Page "Diamond turning" Paragraph 48

The SPDT manufacturing process produces a relatively high percentage of defective parts, which must be discarded.

As a result, the manufacturing costs are high compared to conventional polishing methods.

Even with the relatively high volume of optical components manufactured using the SPDT process, this process cannot be classified as mass production, especially when compared with production of polished optics.

Each diamond-turned optical element is manufactured on an individual basis with extensive manual labor.