ISO Preferred Fits Chart
The ten ISO 286 preferred hole-basis fits, from loose running to force, with what each one is for and the limits it gives at standard sizes from 1 to 250 mm and at common inch sizes. Every number is computed from the ISO 286 formulas and checked against the published tables. For any other size or class, use the fit tolerance calculator.
The preferred fits at a glance
| Hole basis | Shaft basis | Fit | Type | Typical use | Assembly |
|---|---|---|---|---|---|
| H11/c11 | C11/h11 | Loose running | Clearance | Generous clearance for pins and shafts that have to keep moving through dirt, paint, heat growth or rough commercial stock: hinge and linkage pins on farm and construction equipment. | Drops together by hand with visible play. |
| H9/d9 | D9/h9 | Free running | Clearance | Running clearance where precision matters less than keeping the shaft free: big temperature swings, high surface speeds or heavily loaded plain journals. | Slides together by hand. |
| H8/f7 | F8/h7 | Close running | Clearance | Accurate running fit for spindles, gearbox shafts and plain bearings in machine tools at moderate speed and load. Also locates parts that still have to turn. | Slides together by hand with a film of oil. |
| H7/g6 | G7/h6 | Sliding | Clearance | Parts that do not run continuously but must slide or turn freely and still locate well: sliding gears and collars, guide pins, locating spigots, piston pins. | Pushes together by hand. |
| H7/h6 | H7/h6 | Locational clearance | Clearance | Snug location of parts that do not move in service but have to come apart for maintenance: spigots, pilots, fixture locators, parts clamped by bolts. | Pushes together by hand; the tightest pair is line to line. |
| H7/k6 | K7/h6 | Locational transition | Transition | Accurate location where a little interference is acceptable and a little clearance is tolerable: gears, pulleys and couplings on keyed shafts, bearing inner rings under light load. | Goes together with a soft mallet or light press. |
| H7/n6 | N7/h6 | Locational transition (tight) | Transition | More accurate location than k6 where more interference is fine: bushings, gears and hubs that must not rock, parts that see vibration. | Needs a press; comes apart with a puller. |
| H7/p6 | P7/h6 | Locational interference | Interference | Rigid, aligned location without high bore stress: pressed bushings, sleeves and light hubs that must not creep. Not meant to carry torque by friction alone. | Pressed in cold. |
| H7/s6 | S7/h6 | Medium drive | Interference | Permanent assemblies of ordinary steel parts, or shrink fits on thin sections. About the tightest fit cast iron hubs take without cracking. | Heavy press, or heat the hub. |
| H7/u6 | U7/h6 | Force | Interference | Highly stressed permanent joints that carry torque through the fit, where pressing would take too much force: shrink-fit gears, rings and couplings on steel shafts. | Shrink fit: heat the hub or freeze the shaft. |
Clearance and interference by size (µm)
Maximum / minimum clearance in micrometers (1 µm = 0.001 mm, about 0.00004 in). Negative numbers are interference. Sizes are the top of each ISO size step, so a value holds for every size down to the previous one.
