White metal casting for restoration

[jfh]

In castings porosity is usually because of impurities.

If you cast without the centre piece all the impurities/porosity should be in the centre, but it's a very small casting so I think it's more difficult.
I would make the casting higher, ending in a funnel neck, this should ensure that the important part has defect free metal.
Just make sure to cast without a pause to prevent a cold shut, where metal didn't fuse because of cooling.

[mygoggie]

In castings porosity is usually because of impurities.

If you cast without the centre piece all the impurities/porosity should be in the centre, but it's a very small casting so I think it's more difficult.
I would make the casting higher, ending in a funnel neck, this should ensure that the important part has defect free metal.
Just make sure to cast without a pause to prevent a cold shut, where metal didn't fuse because of cooling.

Thanks guys for all the sensible suggestions. Brain and I will ponder on these and will try our hand at this again on Friday when I am back home.

[mygoggie]

It has been a week away from home to do some business. After all we need to eat and drink coffee!

I had a lot to think about especially with all the tips and ideas you guys offered. Thanks to everyone who contributed and made Brain's world ecstatically full of possibilities. I got tired simply thinking about how he was enjoying every avenue each tip offered.

This weekend I once again melted the previous attempt and tinned the casing once again. Each time I get more comfortable with this process and achieve a much better coated surface.








Next was to disassemble the SCCH and thoroughly clean each components. Amazing how much rust appears after only one week of laying around doing nothing ...






All cleaned and ready for action.






By now I have learned that the first step is to seal the hole in the casing. On goes a very thing layer of exhaust sealer.






Clamped and ready for heating.









Heating on low heat to allow the exhaust sealer to cure.







There we are!






The tinned surface is not oxidized from too much heat and it looks ready for another casting attempt.








Next step is to seal the back clamping piece. On goes a thin coat of exhaust sealer.






Clamped in place with sealer oozing out. This is good as I know that we have a good seal.







Plate cleaned with some water.







Next the holding plate gets some exhaust sealer.






Located with a casing and locked down.






The casing can be pulled from the two clamping plates with a bit of effort and this will allow the seating area to be coated in soot. Lamp black that is.







Inserting the sealed casing is a tad tricky.






You need to hammer it into place to ensure a very close seal and a total perpendicular fit to the channel section bottom.






In position and onto sealing the casing.






Sealer applied and heating everything with low heat to get the exhaust sealer to cure.







All done and ready for casting!








Or not ....

One thing I noticed and had a lot of time to think about is the fact that gas bubbles each time formed just below the top surface even when I stir the molten mixture. The metal also had a crystalline structure meaning it cooled very quickly and could not release the gas before the surface boundary formed and trapped the gas in the top portion of the casting.

So ... my next experiment was to add some mass to the casing to retain the heat in the molten metal a lot longer. I cut seven pieces of flat bar and strapped this to the outside of the casing.










Yeah yeah, I forgot to take a picture of the last side ... sorry ....



Next step was to lamp black the core piece or the mandrel as I learned is the correct term.








Yes, the other side as well ...






And installed ...






I wanted to add some ball bearings to the mandrel to give it some more mass to retain heat, but there was no way I could get this into position and still center the mandrel in the casing.






And then it was onto casting ...

I did not take too many pictures as I had a horrid time getting the molten metal to solidify correctly. It turned out that the added mass, allows the external side of the casing to cool much slower than the mandrel even with applying additional heat to the mandrel. It did however help a lot in getting much more gas out.

I failed in getting the molten metal adhering to the casing and shrinking away from the mandrel .... It shrunk away from the casing as the casing remained hotter than the mandrel and allowed the molten metal to shrink towards the mandrel.

It looks a lot better as a casting but is useless with no bondage.










So we learn. So we attempt yet another round of casting ...

[mygoggie]

Onto the now familiar melting of a failed casting ....

I gave the whole scenario a lot over my siesta time and decided (as suggested by @jfh) to make the casting itself higher.

By this time my camera's memory was full and I did not have the energy to clean myself up once again, move files from the camera and do another test casting.

I therefore went rogue and did all the prep steps once again, did not add the metal pieces to the outside of the casing and simply strapped a clamp to the top of the casing to make the casing taller or higher or longer or if you lie on your side and look at the casing, longer.

I did all the casting steps again. While keeping the mandrel heated to a higher temperature than the rest of the metal parts and the casing, I made another casting. This time a bit taller. Or longer or maybe wider??

While spraying water from below I decided to also cool the casing surface with compressed air while keeping the protection plate over the newly cast metal and heating the mandrel.

This is what I found after allowing everything to cool down. The crack formed between the mandrel and the white metal! Good!






Yes, and I cleaned my camera of pictures ...

So now I can take some more images!






Top clamp removed.








This time the gas bubbles were above the casing! The joint between the casing and the white metal also looks good!













Taking a hacksaw to the longer portion, I cut it flush with the casing and filed the surfaces level.








A few gas bubbles bit these will be machined away.







The joint between the casing and white metal on the topside looks solid as well!






At last! A usable bush!


Onto casting the second bush ....

[mygoggie]

This morning, I melted the second casing with the failed casting. It went well ...

I sanded the casing thoroughly, etched it with hydrochloric acid and then fluxed it. Tinning went well with a lot of flux remaining. I then remembered that you remove flux with ammonia and water.

Here I am scrubbing the tinned surface with a dish washing sponge and a mixture of ammonia and water.








Nice surface and very clean!









Onto cleaning and assembling the system again ... I can almost do it blindfolded now. Just need to learn to listen where the flame is burning as I keep burning myself when my eyes are closed.








