View Single Post
Old 01-22-2013, 05:14 PM   #59 (permalink)
HF Support
Posts: 29,516
Thread Starter Thread Starter
My HF Map location
Join Date: May 2006
Default Reposted from member Kiba

Loctite has 50+ threadlocker & retaining compound formulations-- not just blue and red. When it comes to threadlockers 242 (blue), 271 (red), and 290 (green) are the most easy to find versions because they are are double marketed both as industrial and "consumer" grades, the latter of which you can find on the shelf at almost any hardware or automotive store. Many more formulas of loctite are available from industrial suppliers.

Besides the specific version of thread locker used, the diameter, pitch, and length of the thread (i.e. total bonding surface area) has a lot to do with the final cured strength and torque resistance of the threadlocker. Using 271 high strength loctite on small 1.5-2mm bolts with only a few threads engaged will retain the screw better than 242 medium strength but the fact is there isn't much surface area for the loctite to bond to on the small screws so they're typically still removable without adding heat. Put 271 on a larger fastener (i.e. feathering spindle bolts) and the break away strength greatly increases and heat or a specialty solvent may be required for removal.

Loctite 271 (the commonly available high strength thread locker everyone calls "red loctite" ) is the high strength easy to find consumer version. 271 is recommended up to 1" diameter fasteners with no suggested limit on the small end so it is appropriate to use even on the small 1.5-2mm hardware found on our helis.

If you read the datasheets the standard medium strength "blue" 242 loctite that nearly everyone uses is recommended for 1/4-1/2" diameter fasteners-- a bit out of range for the hardware size on our helis and it's not the ideal product for the application.

Of the common "consumer" grades of loctite available 290 (green) is the most appropriate our helis as it is recommended for 2mm - 6.5mm hardware. It's a medium/high strength threadlocker and heat is recommended (but not required) for removal. My experience is that 290 develops a much more consistent bond on small hardware (4mm or less) than 242. It is a low viscosity "wicking" threadlocker that can be applied either pre or post assembly.

For a medium strength small-screw threadlocker the best product for the job is Loctite 220 which is a specific formula for small screws, it's recommended up to 1/4" / 6.5mm diameter fasteners with no limit on the small end. It is also a "wicking" grade and can be applied pre or post assembly.

Unfortunately 220 isn't a formula with "consumer level" marketing and you can't find it at your local hardware stores. However, you can pick up 220 from industrial suppliers (McMaster-Carr is always the easy source.)
Loctite 222 is the low-strength threadlocker for small-hardware applications but I can't think of an application on a heli where I would recommend a low-strength threadlocker.

Personally I use 271 on critical fasteners I can easily apply directed heat to (i.e. swash balls that can be easily heated with a soldering iron), 290 on critical hardware that I can't apply directed heat to and/or has plastic components nearby that limit the use of heat, and 220 on frame-related hardware, less critical hardware, and anything that may be removed more frequently for adjustment such as motor mount screws.
Slip fit non-threaded items (i.e. bearings) require a retaining compound that will vary based on the strength required and slip fit clearance. Ben covered all the appropriate grades to use for this application.
Helifreak, the place to be!
Oxy5 w/Brain2, Rush 750 w/VBAR,Logo 400SE, 600SE w/NEOs, TREX 450SE, 500, 600, Blade mCPX,130X, 180CFX, Nano QX, Convergence VTOL, MiniProtos w/BD3SX
My products, used by top pilots worldwide, like you!
rdlohr is online now        Reply With Quote