Cast Iron Repair - Best Epoxy?

[Michael A. Tyree]

I too know how to weld, have the equipment and would not use epoxy. When I did work in industry I/we used epoxies that are not typically sold to street trade and perhaps that's a good fix, but I would braze it. It's a common, old time fix to braze cast iron, not something strange or expensive unlees nobody will do it for you reasonably in place. There are also stick weld rods made for cast iron welding. Every tech school I ever worked in used kept them around for repair jobs that came around. If it's not a high stress crack area, brazing is far cheaper than things mentioned above. Once you begin putting some epoxy on it the crack will never be as easily welded or brazed as it is right now. On a machine that vibrates it would avoid epoxy repair. All IMO of course.

[Tom M King]

Not yet. I'm still weighing the various options, & performance vs cost.

I should get to it sometime this week. I'll report back & with pics.

I hope it's somewhere that the surfaces won't oxidize.

[Monte Milanuk]

Hah! Never thought I'd see 'Belzona' mentioned on SMC

The hydro-electric dams where I work use that stuff by the tub for repairing cavitation damage on the turbine runner blades and the liner for the water passage. Work it in, smooth it out, let it cure and grind it smooth. When things get to the point where there is more Belzona than steel... air-arc torches to remove sections and then weld in replacement pieces. Big boy toys...

250px-Kaplan_turbine_bonneville.jpg

Baby version, but it shows the cavitation damage a little better...
1495287273-Cavitation_Propeller_Damage_opt.jpg

[Patrick Walsh]

He said it’s a big boy toy.

Now I gotta use just cuz

Really I do.

[Allan Speers]

I hope it's somewhere that the surfaces won't oxidize.

Actually, after degreasing, I plan on soaking them in a rust solution overnight (Rust911) then a quick detergent bath, and then immediately doing the repair afterwards. That should give me as clean a surface as possible.

[Allan Speers]

I too know how to weld, have the equipment and would not use epoxy. When I did work in industry I/we used epoxies that are not typically sold to street trade and perhaps that's a good fix, but I would braze it. It's a common, old time fix to braze cast iron, not something strange or expensive unlees nobody will do it for you reasonably in place. There are also stick weld rods made for cast iron welding. Every tech school I ever worked in used kept them around for repair jobs that came around. If it's not a high stress crack area, brazing is far cheaper than things mentioned above. Once you begin putting some epoxy on it the crack will never be as easily welded or brazed as it is right now. On a machine that vibrates it would avoid epoxy repair. All IMO of course.

All true, but brazing makes an UGLY repair. There's no getting around it.

Again, my particular piece doesn't get much mechanical stress at all, so I'm going for the cleanest repair, aesthetically.

I might also sink a couple of screws / bolts across the crack, as someone else mentioned earlier, but that's probably overkill for this particular repair.

[Jacob Reverb]

Whatever you do, my advice would be: Don't try to weld it. In my opinion, that's the worst possible (attempted) solution. And I weld a lot.

[Allan Speers]

FWIW, there's another method for repairing metal, though I'm not sure if it works on CI.

I saw this on Youtube, on "Jay Leno's Garage." There's a guy in CA that has repaired some super-rare, cracked engine blocks for Jay, using a new method called (IIRC) "stitching." From what I can see, it's might be sort of like tapping thread and installing reinforcing threaded rods, but actually it looks more high tech than that. The repair looks insanely good.

Jay mentioned that it was very expensive, so not the kind oif thing to use on a Taiwanese jointer! - But very interesting, regardless.

Do any of you guys know anything about this process?

[Allan Speers]

Heck, I found it easily. It's called "Lock-N-Stitch" :

https://www.youtube.com/watch?v=Pq0wfU4ZaKk


Definitely for cast iron. Not quite as pretty a repair, in this video, than I saw with Leno's blocks. I guess it's an artistic skill to some extent.

[Frank Pratt]

FWIW, there's another method for repairing metal, though I'm not sure if it works on CI.

I saw this on Youtube, on "Jay Leno's Garage." There a guy in CA that has repaired some super-rare, cracked engine blocks for Jay, using a new method called (IIRC) "stitching." From what I can see, it's might be sort of like tapping thread and installing reinforcing threaded rods, but actually it looks more high tech than that. The repair looks insanely good.

Jay mentioned that it was very expensive, so not the kind oif thing to use on a Taiwanese jointer! - But very interesting, regardless.

Do any of you guys know anything about this process?

I've never done it, just read about & watched videos of it being done. To my knowledge, stitching is done only for cracks where the part is still together. It is to keep the crack from propagating and to tie the edges of the crack together and stabilize them. I don't see how it could possibly join 2 pieces that are actually broken apart.

[Erik Loza]

Allan, whatever you end up doing, please make sure to post "after" pics. I think we're all invested now.

Erik

[Allan Speers]

I've never done it, just read about & watched videos of it being done. To my knowledge, stitching is done only for cracks where the part is still together. It is to keep the crack from propagating and to tie the edges of the crack together and stabilize them. I don't see how it could possibly join 2 pieces that are actually broken apart.

In one of the Leno videos, they had repaired and engine block that had a huge piston blow right through the block. So they MUST have replaced that blown-off piece.

Maybe the idea is to do some kind of braze or epoxy repair first, to align the parts, then do the stitching?

[andrew whicker]

How hot for silver brazing? Rule of thumb for me is to watch heat input on post machined surfaces...

[andrew whicker]

The only brazing I've done (forget the filler) was on structural steel and required red hot. Too hot to reliably keep dimensions if that's a big concern.

[Frank Pratt]

In one of the Leno videos, they had repaired and engine block that had a huge piston blow right through the block. So they MUST have replaced that blown-off piece.

Maybe the idea is to do some kind of braze or epoxy repair first, to align the parts, then do the stitching?

It must have been a piece that could be put back & was confined on all the edges. There needs to be something to keep the busted part from just falling away from the repair.