Extra high strain relief

M40 connectors


A company specialising in heat treatment of metals focuses on monitoring and servic-
ing pipelines in the oil and gas industry. The company was looking for a connector for
power supply and signal transmission for welding control systems. HUMMEL AG de-
veloped a customised solution by modifying the M 40 power connector from the stan-
dard configuration (4 signal contacts and 3+PE) to 4 signal contacts and 4 power
contacts. In addition, the connector was given a "one-turn" thread for faster connec-
Two further requirements for the new connector were identified in praxis:

  • The "one-turn" thread worked well with the cable connector, but the forces required to insert it into the panel connector were found to be too high.
  • Combined with a heavy cable on the connector, the customer felt the possibility of miscoding the connector when mating was too high


To overcome the high forces when plugging into the chassis connector, the corre-
sponding female part was provided with a longer thread. This allows the assemblers
to "pull" the connectors together by turning the knurled nut instead of pushing both
parts into each other. To increase security against miscoding, HUMMEL redesigned the
outer contour of the insulating inserts and improved the coding options. During the
successful testing of the improved coding, the customer expressed the wish to have a
possibility to distinguish between the "old" and "new" condition of the insulating in-
sert. HUMMEL realised this distinction by using orange plastic, which is easily distin-
guishable from the blue colour of the first product design.


  • Extra strain relief
  • Die cast housing
  • One-turn thread
  • Extra long thread
  • Customized insert colour
M40 Power  
Number of poles 4+4
Nominal current [A] 70
Nominal voltage [V] 60
Strain relief [kg] 180