NEVER USE WD40 as a lubricant. It is a lousy lubricant, was never designed to lubricate and basically sucks for that purpose. WD stands for "water displacement." Here's a discussion: http://yarchive.net/chem/wd40.html

The recommended lubricant for the RSK Mk1 is MILITEC-1 http://www.militec1.com/
They will send you a free sample which will last years for most folks.