# Accidental hole in cast iron



## MrCrankyface (Mar 18, 2021)

Yesterday I did a mistake when working on a rear axle and the differential housing(cast iron) now has a hole in it around 1/2", of course on the bottom which would PREFERABLY be sealed tight and not leaking.   

I don't want to risk trying to weld this together, in fear of warping things.
Brazing could potentially be an option I guess but would require me to both get gas burners and rods.

I've heard JB weld might work, but will it attach strongly enough to the cast iron so the oil can't leak through?

Anyone have ideas how to fix my stupid mistake?


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## Braeden P (Mar 18, 2021)

duct tape!
How about something from flex seal that have a glue for everything


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## brino (Mar 18, 2021)

I believe as long as you clean the hole very well, and follow the JB-Weld directions (for mixing and set-up time) it would provide a long-term, leak free plug.

How thick is the area with the extra hole?

Another idea:
Could you tap it and use a tapered pipe plug? (Along with thread sealer)






-brino


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## Long Roof (Mar 18, 2021)

Can you tap the holw and put a plug in it, like a spare drain plug?


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## Shootymacshootface (Mar 18, 2021)

I have had excellent results with JB Weld on fuel tanks, both gas and diesel. Preparation is key.
A plug as above, would be my first choice if in a suitable position.


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## MrCrankyface (Mar 18, 2021)

I left the scene of the accident so to say quite quickly to avoid getting overly angry over my mistake..  
I had not considered a plug, I will see if that's possible.
Otherwise I will clean the inside and outside as thoroughly as possible, add some physical indentations for the JB weld to grip and try to make a plug out of it.

Will return with pictures of my adventures.


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## RJSakowski (Mar 18, 2021)

What is the nature of the hole?   If due to something punching though, there will be a strong tendency of the fracture to grow.  When repairing cracks in cast iron, it is common practice to locate the ends of the crack and drill and plug to prevent the crack from spreading.  

If the hole is because of drilling, it can be plugged.  I would tap it to the next larger size  and thread in a JB Weld coated plug.  If the casting wall is too thin for threads, a patch could be made by forming a "rivet" with two washers, one threaded on the inside and  a second outside, and a screw with liberal application of JB Weld to hold it all together.  

This would be much stronger than just patching with JB Weld alone,


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## nnam (Mar 18, 2021)

If other options don't work,  cut around the perimeter to clean up and prevent cracks, then  put a piece of  thick sheet metal, hammer to shape, rivets and Rtv will seal it well.


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## Weldingrod1 (Mar 18, 2021)

I would screw a plug in if at all possible. Use.loctite or JB weld on the threads. You can dress it flush and/or coat it with JB weld afterwards if you want to pretty it up.

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## Nutfarmer (Mar 18, 2021)

I wouldn't try to braze or weld it because the critical tolerances of setting up the bearing pre loads and the ring and pinion. The heat will warp it enough to cause problems. If it's in a critical use I would replace the housing. If not what have you to loose by trying some of the suggestions above.


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## graham-xrf (Mar 18, 2021)

brino said:


> I believe as long as you clean the hole very well, and follow the JB-Weld directions (for mixing and set-up time) it would provide a long-term, leak free plug.
> 
> How thick is the area with the extra hole?
> 
> ...


The "close it with a tapped seal" idea is great, but be careful of over-tightening if using anything tapered. Use some white PTFE plumbing thread sealer tape, and screw in gently, until enough that it will stay.

If the region around the hole can be regular enough, then a non-tapered sealing cap plug with a nitrile O-ring seal, or one of those Dowty types with the sealing ring incorporated into the underside of the cap screw head. These are very common pneumatic/hydraulic parts.

I say this because tightening a bolt into a hole in cast iron puts the iron into tension. Cast iron is strong in compression, but utterly feeble in tension.

By coincidence, I happen to be putting J-B Weld to the test (another thread). It does seem strong, and it does hang onto cast iron, and it can be reinforced with carbon fibre or class fibre strands if you want. I am using "MarineWeld" which is claimed to be "Chemical & Petroleum Resistant", and has strength 5020 PSI. This I take to be the tensile force/area at the point it fails. This stuff is the fastest, least stressful, and lowest cost fix. I would try this before any of the others.

The point made by @Nutfarmer is well made, but the thing is broken. You can try any or all of the suggestions, knowing in the end you need to find a replacement. It depends on how rare and precious is the housing. You can't just go fetch another part from the store for a '68 Caddy DeVille!

