Casting practice

The clerk at MG Stevens told me the porosity meant my sand was too damp, though he gave me a small bag of broken degassing pellets.

I might take my patterns to a local art foundry:

So far I've built up machine parts that could be candidates for casting by welding, annealing and forging/jacking out the shrinkage distortions. Unlike casting all the metal doesn't have to be heated red-hot at the same time, and it gives the tensile strength of steel rather than aluminum.

-jsw

My understanding of hydrogen gassing in aluminum is that it's from the propane flame and dirty feed stock - and those degassing pellets are basically the same thing as pool chlorine IIRC . What you're talking about is probably surface porosity , which can be caused by excess moisture in the sand . Too hot a melt can contribute to that too . What I'm talking about is throughout the entire casting . After looking at where I've already machined this blank , all I've got this time is surface defects most likely caused by being too hot and the rough sand I used for my first batches of greensand . The rest of my crushed olivine and bentonite is coming home the day after Christmas . Then I'll have the materials to make finer-grained molding sand .

My sand came from the heap at an iron foundry. I used a plastic tub of Rutland stove gasket cement for the ingot mold pattern and some of the fine lettering from the bottom is legible.

That gasket cement works well to secure the cut end of silica braid on thermocouples to 2000F.

-jsw

I can help with casting:

First tie on what you will be casting. Then turn on all the brakes, and set the spool tension until so that from shoulder height it drops to the ground with only about one loose wrap as when it stops with no thumb pressure. Now practice at that setting with light side arm flicks. Once you have your hand trained for that you can let off some of the brakes or lighten the spool tension to cast better. Use your thumb to lightly feel the spool as it spins out while casting, and if it feels like its bunching up clamp down with your thumb to stop a bad cast. If you continue to have an issue with backlash stretch out as far as you think you will cast on average, and put a wrap of tape around the spool. Then reel up over the layer of tape. Practice until you can make good casts anywhere in that range 99% of the time.

LOL.

Fishing Arizona and the Colorado River

I'm glad you did it. I was going to suggest some tips for timing the backcast, and to stay away from shooting heads until he got that right with a double-taper, but I restrained myself.

Whats a good ratio of trout to pound of molten aluminum?

Does it matter if they are brown or rainbow?

David

"David R. Birch" fired this volley in news:m79oel011g1 @news7.newsguy.com:

I find roughly about ten or twelve pounds of brookies to a half-ounce of casting alloy -- just roughly. Usually, the metal is "lost" after too many re-castings, and must be replenished.

That ratio can be increased significantly with the right surface finish in the mold.

With the addition of sodium chloride, one can get the ratio up to a couple-hundred pounds of blues per ounce of casting alloy.

Lloyd

But brookies and rainbows are suckers for metal. Browns tend to be more demanding.

For them, the question is how many pounds of brownies do you get per wood duck? We won't lower ourselves to think about how many pounds of minnows it might take.

I'm doing the same thing using pool chlorine granules . My cup needs to be larger I think . How do you load your cup ? I wrap the stuff in foil and push it in . Plunge and stir and stay upwind of the fumes . I'm not real likely to go induction or resistance , I like the setup I'm using . Covering the crucible is an option , though that would make it difficult to add stock as it melts down . I think part of my problem is that this stuff came from stuff like truck rims and other dirty scrap . I also have some once-melted in an electric furnace stock that doesn't have the porosity problems .

I'm not a caster, but I've read that motor oil on dirty aluminum is a major source of porosity problems. That source recommended soaking your scrap in a warm lye solution to get rid of the oil.

But don't leave it in for long, because lye will also get rid of your aluminum. d8-)

short piece of black iron [no zinc] pipe. Hold in tongs or weld to rod. Use aluminium foil on each end. Fill with generic chlorine pool shock treatement. Plunge below surface and agitate, being careful not to breath the fumes.

In using "dirty"/salvage aluminium I have had some success in using a good amount of kosher salt as a flux. Dump in enough to form a skin when the charge melts and skim the large amount of dross that usually forms.

Perhaps it works because it etches off the oily layer of metal.

Dunno, just a guess...

I certtainly cleans it. But lye works on oil by saponifying it, which makes it soluble in water. That's how they make traditional soaps, by saponifying fatty oils with lye.

If you've ever had gun parts, especially barrels, professionaly hot-blued, the last step before dunking it in the bluing solution is to boil it in lye. Unlike aluminum, lye doesn't attack steel, but it saponifies any remaining traces of oil, which will wreck a hot-bluing job.

I've used borax in brass melts as a cover to help slow oxidation and zinc fuming , never considered it for a cover flux with aluminum . I've also used crushed glass with brass , what a mess that made . The set of rims these ingots came from were cheap wheels , spun/stamped/welded assemblies and they were pretty nasty , road grime and such. The ones I have left to process are cast and fairly clean . Maybe a combo of cover flux and chlorine degassing will clean this stuff up .

I saw the header and my mind immediately went to fishing. I thought you were about to reveal one of your secrets.

My fishing secret is that I don't ... I think the last time I wet a hook was probably 25 years ago .

I'm surprised that your li'l lesbian mind didn't think of knitting, Tawm. Y'know, cast on, cast off.