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In IEC 60335-1 cl 28.3
/ ?6 B% L; a6 U+ Q( l- t% A6 TSpace-threaded (sheet metal) screws shall only be used for electrical connection if they clamp the 1 \* O) Y! f" `9 l1 X
parts together.
, K$ j; S" B- q+ `! a! eThread-cutting (self-tapping)screws shall only be used for electrical connections if they generate a full form standard machine screw thread. Such screws shall not be used if they are likely to be operated by the user or installer.
7 h x/ g' ~" zThread-cutting and space-threaded screws may be used in connections providing earthing continuity provided it is unnecessary to disturb the connection in normal use and at least two screws are used for each connection.3 f, N. q5 R$ s7 \% `
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In IEC 60598-1 cl 7.2.1 Provision for earthing- F& V! j2 H( V- P; S: n
Self-tapping screws may be used to provide earthing continuity, provided that it is not necessary to disturb the connection in normal use and that at least two screws are used for each connection.
$ I; q9 Y: `. o. s- ?Thread-forming screws may be used to provide earthing continuity if they comply with the requirements for screw terminals./ `9 Q/ h8 H2 N. d
A thread forming screw used in a groove of a metallic material could provide earth continuity for a luminaire if all the tests required withing IEC 60598-1 regarding earthign connection were passed.2 O4 ]8 b; @! P
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In IEC 60950-1 cl 3.1.8 Self-tapping and space thread screws5 G% I+ z& R. S. w
Spaced thread (sheet metal) screws shall not be used for the connection of current-carrying parts, unless they clamp these parts directly in contact with each other and are provided iwth a suitable means of locking.
Z1 L, E. J# KSelf-tapping (thread-cutting or thread-forming) screws shall not be used for the electrical connection of current-carrying parts, unless they generate a full form standard maching screw thread. Moreover, such screws shall not be used if they are operated by the user or installer unless the thread is formed by a swaging action.1 w* O2 [/ o/ g+ d
IEC 60950-1 cl 2.6.5.7 Screws for protective bonding, ~# W0 ?3 @. e+ L
Self-tapping (thread-cutting and thread-forming) and spaced thread (sheet metal) screws are permitted to provide protective bonding but it shall not be necessary to disturb the connection during servicing.3 ]# b. r V. s% R& W5 z, Q, ?; J2 r
At least two screws shall be used for each connection. However, it is permitted to use a single self-tapping screw provided that the thickness of the metal part at the point where the screw is threaded into it is a minimum of 0,9mm for a screw of the thread-forming type and 1,6mm for a screw of the thread-cutting type. |
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