I recently had to remove the cutting blade from my self propelled petrol mower (Briggs & Stratton) to enable me to replace the belt drive, great no problem here and I greased the retaining bolt and it's thread on replacing the blade - now the retaining bolt keeps coming loose and the blade comes off when I run it, why ? because I tighten the bolt as tight as I can manage

PeteH, May 2012

Check that the blade boss is not loose on the shaft (key sheared). If ok, replace the spring washer under the bolt head.

FYI - at the factory, they put non-hardening thread-lock on the bolt. Clean off the grease, make sure that it's clean, but dry, then use Loctite or similar.

Make sure it's the NON-HARDENING type. Get this wrong, and you might as well weld it on!

phil_saunders(a)bigfoot.com

Phil Saunders, May 2012