Silver soldering cast iron?

[AJWParticipant @ajw]

I am modifying a Suffolk centrifugal clutch assembly to drive an alternator which would ideally involve silver soldering my assembly to the cast iron clutch outer.

Never tried silver soldering of cast iron – is it likely?

Alan

[AJWParticipant @ajw]

[JasonBModerator @jasonb]

It can be done but not easy. You need to heat the CI first upto a high temp to drive the carbon to the surface and then wire brush it off before soldering.

Depending on your casting there may be a risk of fracture if it is not heated evenly.

Brazing may be a better option if you have the heating equipment.

[speelwerkParticipant @speelwerk]

The CI must be as clean as possible, I sandblasted it first the few times I have done it. Niko.

[AJWParticipant @ajw]

Thanks, I though it could be a problem as there appears to be so much carbon? I think in view of this pieces shape, quite a large 'cup' shaped casting I might be better off making a mechanical fixing to the alternator.

Alan

[HacksawParticipant @hacksaw]

Later , less well made Suffolks have a pressed steel clutch drum…interchangeable.. Might have one somewhere

[AJWParticipant @ajw]

Thanks Hacksaw! The cast one I have is quite a nicely made lump and should suit my purpose well.

Alan

[Keith HaleParticipant @keithhale68713]

Hi Alan

Yes it is perfectly feasible.

As Jason suggests, first heat the cast iron to red heat in air, (no flux) to burn off the carbon. Allow to cool naturally and clean with a stiff wire brush. Apply a long life flux, like HT5, and proceed normally.

I wouldn't recommend sand blating. If the sand gets into the surface of the cast iron, you would be in a worse place than when you started. You definitely cannot silver solder over sand!

Regards

Keith

[not done it yetParticipant @notdoneityet]

I’m with JB’s other option. If one can reach brazing temperature, it seems to be the better bet – braze is much, much cheaper than silver, for starters!

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