Thank you Legh and Z and Mike.  Mike, your entry appeared just before I submitted this reply, so sorry about the repetition!  The socket in my garden is an MK so I don't doubt the quality.  However it does go for about four months over the winter without use, being subjected to some large temperature and humidity swings which it will experience to a limited degree, even though its inside an IP66 enclosure.  Then in the spring out come all those garden tools that have been in that damp garage with the plugs all covered in cobwebs and more serious, a microscopic layer of corrosion on the pins.  The plug may have even been dropped on the garden path leaving a some damage on the corner of the earth pin where it contacts the socket shutter.  I suggest that any or all of these conditions could give rise to a less than smooth mating of plug and socket!  I had a look in my garage and found this extreme example which appears to have all of the above, plus some overspray from some white paint for a radiator cover! 





I must admit, I had never given all this such serious thought before but I will now be checking and cleaning if required all my garden equipment plugs.  I must stress these 230v items are in the minority in my garden, most things are of the much safer battery variety.


I think my original question about lubrication was probably an attempt to treat the symptoms rather than find and sort out the cause!

Thank you Legh and Z and Mike.  Mike, your entry appeared just before I submitted this reply, so sorry about the repetition!  The socket in my garden is an MK so I don't doubt the quality.  However it does go for about four months over the winter without use, being subjected to some large temperature and humidity swings which it will experience to a limited degree, even though its inside an IP66 enclosure.  Then in the spring out come all those garden tools that have been in that damp garage with the plugs all covered in cobwebs and more serious, a microscopic layer of corrosion on the pins.  The plug may have even been dropped on the garden path leaving a some damage on the corner of the earth pin where it contacts the socket shutter.  I suggest that any or all of these conditions could give rise to a less than smooth mating of plug and socket!  I had a look in my garage and found this extreme example which appears to have all of the above, plus some overspray from some white paint for a radiator cover! 





I must admit, I had never given all this such serious thought before but I will now be checking and cleaning if required all my garden equipment plugs.  I must stress these 230v items are in the minority in my garden, most things are of the much safer battery variety.


I think my original question about lubrication was probably an attempt to treat the symptoms rather than find and sort out the cause!