A compression spring’s outside diameter needs enough clearance for its guide rod or housing, but the nominal coil size alone does not establish the allowed variation. Lee Spring publishes metric outside-diameter tolerance bands for its covered stock compression springs. This chart keeps those bands tied to the manufacturer and series limits, and preserves the gaps between listed diameter ranges rather than filling them with assumed values.

Spring Coil Diameter Tolerance Chart

Match the nominal spring outside diameter to a published band. Use the separate upper and lower values where the source specifies an asymmetric tolerance.

For a symmetric band, the listed upper and lower tolerance magnitudes are equal. A nominal 10 mm OD falls in the 7.62–12.70 mm band, which carries ±0.20 mm. The corresponding tolerance zone is 9.80 to 10.20 mm. In the 3.05–6.10 mm band, the source specifies +0.08/−0.13 mm, so a 5 mm nominal OD spans 4.87 to 5.08 mm. Do not convert an asymmetric band into a symmetric plus-minus value.

The table is specific to stock compression springs covered by Lee Spring’s general tolerance page. The source lists exclusions for its Lite Pressure, HEFTY Die, REDUX and MIL-SPEC products and notes exceptions for springs made to DIN requirements. A catalog spring may have product-specific details, while a custom spring may use a drawing tolerance. Check the exact part number or controlled drawing before inspection.

Nominal OD is not the same as mean coil diameter or inside diameter. For a close-fitting assembly, the spring’s OD must be considered against the available hole, and the spring’s free shape can vary with its ends and manufacturing condition. This table only gives an outside-diameter tolerance band; it does not specify wire diameter, free length, spring rate, solid height, load or perpendicularity.

To evaluate a measurement, first identify the measurement method and whether the spring is relaxed and uncompressed. Use an instrument with adequate resolution and suitable contact force; thin wire can move or distort under an aggressive measurement. Measure at more than one angular position if coil ovality matters to the application. A single caliper reading may not capture the maximum diameter of a non-round spring.

The source includes gaps between some published metric ranges. For example, not every nominal value between one listed band and the next is covered. If a spring falls into a gap, do not choose the nearest band automatically or interpolate a tolerance. Request the manufacturer’s specification or use the tolerance defined on the part drawing. The same rule applies to a special series or a product whose specification differs from the generic stock table.

A common mistake is treating a stock tolerance as a universal spring standard. These are Lee Spring’s published values for its covered products, not a general requirement for every spring supplier. Another is using the OD limit to approve a spring that binds in its housing. The actual assembly needs allowance for dimensional variation, motion, temperature, load and neighboring geometry.

When checking incoming parts, record the nominal diameter, source series, measurement method and maximum observed OD. Compare against the correct asymmetric or symmetric band, then resolve borderline cases using the drawing and the applicable inspection plan. If the functional clearance is critical, verify the mating housing and the spring under the real assembly conditions rather than relying on a nominal value alone.

For an assembly with a guide rod, compare the spring’s inside clearance as well as its outside diameter; this table covers OD only and cannot predict rubbing or buckling. If the spring sits in a bore, account for finish, misalignment and the spring’s movement during compression.

Sources

Lee Spring’s Engineering Notes and Tolerances page provides the stock compression outside-diameter bands and identifies the product exclusions and DIN exceptions.