Soft-Foot Measurement and Correction Shim

Because a machine that rocks changes shape when the bolts come down. Loosen one foot with an indicator on it and watch what moves: if the foot springs up, the bolt was pulling the machine down onto a gap and distorting the frame, and the shim to add is exactly the rise measured. Working ONE foot at a time with the other three tight is what isolates each one, and repeating the whole sweep matters because correcting one foot redistributes the others. Two kinds hide behind the same reading. Parallel soft foot is a plain gap and takes a flat shim. Angular soft foot is a foot that is not parallel to the base and takes a stepped or machined shim -- a flat shim under an angular foot only moves the contact point and can make the reading worse. The diagonal check is what separates a bad foot from a bad base: four feet reading 1, 7, 2 and 1 mils give diagonals of 2 and 9, disagreeing by 7, and the whole disagreement sits on the one foot reading 7. A twisted base instead shows the rise spread across a diagonal pair. Shim the bad foot and sweep all four again. Aligning a machine before that shim goes in produces a beautiful set of cold readings that change the moment the bolts are torqued, which is why this comes first and not last. This reads the indicator numbers the user takes. It does not distinguish parallel from angular soft foot by measurement -- that needs a feeler gauge under the foot at several points, or a step check, and the pattern reported here is an indication and not a determination. It does not evaluate the base, grout, or anchor bolts, a cracked or voided grout being a common root cause that shimming will not fix; it does not address bolt torque or the bolt-bound condition where a machine cannot be moved horizontally without drilling; and it does not check pipe strain, which produces the same symptom and is not cured by shims. The machine manufacturer's mounting requirements and the plant's precision maintenance procedure govern.

the rise measured at a foot when that foot alone is loosened, with the other three tight, is the shim that foot needs; the two diagonal sums are compared to separate a single bad foot from a twisted base.

The soft-foot sweep as standard precision maintenance practice, by name. The 0.002 in (0.05 mm) acceptance figure is common practice and is ENTERED rather than fixed. The machine manufacturer's mounting requirements and the plant's precision maintenance procedure govern.

Reading four indicator numbers the millwright takes; no manufacturer table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: foot_lf_in, foot_rf_in, foot_lr_in, foot_rr_in, threshold_in, worst_foot_rise_in, failing_feet, diagonal_lf_rr_in, diagonal_rf_lr_in, diagonal_difference_in

• Parallel versus angular is an indication, not a determination that needs a feeler gauge or a step checkmillwright practice
• Grout, base and anchor bolts are not evaluated voided grout is a common root cause shimming will not fixmillwright practice
• Pipe strain produces the same symptom and is not cured by shimsmillwright practice