I am shortly to attempt welding on cast iron myself, though I seek to first have a "practice run" on some old disc brake castings. After consideration, the method will be to slowly heat up the whole part to about 300C, and use E-NiFe-C (55% nickel) rod, made for welding even dissimilar metals to cast iron. This mix apparently alleviates some of the stress shock from cooling with different temperature coefficients, and exploits nickel ability to "wet" adhere to cast iron.

In my case, the casting metal is 50% semi-steel. You can bet that a differential housing will also be of tough semi-steel. No way can it be plain grey cast iron as might be used for a railing ornament. It has to take a pounding from the suspension!

The method will be to heat the whole thing up to about 300C, then lay in welds a little at a time, with pauses to allow the local heat to even out, and not allowing it to cool. When enough weld is on, then lay it in a box of wood ash, or vermiculite (is that kitty litter?), and let cool slowly as possible. Then grind/file back to where I want it to be.

Direct experience from the farmer who lives out back of my place is that when he attempted a cast iron weld with nickel (pure), the weld went on, but cracked immediately it cooled. Undaunted, he just ground out the crack, and tried again. Second time around, attaching to the existing weld, he said it was totally different experience, altogether successful. I dare say casting distortion was not a concern to him!


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## Aukai (Mar 18, 2021)

My dually rear end housing rusted through in a spot at the center section, JB weld did hold. I wire brushed, and ground down everything on the outside, I also used numerous cans of Brakleen to positively get all of the oil out of the area.


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## MrCrankyface (Mar 18, 2021)

I was using an angle grinder with a cutoff disc to remove a extrusion on the differential housing which used to hold a bolt.
I figured the casting would be thick there to support the extrusion but as this thread proves, it wasn't.
I used a flashlight to check how it looks inside and it won't be possible to drill and thread since it opens up at an angle as the lines show.

The shape should provide a really good grip for the JB weld though, so it can't get pushed out.
I will try toget the area a bit more flat and see if I can screw a plate into the cast iron and then JB weld over that as well to make it a bit prettier..


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## Mitch Alsup (Mar 18, 2021)

{Humor mode = on}
You could change the cam in the engine so it runs backwards, flip the sprag in the starter motor and wire + to - and vice versa, and flip the differential upside down.

Alternately, you could build a time machine and go back to yesterday and tell yourself not to be so ......
{Humor mode = off}

Personally, I would silver braze it--mainly because I already have the tools.


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## Chewy (Mar 18, 2021)

Looks like the stuff that used to be brought to me.  I spent years fixing farm and logging equipment, so I saw a lot of "mistakes". You cleaned up the outside so here is what I would do.  1. Try to find anything threaded that you can force turn into the hole. Pipe plug, bolt, electrical box connectors, just look around. If you can get it started and it is solid, coat the threads with JB weld and install.  You only need 1/8" of threads inside, if that much. Minimum on the outside. In other words don't leave an inch sticking up. Use excess JB around outside and all over.  It will hold forever.  The rear axle is vented, so all you want is to seal the oil in and water out.   Goes without saying that you need to make sure you have some clearance inside housing and that the JB area is clean, clean, clean. 
2. Use a freeze plug or something similar to jam into hole. Do the same with JB weld.
3. Take off the back cover and put plate on inside and outside, install with machine screw like 10-32 through them.  I put the head of the bolt on the outside and nut on inside, just me.  Clean inside housing and plates. Use JB as gasket instead of RTV on both plates.  JB the nut in place and JB all over on the outside. 
4. Do the plate thing on outside.  That involves drilling and tapping. Again use JB for sealing between housing and all over outside. 
5. Welding is absolutely the last thing I would do. Brazing or silver solder first.  Bear in mind that you will ruin the rear cover gasket when you do any of this.  I would stay with cold repairs all the way. I have done nickel welding on cast iron blocks and things and it is the last choice always. If you do one of these, I would still JB over the outside.

If this is your first time, it is scary and your trying to figure out how much it will cost you. After a while it is an easy repair.  Several years ago I rebuilt a 5L F150 Ford.  Made 1/2 mile down the road and lost oil pressure.  The Intake manifold freeze plug popped out.  The correct plugs just didn't seem right to me. I switched to a disc type freeze plug.  Put it as deep in the hole as I dared and then filled the hole and over it with JB. With 75K on the engine, it held 60 Lbs pressure at startup today.