| Size | H11/c11 | H9/d9 | H8/f7 | H7/g6 | H7/h6 | H7/k6 | H7/n6 | H7/p6 | H7/s6 | H7/u6 |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 mm | +180 / +60 | +70 / +20 | +30 / +6 | +18 / +2 | +16 / 0 | +10 / -6 | +6 / -10 | +4 / -12 | -4 / -20 | -8 / -24 |
| 3 mm | +180 / +60 | +70 / +20 | +30 / +6 | +18 / +2 | +16 / 0 | +10 / -6 | +6 / -10 | +4 / -12 | -4 / -20 | -8 / -24 |
| 6 mm | +220 / +70 | +90 / +30 | +40 / +10 | +24 / +4 | +20 / 0 | +11 / -9 | +4 / -16 | 0 / -20 | -7 / -27 | -11 / -31 |
| 10 mm | +260 / +80 | +112 / +40 | +50 / +13 | +29 / +5 | +24 / 0 | +14 / -10 | +5 / -19 | 0 / -24 | -8 / -32 | -13 / -37 |
| 18 mm | +315 / +95 | +136 / +50 | +61 / +16 | +35 / +6 | +29 / 0 | +17 / -12 | +6 / -23 | 0 / -29 | -10 / -39 | -15 / -44 |
| 30 mm | +370 / +110 | +169 / +65 | +74 / +20 | +41 / +7 | +34 / 0 | +19 / -15 | +6 / -28 | -1 / -35 | -14 / -48 | -27 / -61 |
| 50 mm | +450 / +130 | +204 / +80 | +89 / +25 | +50 / +9 | +41 / 0 | +23 / -18 | +8 / -33 | -1 / -42 | -18 / -59 | -45 / -86 |
| 80 mm | +530 / +150 | +248 / +100 | +106 / +30 | +59 / +10 | +49 / 0 | +28 / -21 | +10 / -39 | -2 / -51 | -29 / -78 | -72 / -121 |
| 120 mm | +620 / +180 | +294 / +120 | +125 / +36 | +69 / +12 | +57 / 0 | +32 / -25 | +12 / -45 | -2 / -59 | -44 / -101 | -109 / -166 |
| 180 mm | +730 / +230 | +345 / +145 | +146 / +43 | +79 / +14 | +65 / 0 | +37 / -28 | +13 / -52 | -3 / -68 | -68 / -133 | -170 / -235 |
| 250 mm | +860 / +280 | +400 / +170 | +168 / +50 | +90 / +15 | +75 / 0 | +42 / -33 | +15 / -60 | -4 / -79 | -94 / -169 | -238 / -313 |
The same fits at inch sizes (in)
Maximum / minimum clearance in inches for the ISO fits applied to inch nominal sizes (converted to millimeters, then to the ISO size step). These are not ANSI B4.1 values; see the note on inch classes below.
| Size | H11/c11 | H9/d9 | H8/f7 | H7/g6 | H7/h6 | H7/k6 | H7/n6 | H7/p6 | H7/s6 | H7/u6 |
|---|---|---|---|---|---|---|---|---|---|---|
| 1/4 in | +0.01024 / +0.00315 | +0.00441 / +0.00157 | +0.00197 / +0.00051 | +0.00114 / +0.00020 | +0.00094 / 0 | +0.00055 / -0.00039 | +0.00020 / -0.00075 | 0 / -0.00094 | -0.00031 / -0.00126 | -0.00051 / -0.00146 |
| 1/2 in | +0.01240 / +0.00374 | +0.00535 / +0.00197 | +0.00240 / +0.00063 | +0.00138 / +0.00024 | +0.00114 / 0 | +0.00067 / -0.00047 | +0.00024 / -0.00091 | 0 / -0.00114 | -0.00039 / -0.00154 | -0.00059 / -0.00173 |
| 3/4 in | +0.01457 / +0.00433 | +0.00665 / +0.00256 | +0.00291 / +0.00079 | +0.00161 / +0.00028 | +0.00134 / 0 | +0.00075 / -0.00059 | +0.00024 / -0.00110 | -0.00004 / -0.00138 | -0.00055 / -0.00189 | -0.00079 / -0.00213 |
| 1 in | +0.01457 / +0.00433 | +0.00665 / +0.00256 | +0.00291 / +0.00079 | +0.00161 / +0.00028 | +0.00134 / 0 | +0.00075 / -0.00059 | +0.00024 / -0.00110 | -0.00004 / -0.00138 | -0.00055 / -0.00189 | -0.00106 / -0.00240 |
| 1-1/2 in | +0.01732 / +0.00472 | +0.00803 / +0.00315 | +0.00350 / +0.00098 | +0.00197 / +0.00035 | +0.00161 / 0 | +0.00091 / -0.00071 | +0.00031 / -0.00130 | -0.00004 / -0.00165 | -0.00071 / -0.00232 | -0.00138 / -0.00299 |
| 2 in | +0.02047 / +0.00551 | +0.00976 / +0.00394 | +0.00417 / +0.00118 | +0.00232 / +0.00039 | +0.00193 / 0 | +0.00110 / -0.00083 | +0.00039 / -0.00154 | -0.00008 / -0.00201 | -0.00091 / -0.00283 | -0.00224 / -0.00417 |
Have bores and shafts to make to these limits? , or check a one-off size in the fit calculator.
