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CNC Gear Machining of a Steel Spur Cluster for the Defense Industry

At Reliance Gear Corporation, we have an expertise in machining gear parts that have been cultivated over four decades. Our high level of skill and experience was employed when a customer in the defense industry required the machining of a steel spur gear cluster. These spur clusters are used in transmission applications for tanks and armor personnel carriers. Using 9310 steel forgings, we engaged our advanced machining equipment to CNC turn and gear hob. Parameters are used to insure that post heat treat operations meet our customer's exact specifications as indicated per their supplied drawings. Post heat treat operations include additional CNC turning and precise "Crown" Spur tooth grinding which includes tip relieve and tip chamfering. We validate the quality levels analytically using our Hӧfler® ZP350 gear inspection machine. Upon completion of gear detail approvals, we perform non-destructive tests by nital etch and magnetic particle. We also post heat treat shape the external splines and verify criteria is being met by using a gaging system. This part also requires destructive testing to insure all aspects of the final part meet specific requirements. Shot peening concludes the manufacturing process.

These spur gear clusters are precision machined to diameters of 219.7 mm and lengths of 128 mm, with an external gear of 33 teeth and an external spline containing 34 teeth. To ensure the highest quality, many in-process tests and inspections are performed throughout the manufacturing process. These include dimensional and visual inspection, surface finish measurement, and others. We produce hundreds of these clusters a year for our defense industry client, meeting all MIL, ISO, and DIN standards.

To learn more about this project, please see the following information or feel free to contact us directly.

Steel Spur Cluster Project Highlights

Product Description
These parts are used in transmission applications for armor personal carriers and tanks
Capabilities Applied/Processes
CNC Turning
Gear Shaping
Gear Hobbing
Gear Grinding (Crown with Modified Profile)
I.D. Grinding
Shot Peening
Heat Treating
Part Marking
Overall Part Dimensions
Outside Diameter: 219.7 mm
Length: 128 mm
External Gear Data
  • Number of Teeth: 33
  • Normal Module: 6
  • P.A.: 20°
External Spline
  • Number of Teeth: 34
  • Normal Module: 5
  • P.A.: 30°
Tightest Tolerances
Operating Center Distance: ± 0.0009"
Quality ISO 7NP
Material Used
Steel Forging - 9310 Grade C
Material Finish
1.6 microns
In process testing/inspection performed
Dimensional Inspection, Visual Inspection, Gage Checks
Magnetic Particle Inspection, Gear Analytical Inspection, Surface Finish Measurement, Non Destructive Testing, Nital Etching, Destructive Testing
Industry for Use
Hundreds per Year
Standards Met
Customer Specifications
MIL Standards
DIN Standards
Product Name
Spur Cluster - Sun Gear