts production and smaller projects, Tromblay Tool is currently restoring a 1946 Aeronca Champ and a 1932 De Havilland Tiger Moth.

Tromblay Tool LLC is the perfect example of the New Golden Age of small-quantity, high-quality aircraft parts production making use of old school knowhow, combined with advances in high-tech parts production. May this down home, small-scale segment of the aircraft industry, continue to thrive in the coming years!

EDITOR’S NOTE: Ed Leineweber has been a pilot for nearly 40 years, an aircraft owner, Certified Flight Instructor, licensed aviation maintenance technician, FAA Safety Team member, and an attorney, licensed to practice law in Wisconsin. He is also a former fixed base operator and airport manager. Now, mostly retired from the legal profession, including 20 years as a circuit court judge, Ed focuses his limited practice in Aviation Law and Alternative Dispute Resolution, including Mediation. When not practicing law, he enjoys working in his shop at the airport on aircraft restorations and on his aircraft kit company, and spending time with family and friends. Readers are encouraged to suggest other candidates in the Midwest for future articles in this series. Please email Ed Leineweber at, or call (608) 604-6515.

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