Hole and shaft limits for each fit
Maximum / minimum limits. Metric rows in millimeters, inch rows in inches (converted from the metric limits, five places so nothing is lost to rounding). The fit column is maximum / minimum clearance; negative is interference.
H11/c11: loose running
| Size | Hole H11 | Shaft c11 | Fit |
|---|---|---|---|
| 1 mm | 1.060 / 1.000 | 0.940 / 0.880 | +0.180 / +0.060 |
| 3 mm | 3.060 / 3.000 | 2.940 / 2.880 | +0.180 / +0.060 |
| 6 mm | 6.075 / 6.000 | 5.930 / 5.855 | +0.220 / +0.070 |
| 10 mm | 10.090 / 10.000 | 9.920 / 9.830 | +0.260 / +0.080 |
| 18 mm | 18.110 / 18.000 | 17.905 / 17.795 | +0.315 / +0.095 |
| 30 mm | 30.130 / 30.000 | 29.890 / 29.760 | +0.370 / +0.110 |
| 50 mm | 50.160 / 50.000 | 49.870 / 49.710 | +0.450 / +0.130 |
| 80 mm | 80.190 / 80.000 | 79.850 / 79.660 | +0.530 / +0.150 |
| 120 mm | 120.220 / 120.000 | 119.820 / 119.600 | +0.620 / +0.180 |
| 180 mm | 180.250 / 180.000 | 179.770 / 179.520 | +0.730 / +0.230 |
| 250 mm | 250.290 / 250.000 | 249.720 / 249.430 | +0.860 / +0.280 |
| 1/4 in | 0.25354 / 0.25000 | 0.24685 / 0.24331 | +0.01024 / +0.00315 |
| 1/2 in | 0.50433 / 0.50000 | 0.49626 / 0.49193 | +0.01240 / +0.00374 |
| 3/4 in | 0.75512 / 0.75000 | 0.74567 / 0.74055 | +0.01457 / +0.00433 |
| 1 in | 1.00512 / 1.00000 | 0.99567 / 0.99055 | +0.01457 / +0.00433 |
| 1-1/2 in | 1.50630 / 1.50000 | 1.49528 / 1.48898 | +0.01732 / +0.00472 |
| 2 in | 2.00748 / 2.00000 | 1.99449 / 1.98701 | +0.02047 / +0.00551 |
H9/d9: free running
| Size | Hole H9 | Shaft d9 | Fit |
|---|---|---|---|
| 1 mm | 1.025 / 1.000 | 0.980 / 0.955 | +0.070 / +0.020 |
| 3 mm | 3.025 / 3.000 | 2.980 / 2.955 | +0.070 / +0.020 |
| 6 mm | 6.030 / 6.000 | 5.970 / 5.940 | +0.090 / +0.030 |
| 10 mm | 10.036 / 10.000 | 9.960 / 9.924 | +0.112 / +0.040 |
| 18 mm | 18.043 / 18.000 | 17.950 / 17.907 | +0.136 / +0.050 |
| 30 mm | 30.052 / 30.000 | 29.935 / 29.883 | +0.169 / +0.065 |
| 50 mm | 50.062 / 50.000 | 49.920 / 49.858 | +0.204 / +0.080 |
| 80 mm | 80.074 / 80.000 | 79.900 / 79.826 | +0.248 / +0.100 |
| 120 mm | 120.087 / 120.000 | 119.880 / 119.793 | +0.294 / +0.120 |
| 180 mm | 180.100 / 180.000 | 179.855 / 179.755 | +0.345 / +0.145 |
| 250 mm | 250.115 / 250.000 | 249.830 / 249.715 | +0.400 / +0.170 |
| 1/4 in | 0.25142 / 0.25000 | 0.24843 / 0.24701 | +0.00441 / +0.00157 |
| 1/2 in | 0.50169 / 0.50000 | 0.49803 / 0.49634 | +0.00535 / +0.00197 |
| 3/4 in | 0.75205 / 0.75000 | 0.74744 / 0.74539 | +0.00665 / +0.00256 |
| 1 in | 1.00205 / 1.00000 | 0.99744 / 0.99539 | +0.00665 / +0.00256 |
| 1-1/2 in | 1.50244 / 1.50000 | 1.49685 / 1.49441 | +0.00803 / +0.00315 |
