Baseplate tolerances, such as cited in ANSI/ASA Alignment S2.75-2017, specify that a baseplate must be level to <10 mils/ft, coplanar to <2 mils and each foot must be flat to <5mils. The machinist precision level is typically specified to be 0.5 mils per 12”. Automatically, it is assumed that this is sufficient for baseplate installation because the 0.5” per 12” is of a higher resolution than the tolerance.
If you had a granite surface plate, then the machinist level would absolutely work as the entire surface is dead flat and coplanar. You can place the level at any point of the granite surface and assuming that you keep the same orientation, you will get identical bubble readings on the bubble level.
Unfortunately, baseplates are not entirely flat. Depending on where you place the machinist level, you will get entirely different readings. The warp on the baseplate gets magnified by the mounting points, methods of attachment and the weight of the baseplate causing warp from gravity.
Fortunately, there is a field-proven solution to make sure the baseplate is flat and level. The Easy-Laser XT770G, the complete rotating equipment alignment commissioning package, includes the D22 rotating laser.
The laser projects a perfect 263-foot laser plane with a detector that has 0.1 mils resolution. This is far greater than the 12” range of the machinist level. In general, this allows the base to be leveled to 0.02 mils/” and coplanar to under 0.5 mils. Machinist levels can’t ensure that surfaces are coplanar, as shown in the photo below:
A laser works like a high precision straight edge, allowing for such surfaces to be measured all at once.
In the same way it has made shaft alignment easy and accurate, flatness and level measurements can also be taken by the same installation crew prior to alignment. The measurements can be taken, flatness corrected and documented using the same computer that will be used for the shaft alignment task.
Our Easy-Laser XT Series is the only laser alignment platform on the market today with the new ANSI alignment tolerances built-in giving the user the freedom to choose between traditional tolerances, the new ANSI standards, or custom tolerances.
Alignment by Daus Studenberg CRL