If you want to avoid the rust, it may be worth taking a leaf from the 'Precious Metal Clay' brigade.

When bronze clay is sintered in a furnace at around 800C the copper & tin components of Bronze PMC can oxidise to the point where the clay won't sinter. To avoid this, the components are put in stainless steel catering tins and covered with finely ground coconut charcoal (2mm granules). This is useful because the charcoal is not contaminated with anything that will promote carbon diffusion into iron, so the iron should not show any property changes. And the charcoal will prevent access of oxygen to the metal surface to cause the rust.

Just a thought.

Regards,

Richard.

Thanks Michael, If I do keep reporting on the build, I may move the information over to a dedicated thread which I can link here if I need to.

Wow that's a little lengthy, definitely the academic type wrote this! But pleasingly, it does appear to offer some documented scientific backing for the "casting skin" effect.

Although the only suggested method I can see for beating it is shot blasting, probably because It erodes away the non carburized layer.

He suggests that the cause is due to "metal to mould interaction". The difference in temperature, surface quality of the sand (and subsequent ingress of sand into a casting, possibly caused by the degree of roughness present on the mould surface). This might be the glossy layer I was referring to, it does seem to "trap" and encase the sand beneath it. I can't seem to find a notable mention of how annealing it helps, but it has definitely changed the surface quality of my own casting.

No doubt, some chemical or abrasive methods may work as well.

Michael W

Thanks Richard, I think that could come in handy when I want to anneal a casting that may not be necessarily be completely machined, thus preserving the surface from the cool down and reduce condensation. The coconut charcoal, may also be absorbing any build up of moisture from the casting, so that oxygen in the water does not get enough time to form a decent rust layer.

I was also thinking that I could wrap the castings in a kind of copper sheet housing, as the melting point is high above (1000ish) the range of my 900c furnace, and it has a good heat conductivity, the action of heating the copper as well as the iron could retard the cooling times as the furnace very gradually cools down, anyone think this could work?

It should be noted that the cavity size in the furnace is only around 9" square opening, so I can only fit small components inside (unfortunately!)

Michael W

Edited By Michael-w on 18/01/2017 16:08:33

Thanks Bazyle, perhaps one of my more "head on shoulders" decision rather than buying a fancy cutting tool!

The Clarke 4 jaw is notoriously overkill for the lathe, as it does not share the common PCD with the 3 jaw self centre, even they have to put a backplate on it! I have a 6" square block of steel I could probably mount on it.

Michael W

My tablet computer decided to terminate it's contract with me yesterday, so a trip to the local superstore was in order this morning to find a replacement. That in itself was the easy bit - recovering various files to transfer to the new device is probably easy for the younger generation but not so simple for a person like myself.

Fortunately this was offset by the arrival of a parcel from one of our regular advertisers (thanks Ketan) so now I have no excuses for not getting on with my latest workshop project. I'm also very impressed with the delivery service. They sent me notification of the intended delivery slot at about 8:30am, saying that I was no. 99 on the round and that the package would be delivered between 2:12pm and 2:42pm and also included a photo of the van driver! Needless to say it arrived right in the middle of the quoted times. Can't fault that can we?

Phil

Photoshop

Useful to know, I've had a bad experience of the 'bury in the ashes before you go to bed' approach. It softened the casting but it also made the flywheel look like a pretzel, presumably uneven heating.

Neil

Started reading this [on my 'bus journey]: **LINK**

https://archive.org/details/mechanicalphilo01carpgoog

.... Highly recommended, free download.

MichaelG.

Mechanical philosophy, horology, and astronomy

Not another! I have 1950 books from that site on a tablet. I have read just over 300 of them in the last 18 months, and am downloading at a much greater rate than I can read them. Got to stop...

Regards,

Richard

Neil posted, "Photoshop"

Oho! A challenge!

I call your bluff, what's false?

Geoff

Ah, thanks for the warning. I do actually have a flywheel that may go in there, i'll remember especially not to stand it on it's side, or I may end up with a special hot iron pressing ​

I guess I got off lightly this time as the wheel shape probably lends itself to that action all too easily even if it is laid flat. (supported on all sides might be the safest way to save me an unfortunate phone call back to stuart models).

Thanks for the tip

Michael W

Thanks again Michael, I've started reading it, but some (one or two) of the pages appear blank to me in my browser. I take it is so old they have been misplaced. It's very handy knowing someone who can gather such a vast array of material on a subject as wide as engineering and sciences.

Michael W

I popped into local agri engineer to see how my tractor is doing .. to find it's ready for collection. While there discovered that the young lad working there owns 'a few' traction engines. Also found out that we have a foundry about 20miles away in Llanrhaeadr-ym-Mochnant that apparently will do one-off castings. Could be handy.

Posted by Neil Wyatt on 18/01/2017 21:15:32:

Useful to know, I've had a bad experience of the 'bury in the ashes before you go to bed' approach. It softened the casting but it also made the flywheel look like a pretzel, presumably uneven heating.

Neil

​M-W

Have you done the cylinder & standard castings as well? my standard had a ring of chilled iron around the flange, managed to get through with a carbide tool... did think of getting the barby out to do the same but hadn't cut up some CI window weights to throw in as well at the time, just in case they had some chilled areas... maybe spring time... ​ , unless my next project - S50 - has some chilled areas... .



George.

The complete absence of random sheets of A4 in huge chaotic piles....

Haha!

You got me! Out of sight of the camera to the right. That's why I tidied up! Behind the camera is the electronics construction and test bench, then the radio station and opposite the camera, behind the computer, is the machinery section. No I'm not showing it! Because, 1) I haven't tidied that up yet, and 2) there are unfinished projects and forthcoming articles in preparation.

Geoff

My wife uses one of the 100mm deep 1/6 gastronorm pans, as seen in this e-bay sale **LINK**

Uses a lid too. Lasts 50-60 firings to 800C before the stainless turns to solid rust and gets so fragile you can hardly pick it up. This size just goes in the kiln.

Regards,

Richard.

After a week of on and off in the workshop finally finished the parts for fitting taper gibs to the saddle on my Sieg C3. Also added locking screws to the cross slide and compound. I used Rick Kruger's drawings as the basis for the gibs and retainers but had to adjust the dimensions to suit.

The difference is nothing short of astounding. I have now parted off through 50mm and 32mm diameters with a 3/32 x 1/2 parting off blade without breaking it or the saddle trying to climb over it.

Now whats next?

Howard

Excellent excuse, I'll keep it handy (there are several dozen such projects in the editorial workshop...)

Ah, well, "Keeping it handy" is what gives rise to teetering piles of A4 papers in the first place...

Geoff