| 2 in | 2.00291 / 2.00000 | 1.99606 / 1.99315 | +0.00976 / +0.00394 |
H8/f7: close running
| Size | Hole H8 | Shaft f7 | Fit |
|---|---|---|---|
| 1 mm | 1.014 / 1.000 | 0.994 / 0.984 | +0.030 / +0.006 |
| 3 mm | 3.014 / 3.000 | 2.994 / 2.984 | +0.030 / +0.006 |
| 6 mm | 6.018 / 6.000 | 5.990 / 5.978 | +0.040 / +0.010 |
| 10 mm | 10.022 / 10.000 | 9.987 / 9.972 | +0.050 / +0.013 |
| 18 mm | 18.027 / 18.000 | 17.984 / 17.966 | +0.061 / +0.016 |
| 30 mm | 30.033 / 30.000 | 29.980 / 29.959 | +0.074 / +0.020 |
| 50 mm | 50.039 / 50.000 | 49.975 / 49.950 | +0.089 / +0.025 |
| 80 mm | 80.046 / 80.000 | 79.970 / 79.940 | +0.106 / +0.030 |
| 120 mm | 120.054 / 120.000 | 119.964 / 119.929 | +0.125 / +0.036 |
| 180 mm | 180.063 / 180.000 | 179.957 / 179.917 | +0.146 / +0.043 |
| 250 mm | 250.072 / 250.000 | 249.950 / 249.904 | +0.168 / +0.050 |
| 1/4 in | 0.25087 / 0.25000 | 0.24949 / 0.24890 | +0.00197 / +0.00051 |
| 1/2 in | 0.50106 / 0.50000 | 0.49937 / 0.49866 | +0.00240 / +0.00063 |
| 3/4 in | 0.75130 / 0.75000 | 0.74921 / 0.74839 | +0.00291 / +0.00079 |
| 1 in | 1.00130 / 1.00000 | 0.99921 / 0.99839 | +0.00291 / +0.00079 |
| 1-1/2 in | 1.50154 / 1.50000 | 1.49902 / 1.49803 | +0.00350 / +0.00098 |
| 2 in | 2.00181 / 2.00000 | 1.99882 / 1.99764 | +0.00417 / +0.00118 |
H7/g6: sliding
| Size | Hole H7 | Shaft g6 | Fit |
|---|---|---|---|
| 1 mm | 1.010 / 1.000 | 0.998 / 0.992 | +0.018 / +0.002 |
| 3 mm | 3.010 / 3.000 | 2.998 / 2.992 | +0.018 / +0.002 |
| 6 mm | 6.012 / 6.000 | 5.996 / 5.988 | +0.024 / +0.004 |
| 10 mm | 10.015 / 10.000 | 9.995 / 9.986 | +0.029 / +0.005 |
| 18 mm | 18.018 / 18.000 | 17.994 / 17.983 | +0.035 / +0.006 |
| 30 mm | 30.021 / 30.000 | 29.993 / 29.980 | +0.041 / +0.007 |
| 50 mm | 50.025 / 50.000 | 49.991 / 49.975 | +0.050 / +0.009 |
| 80 mm | 80.030 / 80.000 | 79.990 / 79.971 | +0.059 / +0.010 |
| 120 mm | 120.035 / 120.000 | 119.988 / 119.966 | +0.069 / +0.012 |
| 180 mm | 180.040 / 180.000 | 179.986 / 179.961 | +0.079 / +0.014 |
| 250 mm | 250.046 / 250.000 | 249.985 / 249.956 | +0.090 / +0.015 |
| 1/4 in | 0.25059 / 0.25000 | 0.24980 / 0.24945 | +0.00114 / +0.00020 |
| 1/2 in | 0.50071 / 0.50000 | 0.49976 / 0.49933 | +0.00138 / +0.00024 |
| 3/4 in | 0.75083 / 0.75000 | 0.74972 / 0.74921 | +0.00161 / +0.00028 |
| 1 in | 1.00083 / 1.00000 | 0.99972 / 0.99921 | +0.00161 / +0.00028 |
| 1-1/2 in | 1.50098 / 1.50000 | 1.49965 / 1.49902 | +0.00197 / +0.00035 |
| 2 in | 2.00118 / 2.00000 | 1.99961 / 1.99886 | +0.00232 / +0.00039 |
H7/h6: locational clearance
| Size | Hole H7 | Shaft h6 | Fit |
|---|---|---|---|
