6 Best Precision Shims For Shaft Leveling Worth Using

Precision leveling is the difference between a machine that runs for decades and one that vibrates itself into an early grave. Whether installing heavy HVAC units on a commercial roof or setting industrial blowers on steel frames, proper shaft alignment relies entirely on the quality of the shim beneath the foot. Relying on makeshift scraps of tin or rusted washers is a recipe for premature bearing failure and costly maintenance cycles. High-quality precision shims provide the repeatable, load-bearing support necessary for long-term structural integrity.

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Precision Brand Slotted Shims: Best for Versatility

Precision Brand slotted shims serve as the industry standard for a reason. These shims feature a wide, open slot that allows for easy placement around existing anchor bolts without the need to fully remove hardware.

The primary advantage here is efficiency during the iterative leveling process. When adjustments require adding or removing thickness, the slotted design allows for quick swapping, saving significant labor time on the job site.

Consider these for any standard installation where bolt clearance is not an issue. They handle high compression loads without deforming, ensuring the machine foot stays locked at the exact required elevation.

Accu-Shim Pre-Cut Stainless Shims: Top Durability

Corrosion resistance is mandatory in exterior environments, especially on flat roofing systems exposed to fluctuating humidity and rain. Accu-Shim pre-cut stainless shims are crafted from 300-series stainless steel, which resists rust far better than standard carbon steel alternatives.

For an HVAC unit or a pump mounted on a rooftop curb, standard steel shims can oxidize rapidly, potentially seizing to the base and making future adjustments impossible. Stainless steel prevents this binding, ensuring that a shim installed today can be removed five years from now without a struggle.

These shims maintain their structural geometry under heavy load. If the application involves high-vibration equipment, count on these to hold their thickness without “creeping” or thinning over time.

Martin Accu-Taper Shims: For Precise Tapered Fits

Rarely is a mounting surface perfectly parallel to the machine foot. When the base and the foundation are slightly out of plane, a flat shim will create a stress riser, causing the machine to rock or distort when tightened.

Martin Accu-Taper shims solve this by providing a controlled, gradual incline. This allows the shim to seat flush against both the irregular concrete surface and the flat machine foot, effectively eliminating the gap that causes mechanical stress.

Use these when dealing with rough-poured concrete pads or warped steel mounting plates. Trying to force a flat shim into an angled gap is a professional error that leads to uneven load distribution and cracked machine casings.

Sim-Pull Slotted Shim Kit: Best All-in-One Field Kit

Field work demands organization, and the Sim-Pull Slotted Shim Kit addresses the chaotic nature of job-site adjustments. These kits package a range of thicknesses in a single, transportable case, ensuring the right shim is always within reach.

The “Sim-Pull” design often incorporates tabs that make extracting a specific shim from a stack easier. This is a massive benefit when fingers are cold or gloved, preventing the frustration of trying to pry thin metal sheets apart with a screwdriver.

Invest in a comprehensive kit if the project involves multi-machine installs or frequent maintenance checks. Having a full spectrum of sizes prevents the temptation to “double up” on thinner shims, which creates an unstable foundation.

Lawton Standard Products Shim Stock: For Custom Jobs

Sometimes the required shape is irregular, or a specific shim size does not exist in a pre-cut format. Lawton Standard Products shim stock allows for the creation of custom-fit shims using basic tin snips or a bench shear.

This approach is best for custom fabrication or specialized equipment where standard bolt patterns do not apply. Keep a roll of assorted thicknesses on the truck to handle unexpected gaps that pre-cut shims cannot fill.

When cutting custom shims, always deburr the edges with a file before installation. Sharp, raw edges can slice into the coating of a machine base or create an uneven contact point that compromises the level.

MY-SHIM Color-Coded Plastic Shims: For Easy Sizing

Plastic shims serve a specific purpose in vibration-dampening applications and non-conductive setups. MY-SHIM products utilize color coding to denote thickness, which drastically reduces the time spent measuring stacks with calipers.

In a fast-paced environment, looking at a stack and seeing three blue shims and one yellow is significantly faster than checking every single piece of metal. These are non-corrosive and generally resilient against mild chemical spills, making them suitable for pump rooms or equipment enclosures.

Avoid using these if the clamping load is extreme, as plastic can cold-flow under excessive pressure. Use them for leveling light-to-medium-duty equipment where non-conductive properties provide an extra layer of safety.

Shim Materials: Stainless Steel Brass or Plastic?

Choosing the material is just as important as choosing the brand. Stainless steel remains the king of longevity and heavy loads, providing a reliable, non-compressible interface between the machine and the foundation.

Brass shims offer a softer alternative, which can be useful when you need the material to “give” slightly to accommodate a slightly uneven mating surface. However, brass can oxidize in wet, outdoor roofing environments if not protected.

Plastic shims are strictly for low-load applications where vibration dampening or electrical isolation is the primary goal. Never mix materials in the same stack; different hardness levels will result in uneven compression and a return to the leveling issues you were trying to solve.

Correcting Soft Foot: A Shimming Best Practice

“Soft foot” is a condition where one machine foot does not make solid contact with the mounting plate, leading to frame distortion when the bolt is tightened. This is common on rooftops where the support steel may have deflected during construction.

To correct this, loosen all foundation bolts and use a feeler gauge to measure the gap under each foot. Only after identifying the gap size should a shim be inserted; never assume that forcing a bolt down will flatten the machine.

When done correctly, the machine should sit perfectly flat on the shims without any strain on the frame. If the frame flexes even slightly when the bolts are torqued, add more shims until the “bounce” disappears.

How to Properly Stack and Install Precision Shims

Professional practice dictates using the fewest number of shims possible in a single stack. A stack of four thick shims is infinitely more stable than a stack of twelve thin ones.

Always place the largest shim at the bottom of the stack to provide a stable base, layering smaller shims toward the top if necessary. Ensure the slot of the shim is oriented away from the direction of the load or vibration to prevent shifting.

After tightening, always re-check the alignment with a laser or dial indicator. Shimming is an iterative process; it is rarely perfect on the first attempt, and precision tools are the only way to confirm success.

Pre-Cut Shims vs. Shim Stock: Which Do You Need?

Pre-cut shims are the go-to for professional contractors who value time and repeatability. They offer known thicknesses, consistent dimensions, and an immediate start to the installation process.

Shim stock is a contingency tool for the “impossible” job. Use it when the machine footprint is non-standard or when a specific, rare gap must be filled.

Stocking both in the tool crib creates the most resilient operation. Rely on the pre-cut shims for 90% of the work, and keep the roll of shim stock for those odd-ball situations that would otherwise stall a project for days.

Effective shimming is the foundation of mechanical longevity. By selecting the right material and observing professional installation standards, you protect the equipment and the structural integrity of the roof itself.