3 years ago I had to JB an aluminum A/C suction line.  That is done just slightly different with masking tape.  It was still holding charge last fall.

My 2 cents.  Good Luck!!


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## tq60 (Mar 18, 2021)

It can be soldered but that requires a bit of heat and skills.

I would make a cover that fits over the hole with good overlap.

Next a length of material that goes across the hole on the backside.

Drill and tap 2 holes, spaced such the screws rest in the ends of your hole.

Transfer punch holes to cover and drill for screws.

Use long thread bolt to hold inside part to cover and hook in the inside.

Align and place other bolt and make sure it clamps down tight.

Once satisfied it will properly cover clean all mating surfaces and make sure cover is sanded to allow grip.

Coat both surfaces with RTV or epoxy and assemble into hole.

Once in remove one screw at a time and add thread lock and tighten up.

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## Shootymacshootface (Mar 18, 2021)

Where abouts is the breather on that? There needs to be a vent somewhere.


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## eugene13 (Mar 18, 2021)

Most rear end housings I've dealt with are cast steel, clean it real good and weld it.


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## LuJon (Mar 18, 2021)

eugene13 said:


> Most rear end housings I've dealt with are cast steel, clean it real good and weld it.


I was thinking the same thing. Use the cut off scrap piece to test welding. If that isn't going to work. Then make a cover out of 3/16 plate and tap 4 holes in the housing to bolt it to. Flatten the area around the hole with a big bastard file so it has something to seal too. 

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## Chewy (Mar 19, 2021)

If you decide to weld, solder or braze, the hole, you need to cover up the gears inside.  The last thing you want is spatter and little drops of steel on the gears or loose inside

You could tack weld the plate on the outside and cover with JB.  If it is cast steel, it will weld real good.  If cast iron expect cracks  and maybe the welds coming apart. Depends on skill and preheating. Personally for $5 of JB, and 10-15 minutes of work, I wouldn't take a chance.


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## Richard King 2 (Mar 19, 2021)

If you use the JB Weld think about your Dentist filling a tooth.  Grind the bottom of the hole wider so it will anchor in.  I have also had good like with https://www.cleanersupply.com/Press...re-Parts/perfect-putty-2-part-epoxy/?sku=PUT1


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## Chewy (Mar 19, 2021)

Richard has a valid point.  Do that wherever you can. Also, leave grinding lines on surface to give a good bite into metal. And you can always use aluminum fly screen for stiffening. Think mini rebars for concrete. Over 10 years of fixing old equipment, I have done at one time or another, everything suggested above.  Your hole is in a non pressure housing, up top, and only subjected to "sling" oil on the inside and water on the outside.  JB or equivilent epoxies will work fine, but do try to get a mechanical bite on the housing and make sure there is a little lip or something to keep the "plug" from ever falling inside.


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## MrCrankyface (Mar 19, 2021)

Well this was an absolute adventure!  
Milled out some brackets that fit snuggly around the axle tubes, roughly aligned everything and started flycutting a flat.



Next up very slowly drilling with a 19mm bit.
Very interrupted cut since the hole is oval.
Drilled roughly 25mm/1" deep so even tho the threads aren't great, there'll be a fair few to take the load.




Tapped it with BSP 1/2"(Just what I had on hand in the right-ish size the hole.)
Testfitting with a generic plumbing bracket and seems to have worked out alright!




Hopefully you find this view as amusing as I did.
The table would seize up with the axle loading the table so far to the left, so I had to add this hefty square tube on the right to even things out, it's almost 12.5 / 1/2" wall thickness so weighs about the same as the axle.



The idea is to either make a custom plug or buy a brass one, then seal it all up proper with JB weld.
This way the JB weld doesn't need bridge the entire hole.


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## eugene13 (Mar 19, 2021)

Is it going in a hot rod or a racecar?


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## Aukai (Mar 19, 2021)

I was looking at the bracket, but thought not with that pinion flange I'm thinking.


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## MrCrankyface (Mar 20, 2021)

Not sure if i'd classify as a hot rod or race car but it started it's life as a Volvo 13134.
It looks decent but trust me, looks can be deceiving.
Lots of hidden rot..





This is just a small sample of what i've replaced so far when it comes to sheet metal work..