| 1 mm | 1.010 / 1.000 | 1.000 / 0.994 | +0.016 / 0 |
| 3 mm | 3.010 / 3.000 | 3.000 / 2.994 | +0.016 / 0 |
| 6 mm | 6.012 / 6.000 | 6.000 / 5.992 | +0.020 / 0 |
| 10 mm | 10.015 / 10.000 | 10.000 / 9.991 | +0.024 / 0 |
| 18 mm | 18.018 / 18.000 | 18.000 / 17.989 | +0.029 / 0 |
| 30 mm | 30.021 / 30.000 | 30.000 / 29.987 | +0.034 / 0 |
| 50 mm | 50.025 / 50.000 | 50.000 / 49.984 | +0.041 / 0 |
| 80 mm | 80.030 / 80.000 | 80.000 / 79.981 | +0.049 / 0 |
| 120 mm | 120.035 / 120.000 | 120.000 / 119.978 | +0.057 / 0 |
| 180 mm | 180.040 / 180.000 | 180.000 / 179.975 | +0.065 / 0 |
| 250 mm | 250.046 / 250.000 | 250.000 / 249.971 | +0.075 / 0 |
| 1/4 in | 0.25059 / 0.25000 | 0.25000 / 0.24965 | +0.00094 / 0 |
| 1/2 in | 0.50071 / 0.50000 | 0.50000 / 0.49957 | +0.00114 / 0 |
| 3/4 in | 0.75083 / 0.75000 | 0.75000 / 0.74949 | +0.00134 / 0 |
| 1 in | 1.00083 / 1.00000 | 1.00000 / 0.99949 | +0.00134 / 0 |
| 1-1/2 in | 1.50098 / 1.50000 | 1.50000 / 1.49937 | +0.00161 / 0 |
| 2 in | 2.00118 / 2.00000 | 2.00000 / 1.99925 | +0.00193 / 0 |
H7/k6: locational transition
| Size | Hole H7 | Shaft k6 | Fit |
|---|---|---|---|
| 1 mm | 1.010 / 1.000 | 1.006 / 1.000 | +0.010 / -0.006 |
| 3 mm | 3.010 / 3.000 | 3.006 / 3.000 | +0.010 / -0.006 |
| 6 mm | 6.012 / 6.000 | 6.009 / 6.001 | +0.011 / -0.009 |
| 10 mm | 10.015 / 10.000 | 10.010 / 10.001 | +0.014 / -0.010 |
| 18 mm | 18.018 / 18.000 | 18.012 / 18.001 | +0.017 / -0.012 |
| 30 mm | 30.021 / 30.000 | 30.015 / 30.002 | +0.019 / -0.015 |
| 50 mm | 50.025 / 50.000 | 50.018 / 50.002 | +0.023 / -0.018 |
| 80 mm | 80.030 / 80.000 | 80.021 / 80.002 | +0.028 / -0.021 |
| 120 mm | 120.035 / 120.000 | 120.025 / 120.003 | +0.032 / -0.025 |
| 180 mm | 180.040 / 180.000 | 180.028 / 180.003 | +0.037 / -0.028 |
| 250 mm | 250.046 / 250.000 | 250.033 / 250.004 | +0.042 / -0.033 |
| 1/4 in | 0.25059 / 0.25000 | 0.25039 / 0.25004 | +0.00055 / -0.00039 |
| 1/2 in | 0.50071 / 0.50000 | 0.50047 / 0.50004 | +0.00067 / -0.00047 |
| 3/4 in | 0.75083 / 0.75000 | 0.75059 / 0.75008 | +0.00075 / -0.00059 |
| 1 in | 1.00083 / 1.00000 | 1.00059 / 1.00008 | +0.00075 / -0.00059 |
| 1-1/2 in | 1.50098 / 1.50000 | 1.50071 / 1.50008 | +0.00091 / -0.00071 |
| 2 in | 2.00118 / 2.00000 | 2.00083 / 2.00008 | +0.00110 / -0.00083 |
H7/n6: locational transition (tight)
| Size | Hole H7 | Shaft n6 | Fit |
|---|---|---|---|
| 1 mm | 1.010 / 1.000 | 1.010 / 1.004 | +0.006 / -0.010 |
| 3 mm | 3.010 / 3.000 | 3.010 / 3.004 | +0.006 / -0.010 |
| 6 mm | 6.012 / 6.000 | 6.016 / 6.008 | +0.004 / -0.016 |
| 10 mm | 10.015 / 10.000 | 10.019 / 10.010 | +0.005 / -0.019 |
| 18 mm | 18.018 / 18.000 | 18.023 / 18.012 | +0.006 / -0.023 |
