Author Topic: Jason's " Rogue " casting thread.  (Read 5717 times)

Offline Alyn Foundry

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Jason's " Rogue " casting thread.
« on: March 01, 2016, 08:29:42 PM »
Hello All.

Ok, it's St David's day, so being welsh I'll open this thread.

Don't be shy..... Let's have a look at those castings.  ;)

Online Jasonb

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Re: Jason's " Rogue " casting thread.
« Reply #1 on: March 01, 2016, 08:38:32 PM »
Give us a chance I've just done a marathon post on the Jowit Cylinder ;)



I mentioned this thread a while ago and it has reared it head again. Its not meant to put people off using castings but may be useful for others to understand what may have caused a fault and how best to deal with it. I will not name the castings or maker to protect the guilty ;)

To start the ball rolling I'll use the same example that was in Jo's Triple thread.

Fault No 1 Voids

This bronze / gun metal casting looked qiute innocent from the outside, so into teh lathe it went to have the main flat surface machines and a couple of small holes started to appear, nothing critical.



I then had to mill a slot on the opposite side which revealed more holes than a bit of swiss cheese.



I don't think these were sand inclusions as they were within the casting and ther was no sand in teh holes (we will come to that case later)

Online Jasonb

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Re: Jason's " Rogue " casting thread.
« Reply #2 on: March 01, 2016, 08:49:49 PM »
Fault No 2 Porus castings (small voids)

An reasonable looking aluminium piston casting, even had a generous chucking spigot on the end.



Did not seem too bad as I started to machine the other end.



But as the OD started to get close to finished size low and behold a small hole or 3 hundread :(



Thats enough for tonight I'll see what other rouges I can find tomorrow :)

Offline Alyn Foundry

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Re: Jason's " Rogue " casting thread.
« Reply #3 on: March 01, 2016, 08:56:20 PM »
Sorry Jason, I was about to knock off too !!  :)

You're quite right that's not sand inclusion but looking at the very rough/ragged cavities I would say that insufficient " Head " on the sprue caused internal shrinkage, or a " cold shut/lock " during the pour.
This causes the casting, as it's cooling to feed itself rather than be fed from the runner. A simple remedy is to place a " Nob " ( cone shaped ) feeder near to the casting. This, because it's in the sand mould has a nice hot reservoir of metal to feed after the pour.

This is different to gas pockets, they are usually spherical and smooth to look at.

Kind regards, Graham.

I see our posts crossed, that's my explanation for your Gunmetal castings.

Offline Alyn Foundry

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Re: Jason's " Rogue " casting thread.
« Reply #4 on: March 02, 2016, 11:55:08 AM »
Good morning Jason and all.

Your piston casting is one of the worst I've ever seen, there has been no degassing of the molten metal before pouring.

Molten Aluminium loves Hydrogen it will absorb it from anywhere, it's mostly environmental, humidity damp tools etc. Leaving the pot to stew will take on lots.

Without degassing the Hydrogen starts to bubble out as the metal solidifies, your photo speaks volumes!!

A simple tablet containing Chlorine or Fluorine salts, " rabbled " through the melt will remove most and is best performed outdoors, the smell is both nasty and toxic. An " old hand " suggested mothballs but we used a proprietary brand of covering flux and degasser from a well known UK supplier.

A " backyard " foundry CAN produce a viable product if they use the right materials for the job.

Kind regards, Graham.

Offline 10KPete

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Re: Jason's " Rogue " casting thread.
« Reply #5 on: March 02, 2016, 11:59:03 AM »
Thank you for the excellent explanation, Graham! What about bronze/brass? Is there a similar cause/effect?

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline Stuart

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Re: Jason's " Rogue " casting thread.
« Reply #6 on: March 02, 2016, 12:19:30 PM »
Graham

Please correct me if I am Wrong but have I seen common salt wrapped in foil to degass with

In my dim distance past did they not use willow wands to stir the melt , not sure if that was brass though.

Salasilc acid ,aspirin come to mind

They used to vertically cast 36 inch CI pipes in pipe pits at the firm I used to work the core plug was well interesting, red sand, straw and horse dung  :insane:

Thanks for the information and yes I have seen lots of castings like Jason's and much worse

Stuart
My aim is for a accurate part with a good finish

Offline Alyn Foundry

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Re: Jason's " Rogue " casting thread.
« Reply #7 on: March 02, 2016, 12:31:30 PM »
Hello Pete.

Many thanks.

With Cuprous alloys the higher temperatures usually drive off any gasses but you still need to use a " covering " flux to reduce oxidisation and loss. Brass in particular, the Zinc burns brightly and will vanish without it. The amateur can use Borax but, as usual there's always a proprietary flux/refiner/degasser  available.

