Frozen bolt in girder fork top yolk

[Richard Kal]

Help;
My 1927 Model A has a frozen link arm bolt, in the upper (handlebar) casting.

So far nothing has been able to shift it; heat, heat plus rattle gun, reasonable force, unreasonable force, or even bad language.

The bolt itself is in good condition (threaded end and hex head end), so I would like to be able to re-use it.

The thread is RH. Is there any thread in the handlebar bracket (casting)?

Would it help to soak it in a mild acid (ie phosphoric)?

Woulsd anyone have a casting, and bolt?

many thanks,
Richard
Western Australia

[adrie.degraaff]

Heat untill red hot.

[nevhunter]

You can remove rust by leaving it in a bath of molasses, or passing a small DC current through a caustic solution for a day or two. Get the polarity right and a stainless steel object is OK for the Anode? Hose it off and the rust turns to a black substance that washes off easily with water. Being in a tight space it may take a while to get through. Grease doesn't help the caustic to penetrate so heat may help dry it all out first. Nev

[john.whiting]

The most effective penetrant for rusted in parts is dilute nitric acid[ 30%].This solution has a very low surface tension,and it dissolves rust very quickly.Make a little dam of plasticene around the joint,and drip some in .It will go clean thru in a few minutes.I have used it to loosen very large assys in a marine situation.Needless to say,wear proper protective gear,or preferably take it to someone who can do it for you.Dont soak overnight or you ll have nothing left.Regards John.

[Tadas.Buchas]

I've been suggested to heat a bolt I want to undo and pour brake fluid on it while it's hot.
Haven't tried that though.

Some say Coca Cola works too. Eats up your teeth, eats up your rust.

I'm lucky to escape with just WD-40... For now.

Cheers,
Tadas.

[brenton.roy]

Hi Richard,
For really stuck bolts, I heat, oil, heat etc., because I think the heat "cracks" the rusty joint, allowing some thin oil to make its way in.
I think penetrene is the best stuff for this. https://www.blackwoods.com.au/search/pe ... /307019539.
I've seen this product from Loctite before, but haven't used it. http://www.loctitefreezeandrelease.com/ It would have to work in the reverse way to a gas torch.
Also, cast iron melts and cracks. Be careful with an oxy.

The caustic method Nev describes is in the knowledgebase, but might work better externally as it seems to remove the oxygen from the rust, rather than dissolving it (as Nev says).
I'm stumped about the chemistry. Sodium is more reactive than iron, so the black stuff isn't an iron hydroxide. There doesn't seem to be any change to the hydroxide solution - re-useable...
Apparently this method is used to preserve museum pieces - http://nautarch.tamu.edu/CRL/conservati ... htm#Sodium
Any proper chemists among us?
Brenton

[robin.parker]

I have often been disappointed with WD40 as a release oil, but find "PlusGas" to be really very good. The 30% Nitric Acid idea sounds well worth a try, I'll get me some of that!

[Richard Kal]

Eureka!

Heated the yolk to dull red, then pressed the go button on the rattle gun.

After a minute or so, there was movement at the station, and the bolt moved slightly.

I let it cool, then soaked in WD40, and after more use of the rattle gun, the bolt was out.

Thank you everyone, for your helpful advice!

Finally, there is a slight amount of wear at either end of the bolt.

What was the original made of; mild steel? Silver steel?

Would stainless be OK?

Richard

[Knud.Degnbol]

Never use silver steel for forkspindles.
It's brittle.

[nevhunter]

Silver steel is dangerous It is Carrotty. Something a bit better than mild steel is OK, bvut if you wanted to be fussy you could carburise a bit of nickel content steel and harden it and grind the spindles. Nev
Rust is a hydrated oxide of iron. It has water incorporated in it. ( Brown coloured) If you heat it, it forces the water out of the molecule and it goes almost black.
I don't know what the reaction is with the caustic but the rust is like fine soot that rubs or washes off.
With a tight fitting part the difficulty is getting ANYTHING to go in there. A big lesson with this one is the rattle gun. action. ie intermittent. When you are trying to loosen something try to move it each way and once you get the tiniest bit of movement just keep adding thin oil and it will gradually free itself, as you continue to work it back and forwards ... Nev