| 30 mm | 30.021 / 30.000 | 30.028 / 30.015 | +0.006 / -0.028 |
| 50 mm | 50.025 / 50.000 | 50.033 / 50.017 | +0.008 / -0.033 |
| 80 mm | 80.030 / 80.000 | 80.039 / 80.020 | +0.010 / -0.039 |
| 120 mm | 120.035 / 120.000 | 120.045 / 120.023 | +0.012 / -0.045 |
| 180 mm | 180.040 / 180.000 | 180.052 / 180.027 | +0.013 / -0.052 |
| 250 mm | 250.046 / 250.000 | 250.060 / 250.031 | +0.015 / -0.060 |
| 1/4 in | 0.25059 / 0.25000 | 0.25075 / 0.25039 | +0.00020 / -0.00075 |
| 1/2 in | 0.50071 / 0.50000 | 0.50091 / 0.50047 | +0.00024 / -0.00091 |
| 3/4 in | 0.75083 / 0.75000 | 0.75110 / 0.75059 | +0.00024 / -0.00110 |
| 1 in | 1.00083 / 1.00000 | 1.00110 / 1.00059 | +0.00024 / -0.00110 |
| 1-1/2 in | 1.50098 / 1.50000 | 1.50130 / 1.50067 | +0.00031 / -0.00130 |
| 2 in | 2.00118 / 2.00000 | 2.00154 / 2.00079 | +0.00039 / -0.00154 |
H7/p6: locational interference
| Size | Hole H7 | Shaft p6 | Fit |
|---|---|---|---|
| 1 mm | 1.010 / 1.000 | 1.012 / 1.006 | +0.004 / -0.012 |
| 3 mm | 3.010 / 3.000 | 3.012 / 3.006 | +0.004 / -0.012 |
| 6 mm | 6.012 / 6.000 | 6.020 / 6.012 | 0 / -0.020 |
| 10 mm | 10.015 / 10.000 | 10.024 / 10.015 | 0 / -0.024 |
| 18 mm | 18.018 / 18.000 | 18.029 / 18.018 | 0 / -0.029 |
| 30 mm | 30.021 / 30.000 | 30.035 / 30.022 | -0.001 / -0.035 |
| 50 mm | 50.025 / 50.000 | 50.042 / 50.026 | -0.001 / -0.042 |
| 80 mm | 80.030 / 80.000 | 80.051 / 80.032 | -0.002 / -0.051 |
| 120 mm | 120.035 / 120.000 | 120.059 / 120.037 | -0.002 / -0.059 |
| 180 mm | 180.040 / 180.000 | 180.068 / 180.043 | -0.003 / -0.068 |
| 250 mm | 250.046 / 250.000 | 250.079 / 250.050 | -0.004 / -0.079 |
| 1/4 in | 0.25059 / 0.25000 | 0.25094 / 0.25059 | 0 / -0.00094 |
| 1/2 in | 0.50071 / 0.50000 | 0.50114 / 0.50071 | 0 / -0.00114 |
| 3/4 in | 0.75083 / 0.75000 | 0.75138 / 0.75087 | -0.00004 / -0.00138 |
| 1 in | 1.00083 / 1.00000 | 1.00138 / 1.00087 | -0.00004 / -0.00138 |
| 1-1/2 in | 1.50098 / 1.50000 | 1.50165 / 1.50102 | -0.00004 / -0.00165 |
| 2 in | 2.00118 / 2.00000 | 2.00201 / 2.00126 | -0.00008 / -0.00201 |
H7/s6: medium drive
| Size | Hole H7 | Shaft s6 | Fit |
|---|---|---|---|
| 1 mm | 1.010 / 1.000 | 1.020 / 1.014 | -0.004 / -0.020 |
| 3 mm | 3.010 / 3.000 | 3.020 / 3.014 | -0.004 / -0.020 |
| 6 mm | 6.012 / 6.000 | 6.027 / 6.019 | -0.007 / -0.027 |
| 10 mm | 10.015 / 10.000 | 10.032 / 10.023 | -0.008 / -0.032 |
| 18 mm | 18.018 / 18.000 | 18.039 / 18.028 | -0.010 / -0.039 |
| 30 mm | 30.021 / 30.000 | 30.048 / 30.035 | -0.014 / -0.048 |
| 50 mm | 50.025 / 50.000 | 50.059 / 50.043 | -0.018 / -0.059 |
| 80 mm | 80.030 / 80.000 | 80.078 / 80.059 | -0.029 / -0.078 |
