Hi Thomas,

That was an interesting analogy that you tried to put forward "selective assembly" (SA). I also read through the linked document. I feel there is a minor variation in the generally accepted concept as has been discussed in the document.

SA, in specific applies to cases where the combined tolerance of two mated parts [or] relative tolerance between two mating parts must be within a very tight regime. Addition of shims to achieve the required fit normally does not come under this case as has been mentioned in the document.

However the other example of vane inserts inside a rotor body is very correct. The downside of SA is that it increases the spares inventory overhead. Suppose a rotor has three vanes that are selectively assembled and a vane fails. Instead of replacing the failed vane alone, one would be forced to change the whole rotor assembly, as it is impractical to order out a single vane with specific tolerances! In our hydraulic industry, this SA is very common - rotor+vanes, spool+housings, poppets+seats...

Answering Prahlad, I would feel that for one off or low volume production items it is a safe bet to use 0.1% resistors and be done with it. Selecting from a 1% batch brings another variable into the scheme - the accuracy of the DMM that is used. And then the TC is always there to play its part. Reason why I have long back stopped doing signal conditioners - best bought from a reliable source with a Cal. Certificate. The client is also satisfied.

Raghu