kaldi61 wrote:Yes, zero is where burrs lock up. oldNuc said it best.

Generally, Zero is where the burrs first rub. Ideally the burrs should rub uniformly around at this point but nothings perfect. This is how mine is at least after adjusting the screw tension to align the shaft.

I think that may be the true definition of zero, as it is the tightest grinding setting possible.

As we are using the 'zero' as a reference point to reproducibly gauge grinder setting and make adjustments relative to that 'zero', as long as you are consistent, it doesn't matter which you use. I find it easiest to use the locked burr position. If I forget my 'zero' I simply tighten the burr all the way, and that's my reference point.