Both fixed and attribute gages have their place in threading. Capital equipment and maintenance on that equipment are investments, not expenditures. Maybe every 20 pieces will go into the optical comparator so the operator can see a trend before it gets out of control. Check customer drawings, if they ve been provided. If the customer hasn t given a clearly defined specification, then get it formalized.
Ensure controls are in place throughout the production.
Make sure the first-offs go through complete and detailed inspection before go is pushed for the entire operation.