I do not expect everyone to agree with me on this subject, however, I felt that it was worthwhile to set my thoughts regarding leveling of Lucas boring mills with Laser equipment to paper to provide a 'counterpoint' to the general rush of the industry towards 'high tech' leveling.
I do not feel that a Laser should be used ALONE to level a Lucas boring mill. Using a Laser cannot only be misleading - it can also result in an improper machine installation.
There is nothing wrong with using a Laser after machine installation and final leveling is completed with a precision spirit level as described in Lucas literature to get an excellent permanent record of the machine geometry. The permanent record will allow you to use the Laser at a later point in time to see if anything has changed and is much faster to use than a spirit level.
The machines were not built using a Laser during the original grinding processes. The Saddles of the machines were intentionally ground with the outer ends lower than the centers. This was done so that the eccentric Saddle Outer Support Rollers could used to slightly raise the ends of the Saddle. The desired effect was to have a small, positive amount of mechanical pressure on the rollers at all positions of the Table on the Saddle. It was also recognized that there was no mechanism to lower the Saddle ends if they were too high - so they were always made either 'low or 'flat'. While there were definite tolerances to the amount that the Saddle ends could be 'low' and still consider the Saddle to be properly ground, not all Saddles may have their ends lifted up to a perfect straight line without distorting the Saddle casting. If you were to support a Saddle at the ends alone, it still might not 'sag' in the center into a perfectly flat condition. Of course, when the Saddle is on the Bed, you can 'force' the ends up by applying as much roller pressure as needed, however, the center of the Saddle may no longer be in contact with the tops of the center Bed ways. The Saddle Support Gibs will also have excessive pressure to the lower side of the Bed ways.
The machines were built to carefully defined tolerances with analog instrumentation. When using analog instruments, there is a natural, human tendency to 'quit adjusting' as soon as the instrument readings are inside the tolerance limit stated in the test package. There is also a very natural, human tendency when using a digital instrument to 'make the reading zero' - simply because you CAN, and simply because 'It must be better' that way.
The fact is the machine was built with each individual subassembly built within the stated tolerances using analog instrumentation, however, each subassembly was 'favored' to one side of the tolerance limit or the other depending on the readings from the mating subassemblies. In other words a Saddle that was being 'married' to a 'plus' Bed would be 'favored' to the 'minus' side of the tolerance so that the tolerances would not 'stack up'. By using a Laser and setting the described Bed to zero, then adjusting the described Saddle to zero, you will find that the Table assembly will not be found to be within tolerance. You have successfully 'pushed' all of the tolerance 'stack up' to the last part and there is nothing to adjust - you must re-machine and hand scrape to get 'good numbers'. What a pity, when there may be nothing wrong except a lack of understanding!
A spirit level will allow you more easily see when the entire foundation upon which the machine rests is 'rolling' in the earth while the machine is actually remaining flat and square (flat & square is what you really want). A Laser may allow you to see this depending upon how and where it is fixtured, however, it is very common that the readings are misinterpreted and the machine is 'leveled' until the Laser readings are zero without actually looking for non-machine deflection. This frequently results in the Saddle being 'Gull Winged' and way and gib wear being rapidly accelerated.
If the ends of the Saddle are higher than they were when the Table was scraped to the cross-travel ways, the Table will no longer contact the Saddle Top Ways properly. The Table will likely be contacting the Saddle only at the extreme ends. It may move easily when empty or lightly loaded, however, it will become extremely difficult to move the Table when carrying heavy loads and the Table may completely 'lock up' is you load the machine to near its weight capacity. Additionally, you will have a great amount of difficulty in cutting without chatter, since you will be machining parts that are - effectively - mounted to the center of a spring. Worse yet, if you run the machine for any great period of time 'leveled' like this, you will prematurely wear the bottom of the Table on the contacting ends alone. When the leveling error is finally corrected, the Table will still not contact the Saddle properly. Now it will be only in center contact since the ends are 'worn away'.
There is NOTHING 'wrong' with a Laser, however, it is actually much more difficult to use when leveling a Lucas boring mill than using a precision spirit level. The Laser, however, appears to be easier to use since you have a nice digital readout to gaze upon and you may only need one 'setup' to do the entire machine. The Laser, however, also makes it much easier to misadjust the machine. It’s a tool - it's not 'magic' and if you use it wrong it can really mess up your machine!