HM390-ND - M4 Self Captivating Screw insert Comes unseated

I’m using the Hammond HM 390-ND on my product to enclose a circuit card and have found several of the units have M4 Self Captivating Screws that come unseated and spin inside the plastic they were inserted into. Wondering if I’m doing something wrong. I ordered 50 and am using 32. I’ve had 3 out of the 32 with this condition. Two of them occured as I was screwing the lid onto the box - the screw would get real tight then you could neither back it out or insert it fully because the screw insert breaks away from the plastic. I’m using a power drill with very light torque setting so doubt that would be the issue.

Also have a side question - does the flat side of the gasket face the bottom lid when assembling (with the round side fitting into the channel face down?


If I’m understanding correctly, you’re saying that the metal inserts pressed into one enclosure half are breaking loose before the corresponding fastener for securing the lid seats fully? That could be caused by a number of things–excessively long screw, an insert that was incompletely threaded, cross-threading, debris in the bottom of the hole, or plastic displaced when the insert was pressed in flowing back up into the insert. Maybe something else… I’d pull the assembly apart, take a close look at it, and see if an explanation presents itself. Insofar as many of these possibilities would constitute a deficiency in manufacture, you may also want to contact customer service for replacements if the issue doesn’t turn out to be related to your assembly process.

As for the gasket, it would appear to me that avoiding twists along its length would be of greater concern than which face is presented to which half of the enclosure.

Thank you for the information. I can rule out excessively long screw as the screws are supplied with the enclosure . I will take the assemblies apart and try to see the root cause amongst the others and contact customer service if it is something not associated with the assembly process itself.