Chapter 36, Problem 39QTP

To determine

A manufacturer is ring rolling ball-bearing races shown in fig 13.15a. The inner surface has a surface roughness specification of 0.10 ± 0.006$\mu m$. Measured values taken from rolled rings indicate a mean roughness of 0.112$\mu m$, with a standard deviation of 0.02$\mu m$. Fifty thousand rings per month are manufactured, and the cost of rejecting a defective ring is $10.00. It is known that by changing lubricants to a special emulsion, the mean roughness could be made essentially equal to the design specification. Determine the additional cost per month that can be justified for the lubricant.