Hello Warren:
Thank you for the kind words and I am glad you enjoy my posts. While no medical textbooks discuss Old Iron Disease, it is a benign condition (rather than 'disease', 'ailment', or 'afflication'). Old Iron Disease can be said to be a form of addiction that usually has constructive and positive outcomes for the person developing it, as well as for family, friends, and surrounding community. A manifestation of Old Iron Disease is often the need for finding out the past history of tools and machinery acquired or at least investigated by the person having Old Iron Disease.
In short, you have all the classic symptoms of what most of us have been enjoying ( a fair word, I think), for years, if not most of our lives.
A buddy of mine put it succinctly: He likes to pick up old tools, even when he has multiples of them. When he holds the old tools, even if he does not know the history of the tool, he says he feels something of the previous owners/users of those tools. My way of putting it is: "I wish those old tools could talk".
You came up with an excellent application for the incline level in the setup and use of the portable boring bar. As you note, working out on a jobsite to line-bore excavator buckets and booms, linkages, etc is a place where there is no solid reference surface to setup off of. I would think your incline level is actually a bit too fine and too nice of an instrument to schlepp out onto a jobsite for work that does not require its degree of accuracy. You may well find yourself "chasing your tail", a saying I use when working with an instrument having too fine a resolution for rough conditions.
An example of an 'inclined level' situation occurred a few years back at Hanford Mills Museum. We had erected their horizontal steam engine, an 10" x 12" center crank engine. To get one flywheel to line up with an existing line shaft for belting up the engine to the mill's line shafting, I had designed an extension to the crankshaft. This required an outboard pedestal bearing. There was an existing mortared stone bearing pedestal from the original side-crank engine (removed many years prior), and we mounted the outboard pedestal bearing on it. Things lined up nicely, or so it seemed, and the engine turned over freely. I had levelled the mainframe of the engine off the crosshead guides using Starrett 98 levels, 1-2-3 blocks, and long matched parallels. I levelled off the split joint of the pillow block bearing we used for the outboard pedestal bearing. We soon started up the engine on steam. That is when we got a mild surprise: the outboard pedestal bearing and the inboard engine main bearing began to warm up more than I liked, whilst the further engine main bearing still ran cool. I had set the clearances on all three bearings fairly loose, since this was a startup, figuring I could tighten the clearances once the journals 'bedded in' to the bearings. Despite this and a good levelling of the engine and outboard bearing, I was feeling bearings heating up. That led me to breaking out my Starrett 696, known as a 'crankshaft strain gauge'. I had last used that instrument perhaps 30 years earlier on Fairbanks-Morse diesel engine ( OP 38 D 8 1/8 series) crankshafts in Venezuela to check generator tail bearing alignments. The 696 strain gauge told the tale: the crankshaft bearings and pedestal bearing were in alignment at 9:00 & 3:00, and out a good bit at 6:00 to 12:00. That being established, I used my 98 level's base groove and cross vial by putting the level right on the extension of the crankshaft. This showed the crankshaft had a slight incline to it, somewhere between 1/32" and 1/16" in maybe 6 feet. This was time for some head scratching and then the realization hit me: whomever had last rebabbitted the engine's main bearings (some time prior to about 1930), had line bored them but had not setup the boring bar so that its centerline was in plane with am imaginary line across the crosshead guides (cast into the mainframe like the ways of a lathe). The bottom of the engine mainframe was never planed off, and was a rough casting. The engine had last been used in a marble quarry, somewhere in Vermont, and last ran about 1930. There is no telling what kind of foundation it was on, no telling how level the frame of the engine was, nor how the bearings were rebabbitted. Someone could simply have 'smoked' the crankshaft main journals with soot, blocked the crankshaft to what seemed like correct centerline, and poured the babbitt. No line boring done afterwards, maybe a cleanup with a scraper.
The Old Iron Disease in me was imagining all sorts of things, none of which would solve the immediate situation Speculation as to how the bearings were rebabbitted was getting us nowhere. Rather than beat the issue to death, I figured the only thing to do was to live with the main bearings running on an incline, and 'cheat in' the outboard pedestal bearing. Some shims under one side of the pedestal bearing and some scraping of the babbitt to match the incline a bit better, and we solved the matter.
I used the graduations on the vial of my 98 level to determine the 'pitch' or inclination of the crankshaft to level, and matched that pitch with my level on the split joint surface of the pedestal bearing.
What it came down to was this: I was erecting a steam engine with a degree of accuracy used for machine tools and powerplant turbines. An old boss of mine used to sum this sort of thing up rather eloquently, though off-color, referring to this sort of thing as "picking fly shit out of the pepper with boxing gloves on". My old boss was a man who'd come up the hard way. He started out working as a 'pile buck' on a crew driving pilings. About as rough a work as you can find. He went to college part time and eventually got his engineering degree. He and I worked on hydroelectric plant construction projects, and his time as a pile buck served him well. He knew what field conditions were vs what theoretical engineers were asking for.
Your inclined level is a fine instrument, for sure. As I wrote in my previous post, I think its purpose was to level machinery and machinery foundations using a given incline as a plane of reference. It would be a bit of a challenge to use it to measure the pre-existing incline of surfaces relative to level. I'd oil the machined surfaces of the level and put it in a good safe spot such as the drawer of a machinist chest or a wood case. Like my 696 crankshaft strain gauge, your inclined level may be one of those instruments that you would think you will never use.... and then out of the blue some job comes along where it is the very thing needed.
There is an other timeless saying: "Dead Men tell no tales". We who have somewhat advanced cases of Old Iron Disease tend to differ with that opinion, as Dead Men, though otherwise anonymous, often speak to us through their tools and machinery, making us something of their continuum.