Advanced Metalworking Solutions for
Naval Systems that Go in Harm's Way

Main Propulsion Shaft Taper Inspection

NMC is developing a white light scanning system for inspecting tapers of main propulsion shafts. The project is expected to save ship construction and maintenance costs. NMC photo


This NMC project is evaluating and developing white light scanning technology for inspecting submarine and aircraft carrier shaft tapers. This will eliminate the labor-intensive use of costly single-purpose gauges and replace them with less costly systems that allow for more rapid inspections.


Power is applied to submarine and aircraft carrier main propulsion shafts through a tapered connection between the shaft and the inboard coupling. To prevent mismatch, tapers are inspected using taper ring and plug gauges that are heavy and cumbersome. Each taper requires from six to 10 inspections as the taper is carefully shaped to the correct contour. Eight work shifts and up to 66 labor hours can be saved if these gauge inspections are eliminated. In addition, taper gauges cost $615K per set and must be refurbished every three years at a cost of $70K. Separate gauges must be used for every ship class.

Technical Approach

The project team is working with industry to identify the most promising white light scanning system, developing a prototype for shipyard use, and optimizing the prototype in response to testing and evaluation.


The four naval shipyards (Portsmouth, Norfolk, Puget Sound, and Pearl Harbor) will see a cost savings of over $5M just by eliminating the purchase of the VCS taper gauges. They will see an additional cost savings of $900K per year by eliminating the need to maintain the existing taper gauges. The labor to perform the inspections will be reduced by eliminating the lifting and handling process and by reducing the time required to perform taper inspections. Employee safety will benefit from eliminating the repeated lifting and handling of 750-pound gauges.


Implementation will occur in the second quarter of FY14 as Norfolk Naval Shipyard uses the prototype system delivered to them for evaluation. The other Navy shaft refurbishment facilities will also implement the results as the Navy eliminates the current gauge process.




Kurt Doehnert


Naval Sea Systems Command (NAVSEA)
Naval Surface Warfare Center, Carderock Division
Norfolk Naval Shipyard
Portsmouth Naval Shipyard
Pearl Harbor Naval Shipyard
Puget Sound Naval Shipyard