Cast Iron Housing Repair

[Bob_T]

I have some cracks and broken pieces from a nice old antique machine to repair. The breaks and cracks are on a machined part and if possible I want to avoid the necessity of deep veeing and welding since it will take me forever to resurface the part.

In a perfect world what I'd like to do is braze it with material that will sweat into the cracks and gaps by capillary action, similar to the way copper pipe fittings are sweat soldered.

I'm looking for a "high flow" (not sure if that's the right term) brazing rod or silver solder that will flow into the cracks without the necessity of major vee-ing. So far in talking to vendors they just tell me to use "regular" brazing rod, however, looking at some of the manufacturer's websites there must be 50 types of brazing rod alloys. Can anyone suggest a brazing or silver solder rod that will have good or better than average capillary action? Plus I'm assuming that the proper flux will have a lot to do with flow. In addition of course to operator skill.

These parts need to be fairly strong but if they fail it is not a safety issue.

Thank you for your comments and advice.

Bob

[Wyoming]

Depending upon the extent and application of your broken pieces, you might find a better solution foregoing welding and brazing altogether and use a good quality industrial epoxy. If you are looking for a high flow brazing rod, I would imagine that epoxy would provide just the action you are looking for. Some variants are machinable as well. Prep work prior to application would be similar to that for brazing minus the deep V-grooving.

http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=947828&PMAKA=505-2708

[Bob_T]

Wyoming, thanks for the suggestion of epoxy, I never thought of it. I have some Devcon around here but it's old and I'll get some new stuff and try it on two of the parts to see how it works. Not as much fun as brazing, but if it works it works.

[Hotfoot]

Epoxy is good stuff, but that particular type is a putty, which will not flow like to want. I've been using Locktite Epoxy lately...the industrial type that comes in two bottles (not tubes), and have been very satisfied with it performance so far. I think I bought it at Home Depot, about $16.00.

You do not mention if the cracks are under strain. My best cast iron Epoxy repairs have been where a piece just was broken off...from a bump or drop. My attempts to repair cast iron exhaust manifolds never worked. I use Plumber's Putty to 'back up' the crack to keep it from flowing out the bottom and sides. The piece should be warmed up to displace any moisture, and kept warm (not hot) for the first hour or so, Absolutely do not disturb for the first 24 hours...let it do its little 'ol epoxy thing!:)

[vicegrip]

3M has some good products, I need to find the exact name, however.

This kind of bonding has little tensill strenght, even the very best epoxy
can't match a weld.

What is broken and "why" ......... and further
how important is the original shape / locations.

Trust me, what ever broke it, and what are it's normal
stress's, will be all-important, to consider.

VG

[drizler]

I used Devcon to fix a freeze cracked head on my v6 Mercruiser with a Chevy 4.3 five years or so ago. No stress on it and it runs cold at 150 F but it held up great and is still there. I use it where JB Weld isn't going to be enough or if it will run off and I can't contain it in place. Still, for something that needs to support stress I wouldn't be that confident.