I'm currently reconstructing it with a completely different engine and rear axle. The 'new' rear axle being wider I've also reshaped the rear fenders.
Not to mention that I'm going from 14" rims with 165mm wide tyres to 18" and 245mm wide tyres.
Currently working on a new 3 link suspension for the rear axle(which is what started this whole problem with the axle hole) and a new subframe since the old was rotted through.
The car will have a full rollcage, air suspension and almost 4 times the horsepower that it had stock but will be meant for the street.
Highly unlikely that I will take it racing.


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## Shootymacshootface (Mar 20, 2021)

MrCrankyface said:


> Not sure if i'd classify as a hot rod or race car but it started it's life as a Volvo 13134.
> It looks decent but trust me, looks can be deceiving.
> Lots of hidden rot..
> View attachment 359817
> ...


Awesome project! I love the unusual.  When I saw the picture, I had to make sure that you weren't from the states!


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## MrCrankyface (Mar 20, 2021)

Thanks!
What made you think it was from the states? Made me curious!

I was close to driving away and buying a plug but started questioning why I have all these tools if not to use them. 
Quite decent fit and will probably seal up on it's own with some gasket material but rather be safe than sorry and will apply JB from the inside at a later stage once I have the differential taken apart.


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## FOMOGO (Mar 20, 2021)

Great repair, but inquiring minds want to know exactly how you poked a hole through that casting, and will that dif hold up to all the new power? Cheers, Mike


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## MrCrankyface (Mar 20, 2021)

Thanks!
This is an older picture before I butchered the axle(Note that the custom lowerlink mounts has been on and off the axle several times as I've been trying to make things fit).
As I was removing old brackets that won't be used on this car, I decided shave off the brackets in red as well.
I thought they'd have plenty of material beneath them, but well, they didn't.



The axle is from the same kind of car as the motor(Volvo 940 turbo)so it should stand up for the increased horsepower.
Unless you're running supergrippy tyres they can usually manage 300-400 horsepower and I'm aiming for around 250-300.


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## mattthemuppet2 (Mar 20, 2021)

was the upper bracket a mounting point for a Panhard rod? Cool fix, though I'd be tempted to just slap some RTV sealant on the plug and leave it as a removeable (fill or drain, depending on top or bottom) plug for the diff. Make it a feature 

Have you posted up elsewhere a thread on your conversion project? I love reading about those, they're super interesting and you learn alot of different ways of fixing problems. I help out a friend who buys and partially restores (basically what you're doing but no further) old American classics then sells them to buy another one. Always something interesting going on in his garage.


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## MrCrankyface (Mar 21, 2021)

Both brackets that were circled are for some kind of torque arm(not my photo).
The panhard sits on the protrusion on the left on my photo, behind the axle tube,



Maybe I'll try with just a gasket at first, if it leaks it should be obvious fairly quick, being on the bottom and all...   
I'm posting about it on two swedish forums and was considering putting up a thread about it on here but wasn't sure if anyone would be interested!


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## brino (Mar 21, 2021)

MrCrankyface said:


> I'm posting about it on two swedish forums and was considering putting up a thread about it on here but wasn't sure if anyone would be interested!



Very interested here!
-brino


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## mattthemuppet2 (Mar 21, 2021)

very cool and very interested! Just go see Alloy's "not a mustang" thread for an example. There are lots of gearheads on here, including some (not me) that do it professionally.


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## MrCrankyface (Mar 21, 2021)

Well, for anyone who wants to read about old cars in horrid shape, I've made a thread here:








						Volvo Amazon 1965 (Volvo 13134)
					

Alright so I've been on and off about wether I should make a thread about this, but it does have a fair few machining related projects. As usual with my threads, there'll be a lot of photos.  I bought this car back in march 2019, the motor wouldn't run and the car itself was in pretty poor...




					www.hobby-machinist.com


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## Just for fun (Mar 21, 2021)

MrCrankyface said:


> Thanks!
> What made you think it was from the states? Made me curious!
> 
> I was close to driving away and buying a plug but started questioning why I have all these tools if not to use them.
> ...


Cool project for sure.   The plug looks like it would make a nice drain plug.   I would install a copper gasket and call it good.   Maybe even drill out the end of the plug and glue in a magnet.

Tim


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## mattthemuppet2 (Mar 21, 2021)

good ideas Tim!


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## eugene13 (Mar 21, 2021)

Good fix, it looks a lot like you're doing what I'm doing.


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