Sewing Machine Adjustment Tolerances

[jfhspike]

I've got a Bernina 217 that I got from a friend who could never get it to sew right, and I'm now starting to work my way through the "adjuster's manual" to try to get it working a bit better (and doing some cleaning, oiling, etc. along the way).

The manual says things like "The needle must enter the middle of the stitch hold see from front-to-back" (i.e., it should be the same distance from the "feed" side, or "operator side" as it is from the "exit side").

I understand what this means, and how to adjust it, but what I don't know is the tolerance: should I be making these distances match with feeler gauges or a micrometer depth gauge or calipers, and worrying about .001" adjustments, or is .01", which I can see with a good eyeballing, good enough?

(It's pretty obvious that something is terribly wrong with at least the bobbin/hook timing adjustment, because when I set the needle to far-left, it hits the bobbin case rather than slipping down into the cutaway part the way that it's supposed to. But right now I'm at a step 1, which is the needle stitch-hole adjustments).

Once again, thanks in advance for any advice you have. My new dinghy spritsail will appreciate it.