Removing ss pins from aluminium casting

dgadee

dgadee

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I am moving lines back to the cockpit and need to remove the clutch arms and replace the old bearings. Both are held in by pressed in pins. I seem to remember that there is a means of using acid to remove the corrosion between ss and aluminium. I intend to do that before I press out the pins. What is the acid? Is it the stuff you put down a toilet?

boomend.jpg
 
A simple and harmless way to try is to get a can of freezing mixture and try a few squirts ....goes down to minus 50 C. Although in this case the metals are the wrong way round as the aluminium will shrink more than the steel pins the procedure has a generally disrupting effect which might just break up corrosion products.
 
reeac said:
A simple and harmless way to try is to get a can of freezing mixture and try a few squirts ....goes down to minus 50 C. Although in this case the metals are the wrong way round as the aluminium will shrink more than the steel pins the procedure has a generally disrupting effect which might just break up corrosion products.
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That's an idea I've never heard of before. I'll give it a try when I get round to trying to remove the 52 year-old s/s screws securing my halyard winches to the aluminium mast.
 
reeac said:
A simple and harmless way to try is to get a can of freezing mixture and try a few squirts ....goes down to minus 50 C. Although in this case the metals are the wrong way round as the aluminium will shrink more than the steel pins the procedure has a generally disrupting effect which might just break up corrosion products.
Click to expand...
I tried that on an aluminium fitting with some stainless pins and it didn't work. Ended up getting a machine shop to sort it out. When I asked how he did it he said tricks of the trade ....
 
Put them in a pan of boiling water and simmer for an hour or so. After that you will probably be able to tap the pins out provided you use a slim punch and are careful not to spead the ends you are tapping.
 
I seem to remember Vyv Cox being the proponent of acid. Can't find his post on the matter.
 
dgadee said:
I seem to remember Vyv Cox being the proponent of acid. Can't find his post on the matter.
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Ah, found it;

"Yes, I suggested that HCl might be a far better chemical method than Coca Cola or other methods often suggested. The corrosion product is probably an insoluble carbonate that is readily dissolved in HCl. I have posted a pic several times showing an aluminium masthead antenna bracket with the stainless antenna base firmly stuck inside it. A few drops of acid released it in a couple of minutes."
 
I'd guess those pins are not just corroded in place but peened over to retain them from new?
If so, removing them will probably involve drilling the stainless to remove the mushroomed end.
 
Wing Mark said:
I'd guess those pins are not just corroded in place but peened over to retain them from new?
If so, removing them will probably involve drilling the stainless to remove the mushroomed end.
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May be but that is not obvious. One end has been given ridges so it looks as though it was pushed in at the other end and held by being slightly enlarged at that ridged end.

You might be able to see what I mean in the image if you enlarge it.
 
dgadee said:
May be but that is not obvious. One end has been given ridges so it looks as though it was pushed in at the other end and held by being slightly enlarged at that ridged end.
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Are both ends the same diameter? If so and no other pins etc securing then they may well be only held in by the press fit. Either way the corrosion won't be making much difference to the difficulty of removal. You might get lucky with a hammer and drift but a hydraulic press may be needed; holding it square for either is the hard bit and may need a wooden fixture making.
 
If you can't get access to a press, as suggested by Penfold, you could try a large vice with a piece of round bar of slightly smaller diameter than the pins against one jaw and a length of steel or brass tube on the other side to receive the pin; or simply a block of wood with a hole in it.

Once the knurled end is clear of the casting it should then be very easy to push the whole pin out.

Lubricate the screw of the vice so you get maximum force.
 
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dgadee said:
May be but that is not obvious. One end has been given ridges so it looks as though it was pushed in at the other end and held by being slightly enlarged at that ridged end.

You might be able to see what I mean in the image if you enlarge it.
Click to expand...
It might have a serrated surface on the stainless pin pressed into the casting.
You could try supporting the casting and punching the pin out.

As pictured, it looks perhaps like the pin was pressed in from below, while the top side was supported.
You cannot probably support the top part of the casting while pressing the pin down IYSWIM?

I would suggest that the pin is easy to replace with a length of rod, bolt or WHY, but the casting is not.
Therefor I would be happy to sacrifice the pin in order to save the other parts, or to avoid risking trashing them.
Better to remove 'meat' from the part of the pin which is pressed into the stainless, so it can be pressed or knocked out with less force, than to damage the castings.

I might try moderate heat and mild use of a hammer and punch before getting the drills out.
But this time tomorrow you will perhaps think needing a new pin is a much better situation than needing a new casting.
 
Poignard said:
Yes, and a soak with penetrating oil before starting on it won't do amy harm.

Looks as if someone has already had a bash at it with a centre punch:


View attachment 125869
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Me! Didn't want to crack the casting so left it when it was obvious pins would not easily move.

And, yes, knurled is the term. Just out of bed after a few days illness so brain/words not working together.

I have access to a press (though vice could be used to cobble a solution). But casting not thick, so keen to get rid of possible corrosion before I press them out.
 
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