The precision you demand, geared to your specifications.
For more than 135 years, Overton Chicago Gear has delivered custom open gearing and complete gear drives to the industries that keep the world moving — engineered, cut, and inspected under one roof.
- 1888
- Manufacturing since
- 160"
- Gears up to
- AGMA
- Founding member
Every process under one roof
From the first drawing to final inspection, we control the entire gear-making process in Addison — so your parts stay on schedule and on spec.
Engineering & design
In-house gear engineering, reverse engineering, and full 3D modeling from print, sample, or concept.
Gear cutting & milling
More 5-axis milling capacity than any gear maker in North America — cut to AGMA 11 without grinding.
Heat treatment
In-house carburizing and one of the largest press-quench operations in North America.
Gear metrology
A modern inspection lab with CMM systems verifying every tooth to AGMA, ISO, and DIN tolerances.
Assembly & repair
Complete gearbox assembly, emergency gear repair, and rebuilds that get your equipment running.
Quality assurance
ISO 9001 registered systems with full documentation traceable through every stage of production.
Precision gears, built to spec
Spur, helical, bevel, and worm gearing in diameters up to 160 inches — cut, hardened, and inspected for the most demanding drivetrains on earth.
Spur Gears
Precision straight-tooth spur gears cut to AGMA 11 in diameters up to 160 inches — the workhorse of heavy power transmission.
Helical & Double Helical
Single, double helical, and herringbone gears for smooth, quiet, high-load meshing in demanding drivetrains.
Bevel Gears
Spiral, straight, and skew bevel gears for reliable right-angle and intersecting-shaft power transmission.
Worm Gears
Worm and worm-wheel sets for high reduction ratios, compact drives, and self-locking motion control.
Custom Gearboxes
Complete custom gear drives — designed, built to print, and assembled with our own precision gearing.
Repair & Reverse Engineering
Emergency gear repair, rebuilds, and reverse engineering — get critical equipment back in service fast.
Capabilities most gear shops can't match
Vertical integration is our advantage. Because engineering, cutting, heat treatment, and inspection all happen in Addison, we hold tighter tolerances and shorter lead times than shops that outsource.
- AGMA 11 accuracy cut without grinding on our large-capacity 5-axis mills
- One of the largest press-quench operations in North America for controlled distortion
- Complete gear metrology lab verifying every tooth to AGMA, ISO, and DIN
- Reverse engineering from a worn sample when no print or drawing exists
Made in Addison, Illinois since 1888
Overton Chicago Gear unites the heritage of Overton Gear, Chicago Gear, D.O. James, and Illinois Gear under one ISO 9001-registered roof — with every step of the process handled in house.
- 5-axis gear milling
- Cut to AGMA 11 accuracy
- Internal & external gears
- Diameters up to 160 inches
- Carburizing & press quenching
- Surface temper etch to 60"
- CMM & gear metrology lab
- Reverse engineering
The industries we help power
When failure isn't an option, the heaviest industries in the world turn to Overton Chicago Gear for gearing that keeps critical equipment running.
Oil & Gas
Pump, compressor, and mud-pump gearing engineered for continuous upstream and downstream service.
Fracturing
High-strength gearing for frac pumps and pressure-pumping fleets that endure extreme, repeated shock loads.
Mining
Bevel, spur, and girth gearing for cone crushers, mills, shovels, and earth-moving equipment.
Marine
Propulsion, winch, and deck-machinery gearing built to marine standards for reliability far from shore.
Wind Energy
Precision gearing and gearbox components for wind turbine drivetrains and yaw-and-pitch systems.
Cement Processing
Girth gears, pinions, and kiln drives for cement plants that run around the clock in abrasive conditions.
Locomotion
Traction and drive gearing for locomotives and rail equipment built for high-mileage reliability.
Metal Processing
Pinion stands, drive gears, and gearboxes for rolling mills and metal-processing lines under constant heat and tonnage.
Let's get your gears turning
Send us a print, a sample, or a set of requirements. Our engineers will help you spec the right gearing and get precision parts back to you — fast.