| 120 mm | 120.035 / 120.000 | 120.101 / 120.079 | -0.044 / -0.101 |
| 180 mm | 180.040 / 180.000 | 180.133 / 180.108 | -0.068 / -0.133 |
| 250 mm | 250.046 / 250.000 | 250.169 / 250.140 | -0.094 / -0.169 |
| 1/4 in | 0.25059 / 0.25000 | 0.25126 / 0.25091 | -0.00031 / -0.00126 |
| 1/2 in | 0.50071 / 0.50000 | 0.50154 / 0.50110 | -0.00039 / -0.00154 |
| 3/4 in | 0.75083 / 0.75000 | 0.75189 / 0.75138 | -0.00055 / -0.00189 |
| 1 in | 1.00083 / 1.00000 | 1.00189 / 1.00138 | -0.00055 / -0.00189 |
| 1-1/2 in | 1.50098 / 1.50000 | 1.50232 / 1.50169 | -0.00071 / -0.00232 |
| 2 in | 2.00118 / 2.00000 | 2.00283 / 2.00209 | -0.00091 / -0.00283 |
H7/u6: force
| Size | Hole H7 | Shaft u6 | Fit |
|---|---|---|---|
| 1 mm | 1.010 / 1.000 | 1.024 / 1.018 | -0.008 / -0.024 |
| 3 mm | 3.010 / 3.000 | 3.024 / 3.018 | -0.008 / -0.024 |
| 6 mm | 6.012 / 6.000 | 6.031 / 6.023 | -0.011 / -0.031 |
| 10 mm | 10.015 / 10.000 | 10.037 / 10.028 | -0.013 / -0.037 |
| 18 mm | 18.018 / 18.000 | 18.044 / 18.033 | -0.015 / -0.044 |
| 30 mm | 30.021 / 30.000 | 30.061 / 30.048 | -0.027 / -0.061 |
| 50 mm | 50.025 / 50.000 | 50.086 / 50.070 | -0.045 / -0.086 |
| 80 mm | 80.030 / 80.000 | 80.121 / 80.102 | -0.072 / -0.121 |
| 120 mm | 120.035 / 120.000 | 120.166 / 120.144 | -0.109 / -0.166 |
| 180 mm | 180.040 / 180.000 | 180.235 / 180.210 | -0.170 / -0.235 |
| 250 mm | 250.046 / 250.000 | 250.313 / 250.284 | -0.238 / -0.313 |
| 1/4 in | 0.25059 / 0.25000 | 0.25146 / 0.25110 | -0.00051 / -0.00146 |
| 1/2 in | 0.50071 / 0.50000 | 0.50173 / 0.50130 | -0.00059 / -0.00173 |
| 3/4 in | 0.75083 / 0.75000 | 0.75213 / 0.75161 | -0.00079 / -0.00213 |
| 1 in | 1.00083 / 1.00000 | 1.00240 / 1.00189 | -0.00106 / -0.00240 |
| 1-1/2 in | 1.50098 / 1.50000 | 1.50299 / 1.50236 | -0.00138 / -0.00299 |
| 2 in | 2.00118 / 2.00000 | 2.00417 / 2.00343 | -0.00224 / -0.00417 |
Inch drawings: the ANSI B4.1 classes
On inch drawings the same jobs are usually done by the ANSI B4.1 fit classes, which are tabulated in thousandths of an inch rather than derived from ISO. The families line up by purpose, not number for number. Running and sliding fits RC1 to RC9 cover the clearance end: RC1 and RC2 are the close sliding fits that play the role of H7/g6, RC3 to RC5 are the precision and close running fits near H8/f7, RC6 and RC7 sit near H9/d9, and RC8 and RC9 are loose running fits like H11/c11. Locational clearance fits LC1 to LC11 start where H7/h6 does and open up from there. Locational transition fits LT1 to LT6 span the range of H7/k6 and H7/n6. Locational interference fits LN1 to LN3 correspond to H7/p6, and force and shrink fits FN1 to FN5 run from light drive through the range of H7/s6 and H7/u6 to the heaviest shrink fits.
