Seized bolts in Alu mast

[Heckler]

agree with you.
forumites tend to look so close at something that they end up looking up their a***s. then they try to outdo each other by using obtuse technical facts that in ordinary life have no bearing on the matter whatso ever.
bottom line when you have something corroded like that is tap it, bash it , oil it heat it and a combination of all the bits usually loosen it
stu

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[boatless]

Oh, I say...

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[Ships_Cat]

Assuming that it is a casting that the bolts are seized in you will likely find that it is cast from a very different alloy than motorcycle components, especially cylinder heads, etc exposed to high temperatures in service. The alloys used for those services are generally (but not always) of low corrosion resistance, whereas one would assume that a well made mast will use alloys of high corrosion resistance and it may also be that the casting is heat treated when finishing.

It may very well prove to be appropriate to heat a particular casting, but as I said before, there is no way I would do that on my own boat without seeking metallurgical advice first. It is very easy to suggest to others to do it on their boats as one does not have to suffer any unfortunate consequences, but I personally would not do that either.

If in the end the bolts cannot be removed by the soaking and other mild methods that others have sensibly mentioned, then I would be emotionally prepared to have to drill them out - real hard job but perhaps made less tedious if a cobalt alloy drill is used.

But there again, I am only a cat, so I obviously don't know what I am talking about.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Guest]

Totally agree ...

The asmount of heat needed would seriously damage the anodised and could affect the ally structure.

Suggest brute force and ignorance - then drill out the bits that break .....

Often striking the end of the bolts causes the ally oxide etc. which is gripping the bolt to realease its grip and allow removal.


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[misterg]

I wouldn't suggest anyone does anything they're not happy with.

The points I was trying to make were:

1) This is a potentially un-solvable problem

2) Give it a good soaking in diesel and try again.

3) Heat will help but may need to be extreme

4) Heating the BOLT can be done without similar heating of the aluminium, by virtue of the very corrosion which is causing the problem, but needs to be quick & intense. (Al melts before reaching red heat)

5) A mast foot is unlikely to be made of anything exotic, or be particularly highly stressed. If it meets these descriptions, it probably won't be harmed by the after-effects of 'shocking' the bolt. I wouldn't advocate heating the whole structure to these sort of temperatures - wrap the whole thing in wet towels while heating the bolt if needs be.

BTW - this treatment won't 'damage' the anodising, but it may discolour it if it has been dyed. I feel that corrosion resistance is irrelevant in this context - it's high strength alloys that need caution. (I would genuinely be interested if anyone knows for sure what alloys are used for this application, or m/c cylinder heads, crank-cases & engine mounts for that matter....)

6) Drilling a stainless bolt out of aluminium is DIFFICULT - you need to get dead center on the bolt, and drill it out in stages, dead square. As soon as you break out of the bolt, the drill will wander off into the aluminium, and start drilling a new hole. Worst case is that you can't keep the drill bit on what remains of the bolt, which is still stuck in the foot. Odds vastly improved by removing the part and getting it clamped in a drill press from the start.

If you don't fancy this, give it to the "yard". At least they'll have done it before, and if it all goes pear shaped, it's at least partly their problem.

(But I would rather live with my own bodges than someone else's /forums/images/icons/shocked.gif!!!)


Andy

(Ex metallurgist)

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