The right shim stock thickness can correct a small gap before it leads to misalignment, vibration, or wear problems. Engineers, machinists, maintenance teams, and quality professionals also have to account for the material, temper, tolerance, load, temperature, and cutting method.
Why Shim Stock Thickness Matters
Shim stock can fill a space, change the component height, or align mating parts. Too little material can leave the assembly outside tolerance, and too much can alter the load path or create interference. Very thin stock supports fine adjustments, but it also deforms more easily. Thicker stock typically handles compressive loads more effectively.
Metals and plastics differ in their strength, hardness, corrosion resistance, and thermal expansion. Since heat cycles can alter a gap, select the material and thickness for the full service range.
Common Thickness Ranges and Tolerances
The most common metal gauges are 0.0005, 0.001, 0.002, 0.003, 0.005, 0.010, 0.015, 0.020, 0.025, and 0.031 inch. The range is about 0.013 to 0.787 mm, although specialty products may extend beyond it.
Tolerance is dependent on the material and nominal thickness. Stainless steel tolerance is listed from +/-0.000025 inch at 0.0005 inch thick to +/-0.001 inch at 0.031 inch. Plastic stock from 0.0005 through 0.020 inch is listed at +/-5%; sizes above 0.025 inch are listed at +/-10%. Confirm the most current product specifications.
If one gauge cannot create the needed correction, add thicknesses to achieve the target. Limit stacks to three or four pieces, as more interfaces can increase compliance and reduce preload. Plus, a single shim is usually more rigid.
Measurement Techniques for Shim Stock
For loose stock, use a clean, calibrated outside micrometer with the right resolution. Close it with the ratchet or friction thimble for consistent measuring force, also avoiding burrs or damaged edges.
Calipers work for quick checks on thicker stock, but they might lack the resolution for thin material. To check a gap, try progressively thicker feeler-gauge blades until one fits.
However, critical aerospace, medical, or inspection-controlled work may need accredited-lab verification, especially when shop instruments cannot provide the required uncertainty.
Measuring Shim Stock Thickness: Best Practices
Clean the contact faces, zero the instrument, confirm calibration, and measure several different points. Multiple readings can help reveal variation, edge damage, or a local crease.
To streamline later repairs or repeat orders, record the material, nominal gauge, readings, instrument ID, calibration status, operator, date, and lot.
Stainless Steel Shim Thickness
Stainless steel shim stock is available in 300-series grades like 301, 302/304, and 316, combining strength with heat and corrosion resistance. Full-hard material offers greater stiffness, while annealed stock is simpler to form. Consider 316 for chloride exposure and choose a gauge that balances fine adjustment with load support.
Brass Shim Stock: Thickness and Uses
Most brass shim stock gauges run from 0.001 through 0.031 inch, depending on the format. Alloy 260 half-hard brass is formable, corrosion resistant, electrically conductive, and low in magnetic permeability. However, stainless generally suits higher loads or harsher temperatures; brass might be better when conductivity is the main concern.
Steel Shim Stock Thickness
Low-carbon steel is economical, making it a strong choice for dry, controlled environments. Blue-tempered high-carbon steel adds hardness, wear resistance, and spring characteristics. Thin hardened stock allows precise adjustment, but it can also be less forgiving to cut. Review corrosion exposure before selecting uncoated steel.
Selecting Shim Stock Thickness by Application
The measured gap and allowable alignment tolerance can be used as the starting point. Then, review the application:
- Aerospace: Check drawing tolerances, load, fatigue, temperature, weight, material specification, and lot traceability.
- Automotive: Review vibration, thermal cycling, corrosion exposure, assembly rate, and service access.
- Medical devices: Confirm material compatibility, cleanliness, documentation, and the design controls.
- General manufacturing: Compare load, environment, adjustment range, cutting method, maintenance needs, and cost.
Fabrication and Cutting Considerations
Thin stock can typically be cut with scissors or shears. More complex profiles need stamping, laser cutting, waterjet cutting, wire EDM, or CNC machining. Laser cutting is fast, but heat input and burrs demand careful attention. Waterjet cutting avoids heat-affected zones; stamping suits repeat production; slitting creates narrow coils or strips.
Profile tolerance ultimately comes down to the material, thickness, geometry, equipment, and finishing.
Ordering, Certifications, and Traceability
Confirm the alloy specification, such as ASTM A666/A666M for austenitic stainless or ASTM B36/B36M for brass. As required, request a certificate of conformance, mill test report, test data, country of origin, and lot ID.
Make sure to store sheets flat, clean, and dry, with protective interleaving. Clearly label packages by material, temper, thickness, lot, and receipt date, and separate partial sheets so similar gauges are not accidentally mixed.
Shim Stock Services from Trinity Brand Industries
Trinity Brand Industries supplies shim stock flat sheets in stainless steel, brass, carbon steel, blue-tempered steel, and other materials. Our fabrication services create custom shims when standard dimensions are inadequate, and we also provide material certification.
Frequently Asked Questions
How do you measure shim stock thickness?
Use a clean and calibrated micrometer, apply consistent measuring force, and record readings at multiple points. A caliper can work for thicker stock; a feeler gauge is better for checking the gap that the shim must fill.
How thin can a shim be?
Shim stock can be as thin as 0.0005 inch, or about 0.013 mm, depending on the material and supplier. Extremely thin stock calls for careful handling, as it can crease or deform easily.
What are the standard shim sizes?
Common metal thicknesses range from 0.0005 to 0.031 inch, while sheet widths, lengths, rolls, and pre-cut shapes vary by material and manufacturer. Start with the required correction, then confirm the available dimensions and tolerances.
Get the Right Shim for the Job
Accurate gap measurements, realistic load and temperature requirements, and correct material specification make thickness selection much easier. Browse Trinity Brand’s full selection or contact the team to request a quote for custom-cut shims.
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