Re: 0-80 thread measurement
Bob is 100% right. Threads (or gears) and cheap don't mix.
Caution about ring gages:
A) They are what drove me to Johnson Gage to begin with as they are a composite gage that do not detect conditions that can (and did) result in a customer concern.
B) They can be very tricky to set to the masters because they are so dependent upon touch and feel time-to-time and inspector-to-inspector.
My experience was that when 'best' set, both GO and NO-GO artificially rejected parts that were, in truth, fully conforming (up to about 14% of production). When the rings were set to pass most OK product, they also passed non-conforming product on to the customer.
Another option would be optical scanning. Johnson may be willing or know of another source who you could 'job out' this as both a means to verify the ring gage 'best' set and to satisfy your customer concern for sufficient thread form analysis. It could be a compromise that is financially acceptable to your company but minimizes your risk.