@Degen OK, this is becoming painful again. I'm going to tap out soon. Please re-read the first sentence of my post #94.
I have already stated for the sake of this simplified example that the bed is not twisted. So just set that aside...
So where am I telling anyone to start with a twisted bed & immediately start evaluating HS twist? By writing that sentence I mean both in the physical sense (the lathe has been pre-levelled) and in the geometric model sense (assume lathe bed plane is flat and HS is aligned to it). So you are preaching to the choir. I said both misalignment modes potentially contribute to the condition of taper and they both need to be checked off the list.
What your methodology still fails to address is this. Your lathe is first levelled (un-twisted) to the best your ability which is ALWAYS the way we should start out. We agree on that & always have. And it cuts a taper. So what do you do? You twist it & re-assess the coupon. It is now no longer level, it is now twisted to some extent. It still cuts a taper, so you twist some more, hopefully converging. If it does eventually cut a cylinder, happy you. But what if you reach a point where it still cuts a taper & the bed is slowly becoming a pretzel with increased jacking? If you repeat this 10 times, is that the point it might occur to you that there may be another factor like HS alignment and any amount of additional twisting may be futile? And maybe that singular HS adjustment removes all that TS jacking & you discover it wasn't even necessary to begin with? Now who has a bucket of swarf & is chasing their tail? I appreciate you wanting to save my time, but you are making some assumptions you cant back up. You 'assume' the HS wont move 'much' on a bolt-on lathe. Really? Those words made a problem disappear? Wouldn't it be better to measure HS yaw somehow if possible? How would YOU propose to measure it? Because you've already exhausted the taper evaluation measurement. Its a silly hypothetical example, but hopefully you get what I'm driving at.
I'm getting a vibe you think I'm perched on a high pedestal dictating useless trivia & afraid to get my hands dirty. I've digested the conventional mantra. I own a Starrett level & used it. I've adjusted my feet. I've also been in the back of my lathe, its how I was able to include pictures of the undocumented adjustment screws. My lathe is pretty good for my purposes but that's not the point. The only reason I've bothered to step back & think about this some more is to try & quantify the potential significance of HS yaw. Yes, its of academic interest if you want to use that word. So is having a map or GPS before heading down the road in the wrong direction.
