I've narrowed down my choices to these two. The automatic chain clamp on the hydraulic assist sounds like a nice touch, but if I understand correctly, the 511ax has a self centering clamp and the 109179 doesn't. Is this something you have to do with every chain? Or do you center the vice once and forget it? I will just be doing my own chains but intend to sharpen for others on a word of mouth basis. The automatic clamping may not be worth it to me if I have to dink around with the vice with every chain. Opinions?