● Bolt connections in electrotechnical installations always require a torque adapted to the bolt diameter.
● A torque wrench sets the tightening torque in advance to match the bolt size.
● Correct torque prevents mechanical failure and ensures electrical safety. ⚡
● The tightening torque for M6 bolts is 8 Newton-meters (Nm).
● The tightening torque for M8 bolts is 20 Nm.
● The tightening torque for M10 bolts is 40 Nm. 🔧
● The tightening torque for M12 bolts is 70 Nm.
● The tightening torque for M16 bolts is 120 Nm.
● The control torque is approximately 80 percent of the recommended torque. 📏
● The control torque for M6 bolts is 6 Nm.
● The control torque for M8 bolts is 16 Nm.
● The control torque for M10 bolts is 32 Nm.
● The control torque for M12 bolts is 55 Nm.
● The control torque for M16 bolts is 96 Nm. ⚙️
STANDARDS AND MATERIAL CONDITIONS
● The tightening torques are derived from DIN 43673 (Deutsches Institut für Normung, German Institute for Standardization).
● They are also derived from VDE 0220 T2 (Verband der Elektrotechnik, German Association for Electrical, Electronic and Information Technologies).
● They are also derived from NEN 3062:1957 (Nederlands Normalisatie-instituut, Netherlands Standardization Institute). 📚
● The rules apply to copper connections with a conductor cross-section of 4 square millimeters or larger.
● The bolts must be zinc-coated steel of quality class 8.8 or higher, including classes 10.9 and 12.9.
● The tightening is always performed without lubricants. 🛠️
● Spring washers made of steel according to DIN 127B are mandatory for all bolt connections.
SPANNER SIZES
● The spanner width “s” corresponds to the nominal bolt size.
● The dimensions are fixed in NEN 2283:1981 (Netherlands Standardization Institute).
● NEN 2283 defines internal widths for machine parts, fittings, and related components. 📐
● The spanner must always match the nominal bolt size exactly.
● The correct spanner ensures proper force distribution.
● The correct spanner also prevents deformation of the bolt head. 🔩
LEARNING OBJECTIVE
● The reader acquires technical knowledge of tightening torques in electrotechnical installations.
● The reader understands the normative basis defined by DIN, VDE, and NEN standards.
● The reader learns the numerical torque values for bolts M6, M8, M10, M12, and M16. 📊
● The reader understands the concept of control torque at 80 percent of the recommended torque.
● The reader recognizes the importance of bolt quality class and absence of lubricants.
● The reader identifies the link between correct spanner size and reliable bolt connection. 🧩
My Diary - Leonardo Cardillo 