Ok here is the straight dope on the loctite threadlockers, They are currently on sale in the May 2012 Enco flyer.
222MS Threadlocker, low strength/purple for locking sealing screws
242 Threadlocker, medium strength/removable/blue locks seals nuts,bolts, screws and fittings
262 Threadlocker, permanent strength/red heavy duty use on bolts and studs
271 Threadlocker, High strength/red Locks and seal, plugs, bolts and nuts
290 Threadlocker, Wicking grade/green locks and seals pre-assembled fasteners to eliminate vibration and corrosion
Loctite also has a plastic to metal threadlocker it is 425 Assure Loctite ® 425™ Assure™ Instant Adhesive, Surface Curing Blue Threadlocker is designed as a fast curing, low strength adhesive for locking metal and plastic fasteners. The product is designed for pre- or post-application. Loctite 425 cures quickly on plated metal and plastics fasteners; fixturing is achieved in less than 2 minutes and full strength within 24 hours. Fixture speed can be increased by application of a Loctite cyanoacrylate activator - e.g. 7113™. This product is typically used in applications with an operating range of -54 °C to +85 °C.
Might have some promise for pen work.
Loctite 425 Assure Threadlocker - Henkel
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