Casting defect how best to repair it?

[Lloyd W]

Good day to all,
Whilst machining one of the cylinder block aluminium castings for my 1/4 scale Merlin project I have discovered a small defect, perhaps a porosity that has generated a small hole ~1mm wide by ~2mm high at one end into the cooling water volume. Light shining through makes the white mark you can see to the right of the casting picture.

I guess Murphys law says you need to have done at least some of the machining to discover these things!!

Would any of you good people more knowldgeable than me have suggestions as to how best to remedy this issue?

Any comments/suggestions/remarks would be most appreciated.
Lloyd.

 

[GreenTwin]

I guess the $100 question is "Would JB weld hold up under those temperatures?".

I preach about being very careful about controlling metal velocity during mold fill, not letting the sprue aspirate air, and using a spin trap at the end of the runner.
I like bound sand too, since it eliminates sand inclusions.

I suppose some sort of TIGG operation could be used, but that could get very messy.
Obviously you want to use a safe method, whatever it is, so as not to risk damaging the casting.

.

 

[ChazzC]

JB Weld High Heat is rated to up to 500F

 

[The Ignoble Troll]

I do know a guy, well he's passed away now, who famously drilled two deep into the block of his wife's minivan. He accidentally put a tiny hole right into a cylinder.

He fixed it with just JB weld and it held up.


Alternatively you could try aluminum brazing rod, but that might distort the whole casting.

If it's minor enough, file under "extra character" and ignore it?

 

[byawor]

I would not suggest using solder. Many of those require a temp close to the melting point of the base metal so all of a sudden a small hole gets to be a big one specially if the casting is thin. A really good Tig welder might do it but again kind of risky. JB weld is your best bet. I think there are similar products for higher temp situations . Check McMaster Carr they have several different formulations.

 

[GreenTwin]

I don't think McMaster-Carr ships internationally.

.

 

[SmithDoor]

Good day to all,
Whilst machining one of the cylinder block aluminium castings for my 1/4 scale Merlin project I have discovered a small defect, perhaps a porosity that has generated a small hole ~1mm wide by ~2mm high at one end into the cooling water volume. Light shining through makes the white mark you can see to the right of the casting picture.

I guess Murphys law says you need to have done at least some of the machining to discover these things!!

Would any of you good people more knowldgeable than me have suggestions as to how best to remedy this issue?

Any comments/suggestions/remarks would be most appreciated.
Lloyd.

I have work on lot cast iron blocks and best was brazing.
This is a lot work.
Aluminum bocks are about same .
The cost goes very high

JB Weld is low cost option for hobby work. Must very clean and dry. Heating can also help drive the moisture before applying JB .
It typically where most epoxy fails. It was not dry and or clean

Remember jb is about 5,000psi and brazing is over 50,000psi strength

Good luck
Dave

 

[The Ignoble Troll]

I don't think McMaster-Carr ships internationally.

.

You just need to find a dealer that had a preexisting relationship with them before they went xenophobic

 

[ChazzC]

Amazon has both High Heat putty (450F continuous, 500F intermittent) and Extreme Heat paste (1,000F continuous), just search by name.

 

[Richard Hed]

Good day to all,
Whilst machining one of the cylinder block aluminium castings for my 1/4 scale Merlin project I have discovered a small defect, perhaps a porosity that has generated a small hole ~1mm wide by ~2mm high at one end into the cooling water volume. Light shining through makes the white mark you can see to the right of the casting picture.

I guess Murphys law says you need to have done at least some of the machining to discover these things!!

Would any of you good people more knowldgeable than me have suggestions as to how best to remedy this issue?

Any comments/suggestions/remarks would be most appreciated.
Lloyd.

If you could photograph this from a different angle, the angle where the hole is that you cut, it might give a better idea. You say this is the water jacket? It looks like a bolt hole but I cannot tell for sure. As long as it is NOT the cylinder, then JB weld is probably the best solution for cost and ease. But brazi;ng would be a better solution overall, me thimpfks

 

[creast]

I would machine it to a nice round hole and press fit a dowel ( could be aluminium too) with loctite 601 or similar and machine flush.

 

[Roger Taylor]

I would not suggest using solder. Many of those require a temp close to the melting point of the base metal so all of a sudden a small hole gets to be a big one specially if the casting is thin. A really good Tig welder might do it but again kind of risky. JB weld is your best bet. I think there are similar products for higher temp situations . Check McMaster Carr they have several different formulations.

The repair epoxy used for many years in machine work is Devcon. Check out their products, I know they have a steel infused epoxy, and they may also have an aluminum product.

 

[HMEL]

You just need to find a dealer that had a preexisting relationship with them before they went xenophobic

The reason many companies at least the smaller ones refuse to ship outside the U.S is due to the taxes and fees levied against American products that must be paid by the shipper and the additional time to keep the necessary records just to get it through customs. Nothing to do with xenophobia.

 

[The Ignoble Troll]

The reason many companies at least the smaller ones refuse to ship outside the U.S is due to the taxes and fees levied against American products that must be paid by the shipper and the additional time to keep the necessary records just to get it through customs. Nothing to do with xenophobia.

Just seems more fun to call it that, given they continued to deal with existing partners.

 

[peterl95124]

JB-Weld, Hysol 3455 and 9340, are all grey and high temp resistant.

you do not want to subject your casting to TIG or even braze temperatures,
you could have done that before machining, but it will warp and require
machining to get back to being straight/flat/etc and its too late for that now.

(and cosmetically you would probably not like the result either, what started
out as essentially a pin-hole would end up a big blob that would have to be
filed/grinded back to shape and still be an eye sore.)

this is a zero stress area, no problem what-so-ever with epoxy, and even with
boiling water that epoxy can't go anywhere so will be AOK.

 

[Billp66]

I would not suggest using solder. Many of those require a temp close to the melting point of the base metal so all of a sudden a small hole gets to be a big one specially if the casting is thin. A really good Tig welder might do it but again kind of risky. JB weld is your best bet. I think there are similar products for higher temp situations . Check McMaster Carr they have several different formulations.

I believe they make aluminum solider that melts around 400°F. I have never used any but have bought some. In this application a small torch would probably be needed. In other uses the claim of an 100Watt iron will work. YMMV.

 

[peterl95124]

I believe they make aluminum solider that melts around 400°F. I have never used any but have bought some. In this application a small torch would probably be needed. In other uses the claim of an 100Watt iron will work. YMMV.

you've never used it, so why are you advocating it ...?...

I did try some "aluminum solder" a while back, the flux turned the aluminum black and prohibited any wetting, it was totally unusable, yes I've seen youtube videos of people using it, but my experience says otherwise.

also even 400 degrees is going to be too hot for an already machined casting.

 

[GreenTwin]

Worst case, we may have to cast another one.
It can be done.
.

 

[hopperwhistle]

I have used a precision laser welding service in the past for similar repairs on very important castings. The results are so outstanding they have to be seen to be believed. They can do repairs so precise that with only one or two strokes of a file and you cant tell it was ever welded plus it would still be totally machinable after repaired unlike products like JB Weld. For larger casting flaws in places that dont need machined I recommend using high temp aluminum based filler.

 

[peterl95124]

Worst case, we may have to cast another one.
It can be done.
.

IIUC this is a Richard Maheu "Quarter Scale Merlin" casting,
only a few were ever made, he stopped making them long long ago,
they are very intricate lost-wax castings, he create the waxes and then
had a company in L.A. do the casting. they are irreplaceable ???