If a print calls an ANSI class, work to the ANSI table. If it calls an ISO class on an inch part, the inch rows above and the calculator convert the ISO limits for you. Anything a fit does not control, such as a chamfer or a non-mating length, usually falls back to the title block or to ISO 2768 general tolerances.
Holding IT6 and IT7 takes reaming, fine boring or grinding, shafts from CNC turning or grinding, and a way to prove it: bore gauges and micrometers on the floor, or CMM inspection for the report.
Frequently asked questions
- What are the ISO preferred fits?
- ISO 286-1 recommends a short list of hole and shaft pairs so that shops can stock one set of reamers, plug gauges and ring gauges instead of hundreds. The ten hole-basis fits here run from loose running (H11/c11) to force (H7/u6). Each has a shaft-basis twin, such as G7/h6 for H7/g6, with the same clearances.
- How do I read the clearance table?
- Each cell gives the maximum and minimum clearance in micrometers for that fit and size. Positive numbers are clearance and negative numbers are interference. H7/g6 at 30 mm reads +41 / +7: the loosest pair has 0.041 mm of clearance and the tightest 0.007 mm. H7/s6 at 30 mm reads -14 / -48: always interference, from 0.014 to 0.048 mm.
- Why is H7/p6 not an interference fit at 1 and 3 mm?
- Up to 3 mm the published p deviation is +6 micrometers while the H7 hole is 10 micrometers wide, so the loosest pair still has 4 micrometers of clearance. From 3 to 18 mm the pair is line to line at its loosest, and above 18 mm it is always interference. The chart computes each size, so it shows the fit you will actually get.
- Where do these numbers come from?
- They are computed when the page is built from the ISO 286-1 formulas (IT grades from the tolerance factor i, fundamental deviations by letter), rounded the way the standard rounds, with the published table value used wherever the table differs. The module is tested cell by cell against the published tables. Confirm critical limits against ISO 286-2 or ASME B4.2.
- Do inch drawings use these fits?
- Inch drawings usually call ANSI B4.1 classes instead: RC for running and sliding, LC for locational clearance, LT for transition, LN for locational interference and FN for force and shrink fits. They do the same jobs as the ISO fits but are tabulated separately, so the numbers differ. The inch rows here are the ISO fits converted to inches, useful when a metric-designed part is made in an inch shop.
