6 Best Alignment Shims For Rotating Equipment Precision

Precision alignment of rotating equipment is the difference between a machine that runs for decades and one that vibrates itself into an early grave. When the shafts of a motor and a pump are even slightly misaligned, bearings fail, seals leak, and energy consumption spikes. Choosing the right shim isn’t just about filling a gap; it is about maintaining structural integrity under high-torque conditions. The following guide breaks down the best options to ensure every alignment task is completed with professional-grade accuracy.

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Precision Brand Slotted Shims: Best Overall Kit

Precision Brand is the industry standard for a reason, offering kits that cover almost every common bolt size. These shims feature a slotted design that allows them to slide around bolts without requiring the hardware to be completely removed.

The primary advantage here is the consistent thickness tolerance. When dealing with critical tolerances, a shim that is labeled 0.050 inches but measures 0.053 inches ruins the entire calculation. Precision Brand maintains tight manufacturing standards, ensuring what is printed on the tab matches the actual metal.

For general maintenance crews and contractors who handle varied equipment, these kits are the gold standard. They eliminate the guesswork and keep the workspace organized.

VibrAlign re-align Shims: Top Pro-Grade Choice

VibrAlign understands that time is money during a shutdown. Their re-align shims are designed for speed, featuring a tabbed design that makes them easier to grab and position under a heavy motor base.

The material quality is superior, resisting the “crush” that can happen with lower-grade stainless steel over time. When a motor is torqued down, inferior shims might deform or lose their flatness, leading to a loss of the very alignment that was just achieved.

These are the preferred choice for high-speed rotating equipment where vibration is the enemy. Investing in these ensures that the alignment holds firm even under heavy load.

Accu-Size Shim Stock: Best for Custom Shapes

Sometimes, standard precut shims do not fit the odd footprint of an older or custom-built gearbox. This is where Accu-Size shim stock becomes necessary.

Having rolls or sheets of shim stock on hand allows for the fabrication of custom, oversized, or odd-shaped shims. This is vital when the machinery base plate has been modified or damaged by previous, improper installations.

Using shears to cut custom stock requires a steady hand and deburring tools. Always clean the edges after cutting to ensure there are no metal burrs that would prevent the motor foot from sitting perfectly flat.

SKF TMAS Series Shims: For Heavy-Duty Machinery

When moving into the realm of massive industrial turbines or heavy-duty pump sets, the SKF TMAS series is the go-to solution. These shims are designed to handle extreme compressive loads without deforming.

SKF provides excellent labeling and packaging, which helps in keeping track of the shim stack height during a complicated alignment process. Precision machinery often requires a mix of thicknesses, and SKF makes it easy to stack these securely.

Their durability is matched by their resistance to corrosive environments. If the equipment is located in a damp or chemical-heavy area, the high-grade stainless steel used in the TMAS series prevents rust-induced thickness loss.

Martin Slotted Shims: The Best Value Per Piece

For contractors managing large-scale jobs with dozens of motors to align, Martin Slotted Shims offer the best balance of cost and quality. They provide the necessary precision without the premium markup of specialized laser-alignment kits.

These shims are reliable and uniform, making them perfect for standard industrial applications. They come in convenient packs, allowing for easy replenishment of specific thicknesses that are used more frequently than others.

While they may lack some of the ergonomic tab designs found in more expensive brands, they get the job done correctly. They are an essential part of any well-stocked truck.

Lawton Shim-In-A-Can: Most Convenient Field Kit

The Lawton “Shim-In-A-Can” is exactly what it sounds like—a highly portable, durable container of precut shims. It is designed for field technicians who need to move quickly between job sites.

The physical container prevents the shims from getting bent, scratched, or lost in the bottom of a tool box. When you are on a roof or in a cramped mechanical room, having your entire shim inventory in one secure canister is a massive efficiency boost.

It prevents the frustration of showing up to a job only to find that the specific 0.020-inch shim needed is bent or missing. Convenience, in this case, directly translates to better equipment longevity.

Precut Shims vs. Shim Stock: Which Do You Need?

Precut shims are the first choice for 90% of alignment tasks. They save time, they are guaranteed to be flat, and they have pre-measured slots that fit standard bolt patterns perfectly.

Shim stock is a specialist’s tool intended for non-standard frames, unique bolt patterns, or situations where a specific thickness is required that does not exist in a precut kit. Using stock takes significantly longer because the material must be measured, cut, and deburred.

If you are doing routine maintenance, stick to the precut variety. Reserve the shim stock for unique, one-off engineering challenges where standard sizes simply will not work.

Stainless Steel vs. Brass: Picking Shim Material

Stainless steel is the industry standard for most machinery alignment. It is hard, resists corrosion, and maintains its thickness under high pressure.

Brass, while easier to cut and deburr, is significantly softer. It can compress or “flow” over time under the heavy load of a large electric motor, which will eventually throw your alignment out of spec.

Only reach for brass shims in low-load applications or when dealing with equipment where the soft metal acts as a sacrificial barrier to prevent damage to the machine frame. For almost everything else, stainless steel is the only correct choice.

Correcting Soft Foot: A Key Step in Alignment

Soft foot occurs when one of the motor’s feet does not sit firmly on the base, leaving a gap even when the bolts are tightened. If you ignore a soft foot, you are essentially trying to bend the motor base when you tighten the bolts.

To check for this, tighten all bolts and then loosen one while measuring with a dial indicator. If the indicator moves, you have a soft foot that must be shimmed before you even begin the primary shaft-to-shaft alignment.

Never try to “pull” the equipment down by overtightening the bolt. That creates internal stress that destroys bearings and shafts.

Reading Shim Sizes: How to Know the Thickness

Most professional shims are color-coded, but never rely solely on color if the paint has worn off or been obscured by oil. Always use a digital micrometer to verify the thickness of a shim before installing it.

If a shim has lost its label, measure it in the center, not near the edges where burrs or deformation might cause an inaccurate reading. Keeping a organized box with clear size dividers is the best way to prevent mix-ups.

Consistency is key. If you are stacking shims, try to use the minimum number of pieces possible. A stack of four thin shims is always less stable and more prone to error than one or two thicker, precision-ground shims.

Precision alignment is an exercise in patience and detail. By selecting the right materials and following rigorous installation steps, you can prevent expensive failures and extend the life of your equipment significantly. Stick to the proper tools, keep your inventory organized, and always account for soft foot before finalizing your alignment.