Shims are used in the shaft alignment process to correct the vertical position of a movable machine so it will be in alignment with the stationary or reference machine.
After a dial indicator or laser shaft alignment tool is used to measure the misalignment of the two machine’s rotational centerlines, shims are added or removed (as indicated by the alignment tool) from the moveable machine’s feet to correct the vertical angularity and offset.
Shim material can be cut from brass or stainless steel shim stock; however this process is very labor intensive and time consuming. Also, when cutting shims from stock the sharp burrs can be a safety issue as well as creating errors in the “stack up” of the shims.
The best solution is to use Precut Stainless Steel Shims. These shim kits have been in use for decades and are an invaluable tool for the mechanic preforming alignments. Plus precut shims have safety tabs to grab when placing under the machine feet as well as having rounded edges without burrs, reducing safety issues associated with shims cut from stock.
Precut Stainless Steel Shim Kits are typically available for machine foot sizes 2″x 2″, 3″x 3″, 4″x 4″, 5″ x 5″ in thickness from .001″ to .005″, .010″, .015″, .020″, .025″, .050″, .075″, .100″, and .125″. Other sizes and thickness are available from various manufactures as are metric shims used in the Wind Turbine industry.
Precut Stainless Steel Shims are a cold rolled steel product with precise thicknesses, however shims .050″ and thicker are rolled to a nominal thickness and can vary in thickness by +/- .005″ dependent upon the manufacture. Some manufactures mark their thicker shims with both the nominal and actual thickness. Thicker shims that are not marked with the actual thickness will need to be measured with a micrometer or vernier caliper during the shaft alignment process.
When using shims during the shaft alignment process it’s a good idea to limit the number of shims to 5 or less under the machine feet. Consolidate shims as much as possible as a large stack of thin shims can induce a soft foot.
