Dowel pins
A standard dowel pin is made oversize: a nominal Ø6 m6 pin measures 6.004–6.012 mm, so in an H7 reamed hole (6.000–6.012 mm) it runs from 12 µm interference to 8 µm clearance, a light press in practice. Enter a nominal diameter for the pin’s limits (ISO 2338 m6 or h8, ISO 8734 hardened m6), its fixed hole, and the fit a mating hole gives on it.
The pin and both holes are drawn to scale with their tolerance zones side by side, so you can see which hole class lets the mating part lift off and which one grips.
ISO 2338 m6 · Ø6 · clearance is hole minus pin, so a negative number is interference.
- H7 fixed hole on the m6 pin: transition fit
- −12 to +8µm
- F7 mating hole on the pin
- …
- Pin Ø m6, max / min
- Fixed hole Ø H7, max / min
- End chamfer c ≈ (both ends, ≈15° to the axis)
- 1.2mm
The pin standards set the pin’s class only. The hole classes are shop practice: an H7 hole on an m6 pin is a transition fit (a light press), and a mating hole has to clear the pin’s largest size to lift off freely, which F7 does not quite do at every size.
How it’s calculated
Each limit is the nominal plus its ISO 286 deviation. The largest clearance is the hole's upper limit less the shaft's lower, the smallest the hole's lower less the shaft's upper: both positive is a clearance fit, both negative an interference, one of each a transition.
| Standard | Nominal | Pin tol | Hole tol | Pin max/min | Hole max/min | Unit |
|---|---|---|---|---|---|---|
| ISO 2338 | 1 | m6 | H7 | 1.008 / 1.002 | 1.010 / 1.000 | mm |
| ISO 2338 | 1.5 | m6 | H7 | 1.508 / 1.502 | 1.510 / 1.500 | mm |
| ISO 2338 | 2 | m6 | H7 | 2.008 / 2.002 | 2.010 / 2.000 | mm |
| ISO 2338 | 2.5 | m6 | H7 | 2.508 / 2.502 | 2.510 / 2.500 | mm |
| ISO 2338 | 3 | m6 | H7 | 3.008 / 3.002 | 3.010 / 3.000 | mm |
| ISO 2338 | 4 | m6 | H7 | 4.012 / 4.004 | 4.012 / 4.000 | mm |
| ISO 2338 | 5 | m6 | H7 | 5.012 / 5.004 | 5.012 / 5.000 | mm |
| ISO 2338 | 6 | m6 | H7 | 6.012 / 6.004 | 6.012 / 6.000 | mm |
| ISO 2338 | 8 | m6 | H7 | 8.015 / 8.006 | 8.015 / 8.000 | mm |
| ISO 2338 | 10 | m6 | H7 | 10.015 / 10.006 | 10.015 / 10.000 | mm |
| ISO 2338 | 12 | m6 | H7 | 12.018 / 12.007 | 12.018 / 12.000 | mm |
| ISO 2338 | 16 | m6 | H7 | 16.018 / 16.007 | 16.018 / 16.000 | mm |
| ISO 2338 | 20 | m6 | H7 | 20.021 / 20.008 | 20.021 / 20.000 | mm |
| ISO 2338 | 1 | h8 | H8 | 1.000 / 0.986 | 1.014 / 1.000 | mm |
| ISO 2338 | 2 | h8 | H8 | 2.000 / 1.986 | 2.014 / 2.000 | mm |
| ISO 2338 | 3 | h8 | H8 | 3.000 / 2.986 | 3.014 / 3.000 | mm |
| ISO 2338 | 4 | h8 | H8 | 4.000 / 3.982 | 4.018 / 4.000 | mm |
| ISO 2338 | 5 | h8 | H8 | 5.000 / 4.982 | 5.018 / 5.000 | mm |
| ISO 2338 | 6 | h8 | H8 | 6.000 / 5.982 | 6.018 / 6.000 | mm |
| ISO 2338 | 8 | h8 | H8 | 8.000 / 7.978 | 8.022 / 8.000 | mm |
| ISO 2338 | 10 | h8 | H8 | 10.000 / 9.978 | 10.022 / 10.000 | mm |
| ISO 2338 | 12 | h8 | H8 | 12.000 / 11.973 | 12.027 / 12.000 | mm |
| ISO 2338 | 16 | h8 | H8 | 16.000 / 15.973 | 16.027 / 16.000 | mm |
| ISO 2338 | 20 | h8 | H8 | 20.000 / 19.967 | 20.033 / 20.000 | mm |
| ISO 8734 | 1 | m6 | H7 | 1.008 / 1.002 | 1.010 / 1.000 | mm |
| ISO 8734 | 2 | m6 | H7 | 2.008 / 2.002 | 2.010 / 2.000 | mm |
| ISO 8734 | 3 | m6 | H7 | 3.008 / 3.002 | 3.010 / 3.000 | mm |
| ISO 8734 | 4 | m6 | H7 | 4.012 / 4.004 | 4.012 / 4.000 | mm |
| ISO 8734 | 5 | m6 | H7 | 5.012 / 5.004 | 5.012 / 5.000 | mm |
| ISO 8734 | 6 | m6 | H7 | 6.012 / 6.004 | 6.012 / 6.000 | mm |
| ISO 8734 | 8 | m6 | H7 | 8.015 / 8.006 | 8.015 / 8.000 | mm |
| ISO 8734 | 10 | m6 | H7 | 10.015 / 10.006 | 10.015 / 10.000 | mm |
| ISO 8734 | 12 | m6 | H7 | 12.018 / 12.007 | 12.018 / 12.000 | mm |
| ISO 8734 | 16 | m6 | H7 | 16.018 / 16.007 | 16.018 / 16.000 | mm |
| ISO 8734 | 20 | m6 | H7 | 20.021 / 20.008 | 20.021 / 20.000 | mm |
Which hole class does each part of a doweled joint take?
A doweled joint has two holes. The pin is pressed into the fixed part, in the reamed hole class the table lists against the pin; the mating part is the one that comes off, and its hole has to clear the pin’s largest size so it can lift off without driving the pin out. The pin standards set the pin’s class only, so the mating hole class is shop practice: this page offers H7, G7, F7, E8 and works out what each really gives against the pin. The tighter classes can still touch or grip the largest pins, which is why the drawing shows the zones and not just the class.