Practical advice
- Only apply the power tool to the screw/nut when the tool is switched off. Rotating tool inserts can slip off.
The torque depends on the impact duration. The maximum achieved torque results from the sum of all individual torques achieved through impact. Maximum torque is achieved after an impact duration of 6–10 seconds. After this duration, the tightening torque is increased only minimally.
The impact duration is to be determined for each required tightening torque. The tightening torque actually achieved should always be checked with a torque wrench.
Screw applications with hard, spring-loaded or soft seats
When the achieved torques in an impact series are measured during a test and transferred into a diagram, the result is the curve of a torque characteristic. The height of the curve corresponds to the maximum achievable torque, and the steepness indicates the duration in which this is achieved.
A torque characteristic depends on the following factors:
- Strength properties of the screws/nuts
- Type of backing (washer, disc spring, seal)
- Strength properties of the material being screwed/bolted together
- Lubrication conditions at the screw/bolt connection
The following application cases result accordingly:
- A hard seat is a metal-to-metal screw application which uses washers. After a relatively short impact duration, the maximum torque is achieved (steep characteristic curve). An unnecessarily long impact duration only causes damage to the machine.
- A spring-loaded seat is also a metal-to-metal screw application but uses spring washers, disc springs, studs or screws/nuts with conical seats. It is also called a spring-loaded seat when extensions are used.
- A soft seat is a screw application of e.g. metal on wood or a screw application that uses lead washers or fibre washers as backing.
For a spring-loaded seat, as well as for a soft seat, the maximum tightening torque is lower than for a hard seat. A much longer impact duration is also required.
Guide values for maximum screw tightening torques
Figures given in Nm; calculated from the tensional cross-section; utilization of the yield point: 90% (with friction coefficient µtotal = 0.12). As a control measure, always check the tightening torque with a torque wrench.
Property Classes according to DIN 267 | Standard Screws/Bolts | High-strength Bolts | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
3.6 | 4.6 | 5.6 | 4.8 | 6.6 | 5.8 | 6.8 | 6.9 | 8.8 | 10.9 | 12.9 | |
M6 | 2.71 | 3.61 | 4.52 | 4.8 | 5.42 | 6.02 | 7.22 | 8.13 | 9.7 | 13.6 | 16.2 |
M8 | 6.57 | 8.7 | 11 | 11.6 | 13.1 | 14.6 | 17.5 | 19.7 | 23 | 33 | 39 |
M10 | 13 | 17.5 | 22 | 23 | 26 | 29 | 35 | 39 | 47 | 65 | 78 |
M12 | 22.6 | 30 | 37.6 | 40 | 45 | 50 | 60 | 67 | 80 | 113 | 135 |
M14 | 36 | 48 | 60 | 65 | 72 | 79 | 95 | 107 | 130 | 180 | 215 |
M16 | 55 | 73 | 92 | 98 | 110 | 122 | 147 | 165 | 196 | 275 | 330 |
Tips
Before screwing larger, longer screws into hard materials, it is advisable to pre-drill a pilot hole with the core diameter of the thread to approx. 2/3 of the screw length.
Note: Ensure that no metal particles enter the power tool.
Recommendations for optimal handling of the battery
Protect the battery against moisture and water.
Only store the battery only within a temperature range of -20 to 50 °C. Do not leave the battery in your car in the summer, for example.
Occasionally clean the ventilation slots on the battery using a soft brush that is clean and dry.
A significantly reduced operating time after charging indicates that the battery has deteriorated and must be replaced.
Follow the instructions on correct disposal.