Underwater Propeller Change,
USS Enterprise, CVN-65

Cutting the Boss Nut

Cutting the boss nut began 10 June 1983 and the depth of 30 feet with the water temperature of 59 degrees Fahrenheit. Underwater visibility was limited to a maximum of 12 inches.

The first cut was made in the boss nut keyway at the nine o'clock position (facing forward) which required the divers to cut from a left-hand position. Divers began initial rough cutting along the after face of the boss nut starting from the outer beveled edge and at the key way and working inward towards the shaft threads. Care was taken not to get closer than one inch to the shaft threads during the rough cutting. The diver would then start his next rough cut, deepened until the final pass reached within one inch of the propeller hub. Roughed out, the initial kerf extended from the after face of the nut to within one inch of the propeller hub, and that a depth of approximately 4 inches.

Progress on the first day was slow as divers experimented and cut with exceptional care. Divers noted that slag built up more quickly during the underwater cutting than during surface cutting operations. A pneumatic chipper was required to remove the slag before inspecting progress. For most cutting, divers achieved the best result by directing a freshwater hose jets near the curve to flush away slag and gases and improve visibility of the kerf.

Divers also learned that if they attempted to cut too fast or borough to deeply into the metal while rough cutting with the Kerie Cable, a small explosion or blowback would occur. To overcome this problem, divers had to refine their technique to avoid cutting too fast or gouging out large bites.

The second day of cutting commenced on the one inch portion remaining at the forward face of the boss nut. The first cut was smooth and to a width of approximately 2 1/2 inches (the keyway width) and trenched to a depth of five inches. Hydraulic jacks were then test fitted and found to require approximately one-half inch shims. The shaft was then jacked over to align another keyway selected for the second cut in a 12 o'clock position. This position was relatively easy to work in because it afforded good visibility and because all gas was invented straight up. The second cut was completed in only four hours and 50 minutes, a substantial reduction in time over the first cut. The second kerf was then dressed up as smooth as possible. With kerf one and kerf two now dressed up, eye bolts were installed in each half of the boss nut. Two hydraulic jacks with shims were put in each cut. The first attempt was made to break the nut with pressure reaching 12,000 PSI. The boss nut did not break.

The third workday began with another attempt to break the boss nut, but to problems arose with the hydraulic jacks The jacks were sensitive to uneven surfaces and would jam when cocked and consequently would not compress to permit repositioning. As a result of increasing the pressure, the seals were damaged and the jacks started to leak and were rendered unusable. All jacks were then removed and it was decided to install only two jacks in kerf No. 1.

WebMaster Bruce