ECG Slot Grinding of Castle Nuts Eliminates Need for Secondary Operations

March 24, 2021
Using electrochemical grinding (ECG) to form the slots on castellated nuts can generate as much as 70% savings in productivity by eliminating the need for secondary operations.

Castle nuts, also referred to as castellated nuts, are used for applications in aerospace and automotive markets where the nut cannot loosen. A cotter pin or safety wire is inserted through a cross-drilled bolt extending through the opposing slots to mechanically prevent the nut from loosening. Without the Castle Nut, the nut would separate from its shaft potentially leading to catastrophic results.

The slotting operation requires three cuts per part, cutting two slots per pass. Slitting saws, abrasive grinders, wire EDM, and sinker EDM are popular mechanical and abrasive processes used for slotting castle nuts. These processes require frequent wheel dressing or saw changing, dramatically reducing productivity and throughput. Current manufacturing processes can distort the slot, damage the slot or deform the thread. Secondary deburring or re-tapping is often required after slotting. This results in increased scrap rates, increased cycle times, and reduced throughput. The manual loading process also slows production.

Tridex Technology, a Glebar Company, has delivered a process using its SG series Burr-Free Electrochemical Surface Grinding Machines to form the slots on castle nuts while reducing scrap, improving cycle times, and increasing daily throughput.

“ECG provides fast, accurate, and burr-free results with no debris after rinsing, no metallurgical damage, and no distortion,” said Tom Travia, Director of Sales, ECG at Glebar. “The burr-free grind eliminates the need for deburring or other secondary operations, improving productivity and reducing scrap.”

In a recent test, Tridex used their SG-1645 Burr-Free Electrochemical NC/CNC Grinder to grind 0.165-in. slots into castle nuts. The grind resulted in a cycle time of 8.9 seconds, equating to 339 parts per hour, generating as much as a 70% savings in productivity.

An optional pallet index table allows full production without stopping to load and unload parts. For very high-volume parts, a custom dial index ECG machine can be built with three ECG spindles, so every cycle produces a finished part.