Silver soldering cast iron

[paul]

Current engine requires two cylinders created by blind bores in solid lumps of metal. As there's only about 2.5mm to play with at the outboard end and I don't posses the metal to make a 1/2" D-bit (!) I thought I'd bore straight through and fit cylinder covers but solder them on rather than bolt 'em as space is tight. Does cast iron silver solder ok or anything to watch out for?

Ta.

[circlip]

You don't half come up with some nuggets, first Yankee engines now gluing cast iron together You need a SPECIALIZED welder for this one Paul, recall some article advocating Silver Soldering cast iron for a piston Assembly - inner to a cup. In welding you need to heat unit up and use a high Nickel content rod. BTW you really should start looking for lumps of Alloy for your engines - 6082 - T6, if you look at Johns' bits on the other forum I think that's what it's likely to be. Regards Ian.

[AndrewP]

Could you bore it Paul? My smallest replaceable tip boring bar will go in a 10mm hole.
If you can get the cylinder in the lathe it wouldn't be too hard to grind up a hss bit to bore and bottom the hole.

Cheers, Andy

[jasonb]

Read an article in Model Engine Builder mag where the block for a 1/3rd scale Bently engine was Silver soldered from 3 lumps of CI, Guy used HT5 Flux and Cup alloys number 842 solder, got it to flow perfectly

www.cupalloys.co.uk/

Jason

[baggo]

Hi Paul,

'Soldering and Brazing' by A R Turpin says that most cast irons cannot be silvered soldered with the exception of Mehanite and Malleable irons which usually can be.

I am sure I've read in ME of people repairing broken cast iron wheels (e.g. chipped flanges) by either silver soldering or brazing.

It would be interesting to know what sort of iron was used by the Bentley builder.

John

[jasonb]

Just checked the article, it was machined from Spheroidal Graphite (SG) cast iron.

Jason

[albert]

Hello Paul,
I have come up with similar problems in the past .My way out first drill a suitable hole to near depth required and then either use a end mill to finish the bottom square or grind a suitable size twist drill to take out the last few thou,the hole acts as a drill guide and slow speed also helps.
Bye Albert.

[steam4ian]

G'day Paul

Years ago I brazed a cast iron tractor seat. Joints were a success but differential expansion from the heating caused breaks to appear elsewhere.
I suggest you would need to get the whole cylinder uniformly hot to stop cracking. That will probably stuff up your bore.

Could you make the cylinder cover fit inside the bore? Make it an interference fit and heat the cylinder to fit over the cover and shrink to fit when cold.

I can see myself doing that at the kitchen gas cooker, handy gas ring. ;D

Regards
Ian

[ianengr]

Hi Paul,

A friend of mine apparently treated the grey cast iron items with lime prior to soldering with the usual flux, but I would need to contact him again to get more details, would be happy to do so if you're still interested. Bronze welding was quite common and is not difficult in small sizes. I'm sure I have a picture of a full size steam loco cylinder being repaired that way somewhere, and automotive cylinder blocks were also done that way, both of those would obviously require serious heating throughout.

Kind Regards,

Ian.

[missemmajade]

it can be done with bazing. My dad spent a lot of his life brazing up large CI castings, and some smaller ones too. I was often helping. the weld prep. for SG iron is important, you need to either sandblast the joint or chip the surface with a chisel, a grinder will just burnish the Carbon into the surfuce, and as Carbon has a much higher melting point, the Brazing rod will never stick to it. its also important to get it hot enough, dad always says Blue heat is enough, just keep the colours swimming through the metal while its being welded. if its dirty and oily, a tiny amount of cast iron tinning flux may help, otherwise leave that alone, and just use powdered Brazing flux and a soft bronze rod. if its all hot and clean, then the fillet should flow in very niceley, just like melted chocolate. I dont see any problem in welding anything cast iron, the rule of thumb is that if you can melt a little corner, then it will weld fine. I've seen tractor and bulldozer fames welded, stamping presses, engine blocks, steam cylinders, radiator tanks, flywheels, all sorts. we had a place outside with a stack of bricks and cement sheet to build an oven around each casting, and an LP burner that would heat an engine block in about 20 mins! a fearsome thing to watch.

Not sure this is helpful to you, but it does need to be Very hot to hold. new SG iron shouldn't be a problem.

*EMMA*

[paul]

Whoa, that's a lot of suggestions!

circlip: Someone has to ask the daft questions!

AndrewP: I did that on the last one but the end of the bore was less than perfect. My Glanz tool will just go inside a 8mm hole. I tried making a thin HSS tool but it was way too bendy -->bin.

jasonb: Sounds like special materials are needed...

baggo: Ditto!

albert: I don't have a milling machine unfortunately

steam4ian: You crack me up. Tractor seats indeed!

ianengr: See below!

missemmajade: My cylinders are 1/2" bore ... I don't want to cook them!!

As this one may just be running on air (if at all!) I could bore straight through and just loctite some covers on the end. Bit of a cop out mind you...

Looking at it again I could fit one or maybe two screws, it'd just make it look a bit asymmetrical...

Thanks all for the advice...... thinking.
I'm waiting for jgb to

[circlip]

You must have a problem with your computer Paul, when I read my entry on my laptop, nowhere does it mention anything about your question being daft? It also states that I've read an article about silver soldering a cast iron piston together, If I could find the article I would post it but I'm a bit loath to do this as Tinternet seems to be re-writing posts? ;D ;D ;D ;D ;D ;D ;D ;D ;D
There should be 9 grins after that but I don't know what the software will have put out.
Just as a mod to this posting, I was sure I'd seen a horizontal borer on your bench?

[houstonceng]

My old dad (rest his soul) repaired a broken Record rabbit plane (made of CI) using a form of brazing - heat from Oxy-Acet kit.

Can't remember what the filler rod was or the flux (I suppose I could hunt around in the loft of the ancestral home - still owned by my sister - as the materials might still be there). IIRC, he asked BOC for advice and was told not to try welding it.

I'm still using the plane, so the job was a good'un.

I silversoldered a broken CI part Icap iron) on a cabinet maker's plane. Easy-flo and lots of flux. I think that's the point to make, the CI seems to exhaust the flux pretty quickly - so I gave to keep adding it in powder form

[ron]

I brazed a broken piece intothe main part of a cast iron Record plane many years ago at work, so long ago I've forgotten how but I'm still using the plane and I'm no whizz kid at brazing so it can't be all that difficult.
Ron

[Roger Mason]

Hi Paul,

You asked: Does cast iron silver solder ok or anything to watch out for?.

Dad (Len Mason) had always believed that it was not possible to silver solder cast iron, until he actually tried it. As a result of his experiments he devised a method of producing cast iron pistons for small petrol engines out of two pieces of cast iron silver soldered together. This procedure worked very well.

The cast iron used was from sticks of iron as sold by several of the usual suppliers. I suspect that this source of iron is somewhat different to the iron in a sand casting. Whether that would mean the silver soldering would behave differently I don't know.

I hope this helps.


Cheers,


Roger Mason, in St. Agnes.

[circlip]

Thanks Roger, hanging my head in shame that I didn't remember it was from one of the great L.C. articles, could have only been him or Edgar T. Regards Ian.