Need to fix an eff up, can I fill a hole in cast iron with silicon bronze?

[WobblyHand]

Managed to drill two bad holes into my lathe base. They are M6 and they just are in the wrong place. I am trying to mount my stepper motor on to my lathe. I don't have clear access to drill the holes which caused issues. One hole broke through the outer edge of the casting when tapped. The drilled hole was too close to the edge. The other is not straight and offset from the slot. (Lower than the slot and going downhill!) Both holes are on the bottom. The breakthrough is on the bottom left, and the total eff up is on the bottom right.

So can I use my TIG to fill the holes and start over again? Can I use silicon bronze? Or will I be generating more problems for myself? In any case, I will move the darn cabinet out of the way so I have a fighting chance to drill things straight. Really irks me to have messed up this last hole. I used the stepper mounting plate as a drill guide and still messed up the hole. Going to be hard bringing down the TIG welder into the basement, but I can't think of any other good way to plug the holes. If you can think of a better way to save this, let me know.

 

[Ulma Doctor]

I would not be afraid of repairing the mistake as you outlined. Silicon Bronze is often used to repair cast iron

 

[pontiac428]

You can probably tig the casting without warping it, it's a big heat sink. Unless you need to drill new holes that intersect the old ones, I'd just live with it. Maybe you could plug the bad holes with grub screws or flush-driven dowel pins. Measure twice when Murphy's watching.

 

[WobblyHand]

Unless you need to drill new holes that intersect the old ones, I'd just live with it.

That is the problem - the holes are almost in the right place - but not. I'm about 1/2 a hole off. I could alway make another slot midway on the bottom of the plate and put a hole there. Would clearly look like a screw up, though, and would remind me forever... Think I will attempt a repair.

 

[Lo-Fi]

Careful with the TIG on cast iron, it's not hard to get it to cook up the carbon and make an epic hard spot.
Also be careful to buy bronze rods specifically for TIG or you'll have a really bad day in the shop.
The alternative is to drill a bigger hole, thread, plug and re-drill if you have space. Call it an offset helicoil. If the cast is pretty clean and not lived it's life submerged in oil, you might get away with an epoxy putty repair similarly.

 

[WobblyHand]

I would not be afraid of repairing the mistake as you outlined. Silicon Bronze is often used to repair cast iron

My biggest issue is getting my water cooled TIG down into the basement, and then getting power to it. I don't even have a 220V outlet down there. I do have 220V in the garage and for the dryer (inside the house).

There is some room for a few more circuits in the main panel, but the electrician used up the neutral bar. (And the ground bar, but I extended it.) Have to extend a neutral bar to be able to even add any more circuits safely. Waiting for fall to do that. Old houses, the work never ends, and nothing is quite like you want it...

It's really weird that the number of holes in the ground and neutral bars is far less than the number of breakers that can be installed in the panel. It seems that they want you to double or triple up the connections on the bars.

 

[FOMOGO]

I think you would get a better result just brazing it up. If the holes have any depth to them it will be a little tough getting good penetration with the tig torch. Might be hard getting the drill to go staight with two different metals ,and might want to a least start the hole with an end mill. Mike

 

[WobblyHand]

Careful with the TIG on cast iron, it's not hard to get it to cook up the carbon and make an epic hard spot.
Also be careful to buy bronze rods specifically for TIG or you'll have a really bad day in the shop.
The alternative is to drill a bigger hole, thread, plug and re-drill if you have space. Call it an offset helicoil. If the cast is pretty clean and not lived it's life submerged in oil, you might get away with an epoxy putty repair similarly.

Not TIGging/welding the cast iron. Trying to use a silicon bronze rod which is a lower temp brazing process. I've used it before TIGGING and it wets steel pretty well, but doesn't melt the steel, however haven't done it on cast iron. I learned about it in a welding class. That was a year long night class at a trade school. Learned a lot in that class. Of course, that was 15 years ago, and I am sure I have forgot most of it.

Unfortunately one of the holes broke through the casting edge so there already is no place to drill larger! Kind of kicking myself on both of the bad holes, they never should have happened, but, I messed them up and now I own it.

 

[WobblyHand]

I think you would get a better result just brazing it up. If the holes have any depth to them it will be a little tough getting good penetration with the tig torch. Might be hard getting the drill to go staight with two different metals ,and might want to a least start the hole with an end mill. Mike

Holes are about 1/2" deep. I need just need about 1/4" near the surface to be solid enough to thread. I could pack the back with silicon bronze rod cut offs and melt it in place.

I do have oxy-acetylene as well as TIG. Do you think gas brazing would be better? I'm not all that comfortable doing oxy in the basement, as there's only one escape way out in case of fire. The tanks I have are pretty heavy for me to handle these days, I don't know how easy they would be to get into and out of the basement. SWMBO would probably not be amused if I broke any of the kitchen tiles, especially since we no longer have any spare tiles.

An end mill in a hand drill? Can you do that? Yes, getting a handheld drill bit to go true between two different metals is going to be hard to do. I was using 6mm SHCS, the holes were 5mm, so I need to get a 5mm end mill? How many flutes? I presume HSS? What could I use for a drill (end mill) guide?

 

[wachuko]

Why not make a bolt out of aluminum and plug it with that? Then drill again in the correct spot? It is not going to do a lot of force, right? Just holding that part in the photo?

Not sure why the need to plug weld anything…