Von Willebrand

Happy Monday, everybody! This forum has been a wealth of information for a lurker like myself so far, so first of all - thank you!

Now onto the topic of my thread - I've begun overhauling a 1980s Trek that was handed down to me, but I've run into a problem with the rear derailleur. Specifically, the anchor bolt (as I believe it's called - please correct me if I'm wrong) is seized with the derailleur cable still stuck in it. It's a SunTour VX-S RD, and the part I'm referring to is circled in this picture.

The bike was in rough shape when I got it, so I assume this is likely due to rust/corrosion. I did a search and saw PB Blaster recommended multiple times for seized parts - I sprayed it liberally around the area and let it sit overnight, but it still didn't budge. I'm going to try PB Blaster again tonight, but I'm close to just throwing my hands up in the air and purchasing a replacement RD, as they don't seem so expensive.

Before I do that, does anybody have suggestions they can share?

Thanks in advance!

Slash5

Try holding a soldering iron on it till it's very hot. Let it cool and try removing again.
I've had good luck putting things like that in a baggie, put some penetrating oil in and then suck the air out. Orient it so that the bolt is submerged in the oil and leave it for a few days.
Ultimately you are going to need to put a socket on it and twist till it either loosens or breaks.

nashvillebill

Are you using a socket on the bolt head, or just a straight-bladed screwdriver? A socket can give you a lot more torque.

And I hate to ask....but you are indeed attempting to go counter-clockwise to loosen it? Just asking

In really desperate situations I've ground bolt heads off with a Dremel or side grinder, but then you're left with the shank of the bolt still stuck on place, and in this instance (small steel bolt in aluminum part) trying to drill out the remaining chunk of bolt would be extremely problematic, the drill bit will want to wander from the harder screw into the softer aluminum.

Another possibility to try, though: if you have a soldering gun or soldering iron, place the tip in the bolt head and patiently wait ten minutes or so to heat the bolt up. Then let it cool and try to loosen it. This may break up the galvanic corrosion between the steel threads and aluminum body.

eschlwc

i would submerge it in a coffee can filled with mineral spirits.

alternate between a wrench socket and a screwdriver.

3alarmer 

...those work better and are more durable than most replacements you can buy, so it's worth some work.

PB Blaster, while better than nothing, is not as good a penetrating oil as either Freeze-Off or ATF mixed with acetone. The ATF/ acetone thing is probably a non starter for you, because you have to buy a large amount of it. Freeze-Off ought to work well because of the dissimilar metals involved in your frozen part situation. In theory the cold shock of spraying it ought to contract the two metals at different rates, and produce some results. And as stated above, you really do need a properly sized socket or wrench on that bolt head to accomplish this.


If you have some convenient way to apply heat, you can alternate heat with the Freeze-Off (but it is flammable so be careful).

nashvillebill

Aw, go straight to Thermite....

TimmyT 

Cut the cable, remove the derailleur from the bike.
Submerge the derailleur in a solvent for a week.
Come back to it with a brass wire brush, and give the edges a little scrub.
Use a 6 pointed socket in a 1/4" drive ratchet, and it should come right out.