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ISO clearance fits H7 g6

The ISO sliding fit H7/g6 guarantees a minimum clearance ranging from 0.005 mm / 0.00020 in for a 10 mm diameter to 0.018 mm / 0.00071 in for 400 mm, always maintaining a positive space that allows free rotation or sliding of parts. This is a clearance fit within the basic hole system, where the hole is machined with H7 tolerance (lower deviation zero) and the shaft with g6 tolerance (negative fundamental deviation). This combination generates small but safe clearances, suitable for applications requiring high guidance precision, such as spindles, idler gears, camshafts, or lubricated plain bearings.

Table of H7/g6 tolerance values

Section titled “Table of H7/g6 tolerance values”
Nominal diameter (mm / in) Hole tolerance H7 (mm / in) Shaft tolerance g6 (mm / in) Minimum clearance (mm / in) Maximum clearance (mm / in)
10 / 0.394 0 to +0.015 / 0 to +0.00059 -0.014 to -0.005 / -0.00055 to -0.00020 0.005 / 0.00020 0.029 / 0.00114
30 / 1.181 0 to +0.021 / 0 to +0.00083 -0.020 to -0.007 / -0.00079 to -0.00028 0.007 / 0.00028 0.041 / 0.00161
50 / 1.969 0 to +0.025 / 0 to +0.00098 -0.025 to -0.009 / -0.00098 to -0.00035 0.009 / 0.00035 0.050 / 0.00197
75 / 2.953 0 to +0.030 / 0 to +0.00118 -0.029 to -0.010 / -0.00114 to -0.00039 0.010 / 0.00039 0.059 / 0.00232
100 / 3.937 0 to +0.035 / 0 to +0.00138 -0.034 to -0.012 / -0.00134 to -0.00047 0.012 / 0.00047 0.069 / 0.00272
150 / 5.906 0 to +0.040 / 0 to +0.00157 -0.039 to -0.014 / -0.00154 to -0.00055 0.014 / 0.00055 0.079 / 0.00311
250 / 9.842 0 to +0.046 / 0 to +0.00181 -0.044 to -0.015 / -0.00173 to -0.00059 0.015 / 0.00059 0.090 / 0.00354
400 / 15.748 0 to +0.057 / 0 to +0.00224 -0.054 to -0.018 / -0.00213 to -0.00071 0.018 / 0.00071 0.111 / 0.00437

Tolerances according to ISO 286‑2:2010. Inch measurements rounded to five decimal places.

Real application examples

Section titled “Real application examples”
  • Spindle and spline shaft guides – where axial movement must be smooth but without play.
  • Idler gears and sliding sprockets – allow axial displacement with precise centering.
  • Crankshaft and camshaft bearings – in combustion engines, secured by forced lubrication.
  • Precision valves and stems – in pneumatic and hydraulic systems requiring dynamic sealing.
  • Machine tool columns – slides of carriages and tables in milling machines or lathes.
  • Measuring instruments – micrometers and comparators with micrometer displacements without lateral play.

Symbol interpretation

Section titled “Symbol interpretation”

The designation H7/g6 breaks down into four numerical components: the hole has fundamental tolerance H (lower deviation 0 mm), grade IT7 (for 50 mm this equals 0.025 mm bandwidth); the shaft has fundamental tolerance g (negative upper deviation, typically ‑0.009 mm for 50 mm) and grade IT6 (0.016 mm for 50 mm). The number after the letter indicates the ISO tolerance grade; a lower number corresponds to more precise manufacturing. The lowercase notation (g6) always refers to the shaft, while the uppercase (H7) identifies the hole. The system is basic hole, meaning the hole size remains constant with a lower limit of zero and the shaft is varied to obtain the desired clearance.

Comparison with ANSI

Section titled “Comparison with ANSI”

The H7/g6 fit finds its functional equivalent in the ANSI B4.1 standard as class RC1 (Close Sliding Fit), which for a nominal diameter of 50 mm offers a typical minimum clearance around 0.008 mm / 0.0003 in and a maximum of approximately 0.025 mm / 0.0010 in. Unlike the ISO basic hole system (the hole is maintained in H), ANSI allows both basic hole and basic shaft, and tolerances are expressed in thousandths of an inch. For example, an RC1 fit for a 2‑inch shaft is typically specified with hole limits +0.3 mils / ‑0 mils and shaft limits ‑0.7 mils / ‑1.1 mils, resulting in comparable but not identical clearances to H7/g6. The selection between the two systems depends on the market and reference drawings.

Frequently Asked Questions (FAQ)

Section titled “Frequently Asked Questions (FAQ)”

What is the minimum clearance of H7/g6 for a 50 mm diameter?

Section titled “What is the minimum clearance of H7/g6 for a 50 mm diameter?”

The minimum clearance is 0.009 mm / 0.00035 in, and the maximum reaches 0.050 mm / 0.00197 in at 20 °C.

Can I machine an H7/g6 fit directly in inches?

Section titled “Can I machine an H7/g6 fit directly in inches?”

Yes, the tolerance values are converted to inches while maintaining the same limits: for 50 mm, the hole remains from 1.9685 to 1.9695 in and the shaft from 1.9665 to 1.9670 in approximately.

What manufacturing process achieves the required IT6/IT7 quality?

Section titled “What manufacturing process achieves the required IT6/IT7 quality?”

IT6 quality is obtained by cylindrical grinding, precision turning, or broaching; IT7 is achieved with careful turning, milling, or boring. Lapping or honing lead to higher grades.

What is the difference between H7/g6 and H7/h6?

Section titled “What is the difference between H7/g6 and H7/h6?”

H7/h6 is a location fit with virtually zero clearance (minimum 0 µm for any diameter), while H7/g6 always ensures a positive minimum clearance, allowing movement even without lubrication.

Can H7/g6 be applied to non‑cylindrical parts?

Section titled “Can H7/g6 be applied to non‑cylindrical parts?”

Yes, although originally intended for shafts and holes, the concept extends to flat fits (prismatic guides) where controlled clearance guarantees sliding without play.

What is the suitable operating temperature range for this fit?

Section titled “What is the suitable operating temperature range for this fit?”

H7/g6 is intended for ambient temperature (20 °C / 68 °F). With variations above 30 °C / 86 °F, thermal expansion must be compensated, especially if the shaft and hole materials are different.

References consulted

Section titled “References consulted”

References

Section titled “References”