Hi Replacing/updating worn 13A wall sockets and light switch plates on late 1960s system and wanting to use original pattress box where poss, how do I overcome the different threads sizes 4BA in the box and 3.5mm when the old screw length is to short. Are 35mm box best for MK if replacing.
If you contact a local fixings company, they should stock or be able to source you 4BA screws to whatever length you require.
To re-tap try this: http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=48272&id=94356 Short 3.5mm : http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=48670&id=12657