December 14, 2017
Do’s and Dont’s of Proper Shim and Tool Storage
By Tom Shelton
SHIM STORAGE & USAGE:
Shims are an integral part of obtaining precision shaft alignment in an efficient manner. Only new, clean shims should be used. The cost of new shims is minimal when compared to the cost of extra downtime caused by an inefficient precision alignment process. Proper choice, use and storage of shims is critical to obtaining a precision machine alignment.
Improper storage and re-use of old shim stock can be a contributing factor to soft foot. Dirt, debris, bent shims and inconsistent thickness of cheap carbon steel shims can drive up costs in lost time as the frustrated mechanic struggles with alignment problems created by “trying to save a couple of dollars.” The old saying “Step over a dollar to get to a dime” comes to mind.
Shims selected for a given alignment should be the correct and same size. Shims should be made of stainless steel, a material that can withstand the compression created by the motor mass and clamping force of the hold down bolts.
When selecting the proper shim size choose the size shim (A, B, C, D, etc.) that offers the most contact between the foot and base and has the proper slot size for clearance around the hold down bolts of the movable machine. Never combine multiple shim sizes or materials in the same stack of shims.
Be mindful of the position of your shim stack in relation to the bolt. Keep clearance between the shim and the bolt to prevent damage to the shim stack (bent shim) or bolt threads. A bent shim can induce soft foot where soft foot does not actually exist.
Although precision measuring equipment is typically made for industrial settings, it should be handled with care. Keep precision tools in their original case. Environmental effects from improper long-term storage can be detrimental to precision alignment equipment. Proper care and routine maintenance are required. Calibration should be performed annually or every other year at a minimum.
Casually throwing dial indicator sets into a box or drawer can damage mounting brackets and the dial indicators can develop hysteresis (internal friction). They should be stored in their protective cases.
Laser Shaft Alignment systems should be properly maintained for optimal performance. Dirty sensors (laser and detector lens) can lead to non-repeatable measurement results. All system components should be stored properly in the carry case to prevent damage to said components.