Bicycle Mechanics - Undoing red Loctite with heat gun?
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04-02-08, 11:57 AM
I have the original 27" wheels on my Schwinn World Sport FG conversion that would be ideal (and cheap!) for a Miyata frame I want to build up as a geared bike for my niece, now that I have a flip-flop rear and front hub + new rims to lace up for the fixed gear. I'm trying to keep the cost down. Otherwise I'd just buy hubs & rims.
I rotafixed the cog with red Loctite. I understand that it takes 500deg F to break the bond. Has anyone tried this with a heat gun rather than a torch? A heat gun would seem to be a bit safer and have less risk of overheating the cog or hub.
04-02-08, 12:36 PM
For 500 deg F, I would put it in my oven. This should give you the best assurance that you don't overheat it. You may lose some temper from hardened steel at 500 F though.
04-02-08, 12:39 PM
from what I've read, heat makes it easier but it can be broken without it by using enough force (back pressure, reverse rotafix, etc).
04-02-08, 07:58 PM
I have loosened bolts held with red loctite without using any heat. Heat does help, but not always necessary. If it seems to be taking too much effort, I will heat it. 200F should be plenty.
04-02-08, 08:00 PM
I'd try the heatgun. What can it hurt?
The only issue with a heat gun (and we run into this at work) is that you might actually heat up other things more than you want to due to how long it actually takes you to heat the piece. If it's a big enough sink, all you'll do is heat up everything.
I'd give it a go without heat first, little chance of damage there.
I agree. Try it without heat. I've used red on lots of motorcycle parts and RARELY had to resort to heat, though I sometimes used an impact driver as a persuader.
Go ahead and try without heat. But the red stuff is pretty stout, be careful not to apply more force than the aluminum threads can endure.
Heat is really not a problem. Even using a torch. Be methodical: heat a bit and try to loosen, and again and again until it breaks free.
04-03-08, 12:34 PM
Keep in mind that the heat melts the loctite. If you heat it and let it cool again it's still going to be tight. You need to undo it while it's hot from the oven or while it's hot from the heat gun. Stout leather work gloves would be a good idea.
A torch isn't so bad. The flame from a propane torch is quite large. Just keep it moving and don't let the inner cone of flame that is the hottest sit on any plastic parts. It should be hot enough to make water or spit sizzle and a little more. Much more than that and the plastic separators are going to start melting.
04-03-08, 12:47 PM
I believe the red locktite spec is more like 240 deg, not 500. Heat gun it and then try to get it off, add more heat if you feel like you're putting too much force on it. It should come off. That's the way you're suppposed to do it.
I never use red unless it is absolutely required by spec.
04-03-08, 03:41 PM
I wouldn't crank on it too hard. The locktite may actually take some of the aluminum threads off the hub if pushed too hard.
04-03-08, 04:52 PM
I use a tiny micro torch, about 4" away, moving in a circle around the loctite'd cog, and while holding the cog with a chain whip and applying pressure.
the cog will spun free with very little effort in less than a minute.
this is the way I loosen red loctite'd fasteners on motorcycles, except I use a box wrench, instead of a chain whip
My B&D heat gun goes up to 500°C (about 900°F), I guess it would temper martensite (hardened) steel and ruin bearing cups.
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