Metric Dowel Pin Press Fit Calculator
Estimate ISO dowel pin interference, hole and pin tolerance overlap, contact pressure, assembly force, thermal fit allowance, and hub stress for metric locating pins.
📊Press Fit Results
| Typical fit | Pin band | Hole band | Expected use | Calculator note |
|---|---|---|---|---|
| Slip or service | h6 | H7 or K7 | Removable locating dowel | May show zero pressure if clearance exists |
| Light press | m6 | H7 | Fixture plates, inspection nests | Often installable with light arbor pressure |
| Medium press | n6 | H7 | Machine plates, repeat location | Check thin wall hoop stress |
| Heavy press | p6 | H7 or M7 | Die shoes, permanent locators | Thermal assist is usually preferred |
| Diameter step | IT6 approx. | IT7 approx. | m6 shaft zone | H7 hole zone |
|---|---|---|---|---|
| 3 to 6 mm | 8 µm | 12 µm | +4 to +12 µm | 0 to +12 µm |
| 6 to 10 mm | 9 µm | 15 µm | +6 to +15 µm | 0 to +15 µm |
| 10 to 18 mm | 11 µm | 18 µm | +7 to +18 µm | 0 to +18 µm |
| 18 to 30 mm | 13 µm | 21 µm | +8 to +21 µm | 0 to +21 µm |
| Material pair | Pin E | Housing E | Housing yield | Fit caution |
|---|---|---|---|---|
| Hardened steel into carbon steel | 210 GPa | 200 GPa | 250 MPa | Good general press fit reference |
| Steel into aluminum 6061 | 210 GPa | 69 GPa | 240 MPa | More elastic opening, higher thermal growth |
| Steel into brass | 210 GPa | 100 GPa | 150 MPa | Use lighter interference for small edges |
| Stainless into stainless | 193 GPa | 193 GPa | 215 MPa | Lubrication matters because galling risk rises |
| Steel into gray cast iron | 210 GPa | 110 GPa | 170 MPa | Avoid shock pressing brittle bosses |
| Thermal assembly method | Rule of thumb | Benefit on 10 mm pin | Practical note |
|---|---|---|---|
| Warm steel housing 50 °C | 12 ppm/C | 6 µm hole growth | Often enough for light m6/H7 fits |
| Warm aluminum housing 50 °C | 23 ppm/C | 12 µm hole growth | Aluminum gains clearance quickly |
| Chill steel pin 50 °C | 11 ppm/C | 6 µm pin shrink | Combine with housing heat for heavy fits |
| Service heat difference | CTE mismatch | Can add or remove grip | Review hot tooling and cryogenic fixtures |
Metric dowel pins is used to create a mechanical bond between two component that contain a hole through the use of an interference fit. An interference fit is created by the fact that the metric dowel pin is slightly larger than the diameter of the hole into which it is to be pressed. When the pin is pressed into the hole, the pin and the hole experience slight compression and expansions, respectively.
These movements creates radial pressure on the pin, which creates the friction between the dowel pin and the hole that ensures that the dowel pin will remain in place. If the interference fit between the dowel pin and the hole is too loose, the pin will not remain in the hole. If the interference fit is too tight, however, it is possible that the workpiece will crack when you press the dowel pin into the workpiece.
How Metric Dowel Pins Fit Into Holes
Selecting the correct ISO metric fit is a necessary process prior to inserting the dowel pin into the workpiece. Each ISO designation contain specific codes that relate to the size of the holes and the size of the dowel pins. For example, an H7 designation relates to the size of the hole, while an m6 designation relates to the size of the dowel pin.
An m6 dowel pin that is inserted into an H7 hole creates a “light” press fit. A light press fit is often used for components that may need to be disassembled in the future. An n6 and p6 dowel pin, however, create a heavier interference fit with the hole.
These heavier interference fits is often used for components that are to remain in place, such as heavy die sets, where it is necessary to prevent the dowel pin from moving within the workpiece due to vibration that may occur during operation of the workpiece. The materials from which the dowel pin and the workpiece is made will impact the way in which the dowel pin and the workpiece interact with one another. Metals have elasticity ratings, and the elasticities of metals change the amount in which the metal compress during the insertion of the dowel pin.
For instance, if you press a hardened steel dowel pin into a block of carbon steel, the resulting assembly will be stiff due to the stiffness of the metals. However, if the same hardened steel dowel pin is pressed into a block of aluminum 6061 metal, the aluminum will stretch more than the carbon steel. As a result, the aluminum will exert less pressure on the dowel pin than the carbon steel block.
The yield strength of the metal workpiece must be considered in relation to the pressure of the metric dowel pin. Should the hoop stress of the dowel pin exceed the yield strength of the workpiece metal, the workpiece will deform. Several variable will impact the assembly of the dowel pin.
For instance, the polished nature of the dowel pin and the use of assembly oil will require less force to insert the pin than a dry dowel pin. Furthermore, the lead chamfer on the end of the dowel pin assists in the even insertion of the pin into the workpiece hole. Without the lead chamfer, more force will be required to insert the pin, as the pin could enter the workpiece hole at an angle.
Should the pin enter the workpiece at an angle, it will be difficultly to straighten the pin once it enters the workpiece. The temperature of the workpiece or the dowel pin can be utilized during the assembly of the dowel pin. If the interference fit of the dowel pin into the workpiece is very heavy, you can heat the workpiece or chill the dowel pin prior to insertion into the workpiece.
As the workpiece is heated, it expand; as the dowel pin is chilled, it contracts. Once the workpiece and the dowel pin reach room temperature, the interference fit between the components will return to its original state. Using temperature variables is helpful in workpieces with thin walls.
Thin walled workpieces may not be able to withstand the cold press that is required to insert the dowel pin into the thin-walled workpiece. Using too much force on thin-walled workpieces will deform the thin-walled workpiece and stretch it permanent. The stretched workpiece will no longer securely hold the metric dowel pin.
Its going to be hard to fix if you use too much force. You should of checked the material first.
