Clean the threads thoroughly and reassemble with blue LocTite. Problem solved.
While thread lockers certainly aren't "fool proof" there are several application tips that you can use to increase your "batting average".
• You've got to remove
ALL the oil and grease from
BOTH threads. The thorough cleaning must be done on both male and female
mating threads.
• This calls for a
highly astringent thinner like lacquer thinner, spray carb cleaner, spray brake cleaner, etc. Some things like rubbing alcohol are not astringent enough and may take several repeated applications. Others, like lighter fluid, seem to have an oil base that leaves as much oil as it removes.
• Use of
compressed air to blow both parts clean and dry really speeds up the process. Otherwise you are far better off to allow the thinner to dry (evaporate) over-night in a warm place before assembly. Assembly too quickly leaves thinner in the threads, which simply thins out the thread locker.
• One (hopefully both) of the parts should have exposed
steel, brass or aluminum. LocTite is activated by metal ions in the absence of air. (If your LocTite tip keeps clogging, then stop touching the tip to the metal screw and stand the tube upright after use.)
• Tightening the fastener pair also seems to help. Figure out a way to apply some torque to the screw and your thread locker will work even better.
Hope this helps.