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THE AM BULLETIN BOARD => Technical Forum => Topic started by: aa5wg on February 26, 2012, 04:43:15 PM



Title: Loctite thread locker
Post by: aa5wg on February 26, 2012, 04:43:15 PM
Hi to all:

I would like to use some Loctite Thread Locker (Blue or Red type) inside an antenna coupler.  The thread locker would be used on 316 stainless screws that thread into brass taps.

Has anyone tried this product in a high power HF/RF environment (160 meters - 6 meters)?  This legal limit high power antenna coupler is for AM and RTTY duty cycle.

I was wondering if the thread locker would melt or get soft?

73,
Chuck



Title: Re: Loctite thread locker
Post by: Pete, WA2CWA on February 26, 2012, 08:39:50 PM
Blue: It protects threads from rust and corrosion and prevents loosening from shock and vibration.

Red: It protects threads from rust and corrosion and prevents loosening from shock and vibration. It is only removable once cured by heating up parts to 500°F (260°C).

Why would you want to use either one of them? You're using stainless steel screws so rust shouldn't be an issue. You also plan to subject the tuner to lots of shock or vibration?


Title: Re: Loctite thread locker
Post by: k4kyv on February 26, 2012, 08:48:11 PM
I think there is also a green one.  Maybe it's the same stuff as the blue.

I sometimes use it on screws and nuts that would be difficult to access and unlikely to need removing.  Collins uses it on the set-screws in some of the 75A-4 dial and tuning mechanism.

Sometimes heating and cooling cycles can cause hardware to work loose. Some of the hardware in my transmitter works loose.  Transformer vibrations maybe?  But I don't normally use Loctite unless for some reason I don't want the screw ever to loosen under any circumstances.



Title: Re: Loctite thread locker
Post by: Pete, WA2CWA on February 26, 2012, 09:03:29 PM
Nail polish works too; hobby stain paint; even Duco cement. Under average use, holds screws in place and easy to unscrew the hardware.


Title: Re: Loctite thread locker
Post by: K7EDL on February 26, 2012, 09:46:52 PM
I have used Locktite on firearms, the blue stuff is less strong than the red.   The way you break locktite loose is to heat it with a torch or soldering iron to expand part and break it free. I don't know how hot these parts are going to get but it is a consideration.
If in doubt I would check the locktite website or email the company
Eric


Title: Re: Loctite thread locker
Post by: WA1LGQ on February 26, 2012, 09:55:20 PM
The blue loctite #242 makes a stronger and more heat resistant bond than the red #222 especially with brass in my experience. Make sure the pieces are free of grease or oil. If you use 242 be careful if you have to remove the screws, make sure that you have a good mechanical bond between the  screw head and the tool to get good torque. Stainless steel screws can be a lot softer and easier to damage than a hardened steel bolt. A hex or socket head screw is a good choice. Don't use the green stuff unless you really want to have a hard time removing the screws or it is intended to be permanent. Use enough heat and it should break free though!

......Larry


Title: Re: Loctite thread locker
Post by: K5WLF on February 26, 2012, 10:25:46 PM
Spec sheets for all Loctite products are available on the company website http://www.loctite.com/ (http://www.loctite.com/), including temp ratings.


Title: Re: Loctite thread locker
Post by: aa5wg on February 26, 2012, 11:09:43 PM
Everyone, thank you for the input.

I was considering the blue loctite.  

I am using two small hex head screws to hold two pieces of brass together.  Each brass piece has a milled radius to match half the copper tubing radius. 

If a screw should becomes loose it would be a slight pain to get at to tighten.  Thus, I thought the blue thread locker would be good insurance.  However, I do not know if this stuff can take the RF without melting?

Chuck


Title: Re: Loctite thread locker
Post by: K5WLF on February 26, 2012, 11:14:05 PM
Everyone, thank you for the input.

I was considering the blue loctite. 

I am using two small hex head screws hold two pieces of brass together.  Each brass piece has a milled 1/2 radius to match the copper tubing. 

If a screw should becomes loose it would be a slight pain to get at to tighten.  Thus, I thought the blue thread locker would be good insurance.  However, I do not know if this stuff can take the RF without melting?

Chuck

Chuck,

I scanned the 242 spec sheet today and there was no mention of RF. Only of the working temperature range. I'd guess, and it's just a guess, that unless you're getting inductive heating up to 300°F, you should be fine with 242.

ldb
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