[How do I?] Repair Cast Iron

[foleda]

A friend bought a broken arbor press at an auction and I volunteered to attempt to repair it for him. Surfing the web a bit reveals several methods for joining cast iron: stick welding with Ni rods ($$$), brazing, and TIG welding with silicon bronze filler being the most common. I don't have TIG but do have stick, MIG and oxy-acetylene. I found silicon bronze MIG wire and am tempted to try that since I have the most experience with MIG but
I didn't find any reports of how well it works.

What recommendations, tips, & advice can those more experienced than I offer?

 

[Micke S]

That seems to be a real challenge since it need to take high loads. I think I would braze it to start with. Then true the whole bottom by milling. The next step would be to mount it on a real thick piece (e.g. 2+ inch) of steel or cast iron with screws from the bottom. I doubt it is possible to repair it without adding an extra stand unless you are a real expert on cast iron repair. I'm certainly not.

http://www.locknstitch.com/pdf/gmrc_white_paper.pdf

 

[Ulma Doctor]

if you have the OA set up and some bronze brazing rod,
i'd be tempted to braze it up after v-ing out the outermost crack lines near the surface to add a little more bronze material.
if possible pre heat the unit and stabilize the brazing area with clamps and stiffening helpers to keep your alignment and go to town.
if you can post heat it or put it in a pile of wood ash, charcoal ash, or sand it will cool slowly and resist stress fracturing.

if you have the NI rod, that's stuff's the bee's knees but i wouldn't go out and buy it, if i wasn't gettin' paid for the work.

if you have the mig wire that would be tempting too, you will most likely have penetration issues.
it may serve fine with a mig repair, i have welded very clean jaws to a CI vise with mild steel wire and 75/25 cranked up. not recommended but it can be done

after these considerations, your best bet may be the braze...

 

[coffmajt]

I would Braze as well. Use a rosebud torch to preheat as much as you can then add your filler -- Lots of flux and some time and you will be happy with the results -- Jack

 

[ch2co]

Ditto UlmaDr and Jack, although I do like the added base piece that Micke recommended, there is a whole lot of force trying to tear these things apart.

CHuck the grumpy old guy

 

[f350ca]

I'd arc weld it with nickel rod but brazing would work as well. Preheat is a must with either methods. When you groove out the crack avoid a grinding disk, they pack the surface with crud that affects the weld. I use a carbide burr in the die grinder, leaves the surface clean and ready to weld.

Greg

 

[rick9345]

Need good sized O/A, V-groove, preheat,Smith A-Mal-Gam style flux ,Brazing rod(1/4" for that thick), slow cool, BBQ(charcoal) grill works good pre/post heat. Ni-rod difficult to grind/machine to re-square that base.

 

[GarageGuy]

Wow, it would have had to fall off the work bench to break like that!

I would vee out the break with a carbide burr, preheat with your OA torch and rosebud tip, then arc weld with a NI rod. Keep heat on it afterward so it all cools down slowly and at the same rate. When I welded a cast iron gear, I used a quartz heater like the ones they use to cure powder coat. They will easily develop 450F+. Over a period of hours, I moved the heat further away so it cooled very slowly. On top of that, I like Micke S's idea of milling the base and bolting a steel plate to the bottom for strength. At that point you basically have a new arbor press that will last forever.

GG

 

[Rick Leslie]

I've always had good results with the brazing and preheat like mentioned above. If done correctly, the join is as strong s the parent material. Did this once on a 400 small block Chevy in the lifter valley/water jacket. Lasted until the motor needed another rebuild Preheat and clean joint/flux were the keys for me.

 

[Wobbles]

Any type welding is going to have misalignment, and she is not a beauty pageant winner. So you'll most likely end up having to fly cut the base to get both legs to share the load equally again.

I wonder if it might be simpler to epoxy the broken leg back in place, with ScotchWeld or similar industrial adhesive. This will give a perfect joint with no mis-alignment. Then after the cure, drill and tap for 2 large SHCS (above and below). The holes will be perfectly aligned since the parts will already be joined. Those will guard against shock loads.

You say the loads are high, but they will actually be "high divided by 2" since the other leg takes half the load.

Just an idea.