When I woke up this morning, Brain whispered something like: "Find the gas source" in my ear. Makes sense. Why are there gas bubbles forming

I read a bit and learned nothing. I read some more and yet learned nothing. I read some more and then learned that only iron should be in contact with the molten white metal when stirring it. This made me think ....

I made the mandrel from stainless steel. Maybe some chemical reaction occurs between the stainless steel and the white metal? Let me make a new mandrel from normal steel piping and check if my theory holds no gas.

I scrounged around and found an off-cut in my last scrap bin in the greenhouse.






The pipe cleaned.






Marked the edges of the pipe where I will cut it. No, the lathe is still not running!






Making a mark with a pipe cutter which gives me an exact cutting line.






The mandrel ground with a taper to the topside. The above edge. The side we will push in. You get it don't you?







Cut to length and started sanding with 80 grit.






Polished to 250 grit and ready for action. If you call standing still in the center of a casing whilst bolted down action, then action is is!







Blackened for covert operations ...






All assembled with the clamp once again on top. I made a mistake earlier I only discovered at this stage. The bolt I used was bent ... too late now and I simply centered the mandrel and clamped it down. I was not going to disassemble everything and do the whole reassembling process again.

And ready to pour!







And poured ..






This time once again keeping the mandrel heated while cooling from below and blowing compressed air on the casing.

"Oh heck" .. OK, this are not the correct words I used ... as I poured the casing leaked.






At least the white metal pulled away from the mandrel and it was higher than the casing!






Removing the bolt was a futile exercise. It was stuck. What now??

Brute force worked to get the bolt loose. Loose from its bottom half that is. The reason??






The white metal leaked into the mandrel! Due to the bent bolt not tightening 100% onto the mandrel it obviously created a tiny gap at the bottom.






Oh well. I simply screwed the whole casing with the broken bit of bolt from the channel section.

Aha, the joint between the casing and the white metal looks good!






Propped up to cool down before I press the mandrel from the cast white metal.






This one is for you Brain!





Almost no gas holes!!










Well, well, so the stainless steel appears to have been the culprit!

I will leave this mystery to Brain to solve!

And then it was time to file the top surface level.








Almost done!






And filed level with the casing's edge






And the bottom end filed.





No cracking between the white metal and the casing at either end!








Yes, it does make a soft ringing sound. The casting is very thick with respect to it's length so it will not ring like a bell, but at least it does not go "thud" when you hit it!

And there we are. Two usable bushes.






The final proof of my efforts will be when these are machined to size. Let's see!

Thanks to everyone who gave ideas and tons of motivation. I really appreciate it.

Brain also appears to be very happy!

[SinWolf]

Congrats !!!!

[hbannink]

Welgedaan, enigste manier wat hierdie kon werk is eerstens baaaaaaie geduld en 'n groot hand vol vaardigheid, baaaie spiekeries geluk

[jfh]

Love your work.
Glad you have some good results.

[Peter Connan]

Great stuff!

Now I guess you need a lathe to machine the bores?

[mygoggie]

Great stuff!

Now I guess you need a lathe to machine the bores?

Motivation 101, yes!

[mygoggie]

Congrats !!!!

Welgedaan, enigste manier wat hierdie kon werk is eerstens baaaaaaie geduld en 'n groot hand vol vaardigheid, baaaie spiekeries geluk

Love your work.
Glad you have some good results.

Dankie manne, ja ek voel amper soos Job ... kort net die baard!

[mygoggie]

Uncle Brian helped me out this afternoon and machined the two bushes to an approximate close final size. This will allow the bushes to be pressed into place, aligned and bored to exact size.






Tonight I will make the side hole as this cannot be done once the bush is installed. The oil slots I can cut in-situ.

[plunger]

Does this need to be line bored. ?Why can it not be finish machined and pressed in ?

[mygoggie]

Does this need to be line bored. ?Why can it not be finish machined and pressed in ?

The required clearance is 0,05 mm and it must be aligned with the housing face which is aligned with the shaft.

[mygoggie]

Reamed and scraped ...

[ghouwens]

The required clearance is 0,05 mm and it must be aligned with the housing face which is aligned with the shaft.

This is most likely the reason why you cannot buy the bush loose. It is probably fitted to the casing and then machined.

[mygoggie]

This is most likely the reason why you cannot buy the bush loose. It is probably fitted to the casing and then machined.

Yep, Brain told me he figured this to be the reason.

[plunger]

This is most likely the reason why you cannot buy the bush loose. It is probably fitted to the casing and then machined.

Do you think it needs to be lined bored then. ?But 0.05mm is quite forgiving. Reaming can cause problems at times because its not accurate. If you bore a bush in a 3 jaw chuck and ream it to size chances are your hole wont be round. I'm still battling with this one and not being experienced enough I have had headaches. Reamers seem to follow holes so if your through hole is not true the reamer follows suit.

Best to clock up in a four jaw, bore and then ream. Some will even say use a floating reamer but thankfully my work doesn't demand such accuracy. Line boring obviously is true to how it would be in situ.

[EtienneB]

in our consumption driven society it is all too easy to stop trying after the first stuff-up and maar go and buy the part. But you kept trying and now you have a successful product. Highly highly commendable Sir!

[mygoggie]

Do you think it needs to be lined bored then. ?But 0.05mm is quite forgiving. Reaming can cause problems at times because its not accurate. If you bore a bush in a 3 jaw chuck and ream it to size chances are your hole wont be round. I'm still battling with this one and not being experienced enough I have had headaches. Reamers seem to follow holes so if your through hole is not true the reamer follows suit.

Best to clock up in a four jaw, bore and then ream. Some will even say use a floating reamer but thankfully my work doesn't demand such accuracy. Line boring obviously is true to how it would be in situ.

Clamp it on a CNC table and cut the installed bush to size. That is the way we decided.