I knew I didn't explain that well.
You've got it basically right.
Yes, once the pin is seated in the numbered ring, assuming that the ring and the washer below it are seated correctly, the tensioner will only turn so much left to right. Ideally, this will line up with the numbers 0 - 9, but sometimes doesn't and because it's arbitrary, it's almost not of concern - except to the end user.
Once you disengage the pin on the silver knob from the ring, you can spin the ring to change where the numbers are, but the adjustment range stays effectively the same. This is mainly a change of perspective but it's also good for fine tuning. This is good for a "small" tension discrepancy because at most, this adjustment will turn the knob up or down the post a small bit of the thread more or less than before.
If you disengage the pin and turn the silver knob instead, you're moving the knob, and consequently the whole mechanism further from the base of the tensioner or closer to it, effectively changing how tight the tensioner is a 0 and all the way up the scale. This is more of a coarse adjustment. Once you've made this adjustment, you'll want to make the other adjustment (to the numbers) to make it sane again. This is a step that can sometimes be done without taking the tensioner right down to its component pieces to rectify a larger issue with tension, like the one that mpeters1200 is experiencing, assuming that the tensioner is assembled right, but adjusted wrong. This can adjust something as much as several numbers worth of "wrong" - Say tension is right at 9, or 0, but wrong in the middle and opposite ends. This is because you're turning the knob a thread or even several threads up or down before seating that pin again.
If it's assembled wrong, of course it has to be taken apart.
Here's the "Why"
When you reassemble the tensioner, you turn the knob onto the post a number of turns, then seat the pin into one of the holes.
How many turns before you seat it? It's not written in any manual, you just turn til it "feels" like you should seat it, right?
This is where the "mis-adjustment" comes in. If the person doing the adjustment just leaves it there, or maybe puts the numbers at some sane spot and leaves it, there's a good chance the tension will be wrong.
No, I don't have a set number of turns when I reassemble one, I turn it til it feels right, then test it to see what the tension is like. If the tension range is wrong, I push the ring in, so the pin clears it, and turn the knob right or left, depending on the results of testing, then I fine tune by adjusting the numbers.
What testing?
At 0, with the presser foot down, there should be a barely perceptible amount of tension on the thread. It should be almost the same as the presser foot being up. Turn it to 1, and there should be noticeable drag. By about 3 or 4, the needle should deflect some (about a 1/16") before the thread starts to come out more. (This is all in the link I posted btw.
http://www.archaicarcane.com/fragile...-equal-stress/ )
If this is not how the tensioner behaves, it has been mis-adjusted the last time it was taken apart, it's missing pieces, was assembled wrong, or needs servicing.
Did I make anymore sense this time, or did I just muddy up the waters more?