Kind regards, Graham.

Online Jo

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Re: Jason's " Rogue " casting thread.
« Reply #8 on: March 02, 2016, 12:51:23 PM »
As some of you know I consider castings to be a thing of desire: they are a promise of hours of enjoyment in my workshop that (hopefully) will result in a lovely model engine  :whoohoo:

However on my Triple thread I muttered about some flaws in the outside of my castings >:(. Graham identified it as being a result of loose sand falling back into the mould before pouring metal  :ShakeHead:

Jo
Usus est optimum magister

Online Jasonb

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Re: Jason's " Rogue " casting thread.
« Reply #9 on: March 02, 2016, 01:01:43 PM »
Thanks for the insight Graham, although at this stage there is not much we can do about some of these faults its good to know what causes them and how a good foundry will deal with them. Did you see my message?

Chilled or hard castings

These little surprises usually hid just under the surface of iron castings and tend to hide in corners or extremities. You usually don't know they are there until your HSS cutter suddenly goes blunt so always worth rubbing an old file over these hoding places or going straight in with carbide tooling.

Once you gave found the chilled matal it will show up as a shiny surface compared to the usual matt iron such as these.





With luck the casting will have enough machining allowance for the hard material to be removed but sometimes particularly if a hole needs to be drilled or tapped near the chill then you can get into problems as the HSS drill bit or tap won't cut it, this fuel tank filler is a good example, machined flat OK with carbide but the dark areas are still all hard.



Heat and a slow cool will often do the trick.



The annealed metal can then be worked.


fcheslop

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Re: Jason's " Rogue " casting thread.
« Reply #10 on: March 02, 2016, 01:02:43 PM »
Apart from the dubious machining
These Rider Ericsson  castings Im fighting with have a few problems

Iv never been a lover of castings wonder why :Lol:

Offline Alyn Foundry

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Re: Jason's " Rogue " casting thread.
« Reply #11 on: March 02, 2016, 01:28:53 PM »
Hello Stuart.

Yes common salt can be used Sodium Chloride, the Chlorine.

Willow was used to " Rabble " Brass in the early days. There were many recipes going round when the Midlands got into mass producing clock parts. Akin to alchemy!!

Ah, the foundry horse...... A vital part according to Roger the patternmaker. The manure made the best cores in his opinion. Then the urine also used diluted for non ferrous castings. He didn't miss the smell though!

This thread is bringing back some very fond memories, thank you all.

Kind regards, Graham.

Offline Alyn Foundry

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Re: Jason's " Rogue " casting thread.
« Reply #12 on: March 02, 2016, 01:41:25 PM »
Apart from the dubious machining
These Rider Ericsson  castings Im fighting with have a few problems
Iv never been a lover of castings wonder why :Lol:

Hello fcheslop.

Your photo shows two problems IMO, both covered. Little to no degassing and a poor running feed to the casting causing tears.

Had that been one of my kits you would have been given a replacement FOC.

Kind regards, Graham.
« Last Edit: March 02, 2016, 01:54:14 PM by Alyn Foundry »

Offline Alyn Foundry

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Re: Jason's " Rogue " casting thread.
« Reply #13 on: March 02, 2016, 02:05:03 PM »
Hello Jason.

Yes I got your message the answer is " fractional " . The number 6 that weighs half a Ton only developed 1/2 HP!

Chilled Iron castings are a nightmare your remedy is the only one IMO.

That Monitor casting looks really nice BTW. The pattern plays a key role in any casting. Roger told me you need to make them 110% otherwise the casting will never look nice.

I will write about finish and sand later.

Kind regards, Graham.

Offline Stuart

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Re: Jason's " Rogue " casting thread.
« Reply #14 on: March 02, 2016, 02:26:44 PM »
Graham

If you some more from the past  :
Note this is from when I was 16 now 69

My uncle was a brass mouldier that's where the willow wand info came from they used Coke fired hole in the ground crucible boy you had to be tough to pull them out

Another uncle used to do CI moulds built up with bricks covered in the afor mentioned material and struck off with a strickel /sp these were for large slag ladles and siphons used in the old town gas pipe work

So not done it but seen a lot done

Have you come across the old timers not wanting the sunlight to shine in the foundry because they judged the temp by colour , they would not tolerate the pyrometers

Now a bit for the steam buffs , the pipe pit crane was a king post crane hydraulic powered , fluid used cannel water the pumps were triple units ( not expansion jobs but three proper HP cylinder ones) with very large acumilators spread around the works

Boy that's made me feel old

Stuart
My aim is for a accurate part with a good finish