Engine Systems

Business Situation:

The proven advanced technology in locomotive engine design and the strict requirements in meeting the U.S. EPA’s Tier 2 & Tier 3 emissions for engines have made this OEM engine one of the “10 Locomotives that Changed Railroad.”

As a result of this and the increasing popular demand for this OEM engine, Connecting Rod capacity was required to keep up with our OEM’s customer demand. The decision was made by the OEM not to increase In-House machining capacity but to look for an outside machining partner that could supplement the volumes as the market increased.

Technical Situation: Connecting Rod

The current OEM state was manufacturing the connecting rod utilizing technology that required 8+ staging operations using 8+ machines. These stages and machines required extensive capital and a large manufacturing space to accommodate the required operations. These are as follows:

  • CNC machine for initial qualification / roughing operation of Con Rod
  • CNC machine to finish roughing operations
  • Saw machine to separate cap from rod
  • Special Gun Drilling machine to drill from Wrist Pin Bore to Crank Bore requiring connection hole plug hardware
  • CNC machine to prep split line for creep feed grind and assembly
  • Dedicated Creep Feed Grinder for Split Line Serrations
  • Assembly of cap to rod
  • CNC machines to rough critical Bores
  • CNC machine to finish critical bores

The OEM discovered that additional capital, labor, and manufacturing space required were not available. An alternative solution was needed and the challenges were finding a suitable outside machining supplier that had the expertise in engine machining, available capital and space to manufacture the connecting rod.

Additionally- The OEM was looking to have the cost meet an internal target that would keep them competitive and successful in the marketplace.


HN Precision specializes in machining using state of the art CNC machining centers while mastering the concept of design for manufacture. Our goal was to consolidate as many staging requirements as possible while reducing the number of machines required to finish a connecting rod. HN Precision’s goal was to include all initial roughing operations, gun drilling operation, grinding of serrations, and finishing operations in a single CNC cell.

The industry standard was utilizing a separate gun drilling machine and separate Creep Feed Grinder for those operations.

The end result was an industry first utilizing a CNC cell consisting of 3 machines while reducing the amount of staging to 5. This CNC cell included the following operations:

  • All initial roughing operations
  • Saw operation
  • Gun Drilling and Grinding of Serrations
  • Assembly of cap to rod
  • All Final roughing and finishing operations

Gun Drilling:
The current OEM method was utilizing a special dedicated gun drill machine to drill from the wrist pin bore through to the crank. This also required connection hole plug hardware that sometimes dislodged in the engine during use. A service call and tear-down was the only option to fix this event.

HN Precision’s method was to utilize the CNC machine to drill from the Crank Bore to the Wrist Pin Bore. This method allowed for the elimination of the hole plug hardware while increasing reliability of the engine. This method also eliminated the need for a dedicated drilling machine.

Grinding of Serrations:
The current OEM method was utilizing a dedicated Creep Feed Grinder to grind the serrations of the bore. This caused extra staging and a dedicated machine to complete.

HN Precision’s method was an industry first to grind the serrations in a CNC machine which eliminating the need for extra staging and extra dedicated machine.


HN Precision partnered with our OEM to meet the challenges and demand of the marketplace. Through concurrent engineering with the customer, HN Precision has been able to improve the quality of the engine, increase Con Rod demand, achieve costs targets, and develop new processes that will assist our OEM in becoming the world leader in locomotive engines.

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Engine Systems
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