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| | | Coefficient of friction (jl/) | | |
| | | The coefficient of friction depend on a number of factors. The most important are: SURFACE FINISH The surface must not be too smooth. If it is, the influence of impurities can be great. A good turning operation is often better than grinding. CLEANLINESS It is very important that the surfaces are well cleaned. Professional grease on the surfaces will drastically reduce the coefficient of friction. A thin oil will however only reduce the coefficient of friction with about 0,03 ¿7. MATERIAL The coefficient of friction varies depending on the materials of the contact surfaces, see table. | | |
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| | | Recommended surface finish, shaft/hub | | |
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| | | Ra max 3,0 (//m) Ra min 1,0 (um) | | |
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| | | | | | | | | | | | | | | | | | Value of y for well cleaned contact surfaces | | | | steel | stainless steel | | | | steel | cast iron | aluminium | aluminium bronze | stainless steel | stainless steel | | | | | | | | | | | | | | | | | | | | | | |
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| | | Surface pressure and torque | | |
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| | | If the surface pressure is too low, a metallic contact between the surfaces will not be created because of oxide layers. If the surface pressure is too high, plastic deformation can occur and the friction will decrease dramatically. The hydraulic ETP principle gives a surface pressure within the right range, which is also utmost even around and along the contact area. The surface pressure from the ETP connections (not ETP-HYLOC or ETP-IMPRESS) is at the recommended tightening torque: ps = approx. 90 N/mm2. pH = approx. 70 N/mm2. By increasing the surface pressure the transmittable torque can be increased, see table. | | |
| | | Max. tightening torque (screw quality 12.9)
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| | | | | | | | | | | **M5 | **M6 | **M8 | | | | 10 Nm | 17 Nm | 40 Nm | | | | | | | | | | |
| | | *M4 | | |
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| | | 5 Nm | | |
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| | | If the tightening torque is increased the transmittable torque wiil increase. *) Valid for ETP-MINI. Transmittable torque, Tr, is increased by 20 %. **) Valid for ETP-CLASSIC. Transmiitable forque, Tr, is increased by 25 %. This effect can only be used if the operating temperature < the mounting temperature. | | |
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| | | Tolerances | | |
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| | | | | | | | | | | Change of torque when ETP-CLASSIC is mounted on: | | | | h9 shaft | h8 shaft | k6 shaft | | | | - 25 % | acc. to techn. data | + 20 % | | | | | | | | | | |
| | | Recommended tolerances for shaft and hub are given under the section for each product. If the tolerance differs from these so the play between the contact surfaces is increased. The surface pressure and the torque will decrease. The opposite is valid for decreased play. See example in the table. | | |
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| | | | | | | | | | | | | | | | | | Shaft tolerances in //m (upper/lower limits) | | Hub tolerances in //m (upper/lower limits) | | | | Shaft dia. | k6 | h7 | h8 | h9 | h10 | | Shaft dia. | H7 | H8 | | | | (3) - 6 | +9/+1 | 0/-12 | 0/-18 | 0/-30 | 0/-48 | | (10) - 18 | +18/0 | +27/0 | | | | (6) - 10 | +10/+1 | 0/-15 | 0/-22 | 0/-36 | 0/-58 | | (18) - 30 | +21/0 | +33/0 | | | | (10) - 18 | +12/+1 | 0/-18 | 0/-27 | 0/-43 | 0/-70 | | (30) - 50 | +25/0 | +39/0 | | | | (18) - 30 | +15/+2 | 0/-21 | 0/-33 | 0/-52 | 0/-84 | | (50) - 80 | +30/0 | +46/0 | | | | (30) - 50 | +18/+2 | 0/-25 | 0/-39 | 0/-62 | 0/-100 | | (80) - 120 | +35/0 | +54/0 | | | | (50) - 80 | +21/+2 | 0/-30 | 0/-46 | 0/-74 | 0/-120 | | (120) - 180 | +40/0 | +63/0 | | | | (80) - 120 | +25/+3 | 0/-35 | 0/-54 | 0/-87 | 0/-140 | | (180) - 250 | +46/0 | +72/0 | | | | (120) - 180 | +28/+3 | 0/-40 | 0/-63 | 0/-100 | 0/-160 | | (250) - 315 | +52/0 | +81/0 | | | | (180) - 250 | +33/+4 | 0/-46 | 0/-72 | 0/-115 | 0/-185 | | | | | | | | | | | | | | | | | | |
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