Silver Soldering

[JssParticipant @jss]

Am I being over optimistic here?

This a big end bearing I’m trying to repair. I’ve bored it out and am hoping to put a leaded bronze liner in it prior to final boring and scraping in. I’m proposing to silver solder the parts together. I have the means to apply sufficient, uniform heat (oxy/fuel torch and motorised turntable). Having applied suitable flux to the surfaces and fed the solder in from one side, will the solder penetrate right across the 2ins to the other side? If not and I turn it over to feed from the other side will trapped flux prevent full penetration?

I have bought Silver-flow 55 solder which the seller said is suitable for most engineering metals (not aluminium), but read somewhere that leaded bronze requires a special solder so am not sure now. Does anyone out there have experience in soldering leaded bronze?

[Andrew CrowParticipant @andrewcrow91475]

I would have thought that silver soldering temperature might be a bit high for leaded bronze, maybe soft soldering would be sufficient for the use that the bearing will have have.

Andy

[duncan webster 1Participant @duncanwebster1]

Leaded bronze (SAE 660 probably) can be silver soldered, but not as easily as unleaded because the lead contaminates the flux. As Andrew says, I’d use soft solder or even epoxy. The joint doesn’t need much strength,  it’s only preventing the bearing turning

[Bill PhinnParticipant @billphinn90025]

Whether you decide to use silver solder or soft solder, you could sweat solder the concavities of the two halves first, pickle, smooth down any lumps, flux again, keep the three pieces of the assembly lightly pressed together, and heat until the solder visibly re-melts.

John Mills on his Doubleboost channel has done this successfully several times with soft solder on bigger pieces of bronze than you are dealing with.

[Andy StopfordParticipant @andystopford50521]

I asked CuPAlloys about this for a similar sized job – their reply was:

“There are problems with leaded materials as the lead melts first and comes to the surface.
We suggest 438/440 rods with HT5 flux and open up the joint gap a little to get more volume of brazing alloy in.
Hope that helps but if you need any further information please do not hesitate to contact us.”

In my case, since the use of leaded bronze wasn’t critical, I decided to avoid potential difficulties and used the non-leaded type.

[Nigel Graham 2Participant @nigelgraham2]

Given the the liner’s shape and material I would not solder it, but make a sort of tubular brass grub-screw that fits the oil-hole in the top of the outer part, the original hole enlarged and tapped to suit. The tip of the screw locates in an oil-hole in the new liner, and ends just shy of the bore.

The “grub-screw” thus acts as both angular retainer and oil-conduit through to the shaft.

Though I suggest using epoxy resin adhesive too, or bearing retainer, so the oil does penetrate the joint between the bronzes.

[paul raynerParticipant @paulrayner36054]

If its a case of just stopping it from rotating, why not just drill and pin/dowel it? Would save a lot of hassle including possible distortion

[Paul LousickParticipant @paullousick59116]

As already mentioned, use a pin/screw to stop rotation in the housing. This will also makes future replacement easy.

The bearings on my engine are made in 4 loose parts and the clearance with the crankshaft can be adjusted to compensate for wear. Clamp screws on each side and shims under the plate on top.

[Speedy Builder5Participant @speedybuilder5]

If you go the silver solder route:-

Advice from CuP Alloys:-

” Hint 3

Brazing Aluminium Bronze with up to 10% aluminium?

Add 20% by weight of table salt to the flux powder. The increase in chloride ions helps to remove the

aluminium oxide.”

 

[JssParticipant @jss]

Hmm looks like the consensus is to avoid silver solder. I’ll probably go with locating dowels and some sort of retaining compound. Thanks for the replies chaps.

John.

[bernard towersParticipant @bernardtowers37738]

What speedy says is correct, and what Kieth Hale doesn’t know about silver soldering is not worth knowing!

[duncan webster 1Participant @duncanwebster1]

Where did aluminium bronze come from, original query was about leaded bronze

[Bill PhinnParticipant @billphinn90025]

Just about to say the same thing. I was assuming we were dealing with LG2 or SAE660.

[duncan webster 1Participant @duncanwebster1]

Data sheet for SAE660 is here it says brazeable to some extent. It is allowed by Australian boiler code for silver soldered boilers, and I have silver soldered it.

Also according to Noggin End Colphos, which also contains lead, can be silver soldered.

I still wouldn’t do it in this case, easier solutions have been suggested

[Nigel BennettParticipant @nigelbennett69913]

Stupid question… Having silver soldered/soft soldered/epoxied it all together, is it possible with it in one piece to reassemble it on the shaft again?

I’ve not had any particular difficulty in silver-soldering leaded bronze; you certainly won’t melt it at the correct temperatures for Silverflo 55.

[JssParticipant @jss]

The idea is to fix the parts together, bore it out in the lathe, the split it and scrape to fit on the journal.

John.

[Nigel Graham 2Participant @nigelgraham2]

CORRECTION –

To my usggestyion above.

I omitted the word “not”…

…. so the oil does not penetrate between the bronzes.

 

Sorry about that.

(Second error this evening. I’ve just sent a plea for help to the TurboCAD Forum, after my fat fingers managed to give a very simple drawing a pronounced list to starboard.)

[Jss]

On Jss Said:

The idea is to fix the parts together, bore it out in the lathe, the split it and scrape to fit on the journal.

John.

The usual method is split it, stick it back together with superglue, bore it out, break the superglue. I’d just bore to size, but then I’m a crude so and so. You do need somewhere for the oil, too good a fit is not a good idea

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