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Welding Cast Iron

Repair of cast iron

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Speedy Builder501/07/2018 16:04:00
2502 forum posts
197 photos

The other day I dropped my rebate plane off the scaffolding whilst building a wooden garage. Of course, being of cast iron, something had to break and on recovery, the nose of the plane had snapped off. To repair it, I ground a 'V' along the crack line and welded it back on with Stainless filler wire using an Argon CO2 gas mix and the MIG welder. When it had cooled a little, I put a spot more weld on the back of the crack - a bit difficult to get to though !

plane welding46.jpg
plane welding50.jpg

I think I will leave the excess weld on the front until the day I need to get really close to the end of a blind rebate.

Jon Lawes01/07/2018 16:39:34
735 forum posts

Thats the difference between an engineer and the layman! Someone else would have just bought another....

Clive Foster01/07/2018 18:59:36
2993 forum posts
105 photos

Interesting that you used stainless MIG wire for such good results.

I've tried ordinary MIG filler with very poor results. Was told that the MIG heat is too concentrated so only a very small volume of the part being repaired gets really hot leading to very fast cool-down producing a hardened, brittle, joint line between substrate and filler.

Presumably the poor thermal conductivity of stainless slows the cooling process enough for the joint line not to go really hard.

Generally the stick welder buttering process where the joint is opened up to a relatively large Vee and filler initially built up from several thin layers made at lowest practical current before finishing with a normal size rod effectively welding filler to filler works well enough for me. But there are times when MIG wire in a smaller Vee would be a better fit.


fizzy01/07/2018 19:02:54
1836 forum posts
120 photos

Might it be cast steel and not iron, it welds OK?

Speedy Builder501/07/2018 19:20:39
2502 forum posts
197 photos

Interesting point Fizzy, it files like C.I. How would you tell C.I from C.S. ?

Clive Foster01/07/2018 20:55:46
2993 forum posts
105 photos

If it files like cast iron it could well be what our American friends call "semi-steel".

Basically a grey cast iron with a fair bit of steel added to the melt. Maybe 30 to 40% steel. SouthBend used around 40% steel in their mix. I've repaired a couple or three SouthBend components and it welds very nicely indeed. Lots of ordinary steels are worse. Best one was a broken gearbox end clamp eye on the banjo bracket off a Heavy 10 which went back together absolutely perfectly. Under a thou out of round with just the right amount of nip for adjustment when loose and needing minimal tightening on the bolt to make it stay.

As I understand it semi-steel in UK terminology refers to materials produced by specialised processing of ordinary cast iron, eg. nodular cast iron, rather than simply mixing in steel to the melt before pouring.


Speedy Builder501/07/2018 21:40:44
2502 forum posts
197 photos

It is an American plane ! I thought Cast Steel had bright flakes in it when you observe the broken face.

vintagengineer01/07/2018 21:58:40
468 forum posts
6 photos

Might be mallable iron.

peak401/07/2018 22:23:34
1597 forum posts
172 photos

A good friend of mine, a competent welder, but now sadly deceased, also used stainless on cast iron.

He normally used stainless to lay down/butter the first coat and finished off with plain steel; seemed to work well enough, even on car exhaust manifolds.


Nick Hulme03/07/2018 16:55:05
750 forum posts
37 photos

I use 316L wire and rods on Cast Iron, always with plenty of pre-heat and a well insulated slow cool, it works very well.

Brian Wood03/07/2018 18:46:22
2498 forum posts
39 photos

I only have oxy-acetylene gas welding and have had success with Sifbronze brazing rods and the matching flux to repair breaks in cast iron. Preheating and slow cooling is important


Speedy Builder529/11/2021 21:09:00
2502 forum posts
197 photos

Update, just been watching the YESTERDAY channel where they were repairing large decorative cast iron panels on a bridge in Edinburough. The panels were removed then the temperature of the panel raised overnight to 600 deg C before oxygen acetylene welding.


Martin Kyte29/11/2021 21:33:24
2638 forum posts
46 photos

If that is a Stanley No 78 then there are some interesting comments here.


Including the expectation of Brazed repairs exactly where yours broke.

regards Martin

Martin King 229/11/2021 22:56:57
940 forum posts
420 photos

Hi All,

I have seen and had no end of these broken No:78's, usually for spares.

I have never had any luck trying to weld them but now that I have my TIG unit I may have a go for fun. Not worth selling a repaired one though. I am just listing a nice complete boxed Woden version the last of three that I bought at a flea market. They used to do very well but not so good these days.

Lots of people sell them on EBay when cut down as "Chisel Planes" and the suckers seem to like them!


Martin King 229/11/2021 23:01:04
940 forum posts
420 photos

Martin Kyte,

Just noticed that your link is to Patrick Leach's Blood & Gore site; THE definitive Stanley plane resource on the net.

Patrick is a good friend and a great buyer and seller of rare and quality tools with a wealth of knowledge.

Cheers, Martin

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