Information on metallurgy, casting and foundry work

[Pipescs]

I will throw in here that I just ordered another hundred pounds of Petrobond from a place on line called

Petrobondforsale.com Located at:

http://shop.petrobondforsale.com


105 pounds was 149.00 with shipping. I had originally bought 100 pounds from Budget casting for around 170.00 but they no longer carry it.

I was finding that the one hundred pounds I had was enough for only two midsized or one large mold which limited how much I could do in a day. The one time I worked with Fender using two hundred pounds we made five small molds as I remember.

[Grantham]

Hi Charlie

If you're near any shop that does marine work, some ships use zinc as a sacrificial anode which are replaced before they are completely eaten away. Another source may be a plumbing repair. Water heaters sometimes have zinc sacrificial anodes which prolong the life of the water heater. These should be free. If you don't mind paying, Budget Casting Supply has ZA27 for $3.85 a pound, which includes postage.
http://budgetcastingsupply.com/Metals.php .
My experience is with ZA12. It machines beautifully.

Also junk car dealers may be worth looking into. Parts of carburetors are zinc as older cars with door handles were zinc. We have a metal buyer/seller that actually sorts their scrap. If you're any where near Grand Forks, North Dakota, the place is Residual Materials. If my memory serves, they want 80 cents a pound for zinc. Nice folk to deal with.

Rod

[Grantham]

And Charlie, this may be too little too late, but . . . My favorite supplier for foundry stuff is McEnglevan. Their petrobond is $54 for 50 pounds plus shipping,
http://mifco.com/MS/catalog.php?op=inventory&cat=10
so we're in the same price range. Something to consider.

Rod

[steamin10]

As this thread flows out, the undercurrent of cost comes out , that this hobby is by no means free. Zinc stock for example, has be found to be of such and such, and must be sawed into usable small blocks to add to working melts. Well so be it. I adjust on my feet, and only use scrap for most furnace stock, with a few of the mentioned cheats. teh exception is Everdure, that will ruin you in cost and good castings from Virgin bar.

Please note that my first wooden flasks, were no more than 2x4 material, with hardware store strap hinges, and a lock hasp for a closure. The traditional wood flasks in cherry and so on, were just too expensive to justify, and would only make sense in a commercial setting where they are used and abused every day.

As far as waxes I have purchased some quantity of Brown 'continental' wax, and machinable, and glue waxes and all that, and a bunch of picks and hand tools for cleaning up a wax pattern. I have not poured in waxes, but will do so as other details dmeand attention now. I plan to use plaster of paris with a mixture of white bag sand, about 50-50 for the first pours. This worked well for some art work I did in aluminum. I am going to experiment with some dry molded vacuum sand, also.

There is an oil sand that is home brew that will cut the cost of your sand bill, as you noticed 100lbs is not a lot to work with, and is expensive. What will you do when you burn out the sand and it begins to fail in molding? Knowing what makes it work, will allow you to add some of the chems and get back to good sticky molding sand.

It is in one of C. W. Ammens books, and I will repeat the formulae here, as it was developed by a University, and is not complicated by copy problems. This formula is not mysterious, and should not be. I have to find the right book. The Archives might have it also, as it has been posted before.

I have had little success with the wax master/casting process, due to setting fire to the kitchen oven with melted wax during a test. The stuff burns like diesel fuel, so more special equipment is in store before I commit to a lot of waxes. I am using a vinyl molding product that reacts when heated , and goes from a liquid, to a solid when cooled. It is the same stuff more or less for those squirchy fish worm, and online sex toys, just a little firmer. This stuff is poured around a part and then split with a scalpul, or razor to remove the pattern, and create the pocket for the wax to be poured. I use a dipper that is a tomato sauce can, to fill the molds, and while I cant do all of it yeat, a cookie shooter provides the wax round beads and other shapes, extruded onto a 1/2 inch glass plate with some wax paper on it. When the wax cools to body temperature, it becomes pliable and can be worked into just about any shape. It is fascinating, if you have tried to be Artsy with wax. If you can carve it, you can make just about anything . I use plaster of paris for the investment, and havenot complained about the cost or the fact you have to bake it dry or face metal explosions.

I currently have my furnaces broken down and connot persue any casting at the moment, as time is getting the better of me.

[Grantham]

Hi Big Dave

To make lost wax casting less exciting, we steam dewax. This also removes the stink and the mess in your burnout oven. You might enjoy my video on Centrifugal and Vacuum Assist Casting,
https://www.youtube.com/watch?v=MvOKy3Msa4I , which shows the many steps involved in the process.

To insure good results, proper waxes improve results. You may notice a red wax in the video, which is sprue wax. Sprue wax melts at a slightly lower temperature than the blue plast-o-wax of the model. This melts before the model, decreasing any internal pressure in the mold. On larger casting the pressure of the melting wax can damage the delicate details captured by the investment. Other waxes like water soluble wax, sticky wax, etc., all serve a purpose and result in better castings.

We prefer vulcanized rubber molds for wax injection although for some items, like fragile jewelry or duplicating other waxes, RTV rubber works well. I don't have any experience with sex toys and I've been married for 44 years. Oh well<g>.

It's been said that investment casting is called that because of the substantial investment required (and we're not talking about the gypsum, silica, cristobalite materials in the investment powder).


And Dave, I am also accused of being long winded.

Rod

[Pipescs]

Bottom line is always start with you pigged revert, no more than 25%, and preferably about 15% if you can match up your pours that well. The trick here is to get a consistant feed stock, be it brass compression fittings , plumbing brass, or other homogenous source, to eliminate the SWAG movements on making your home brew alloys. If you buy 50lb of sink faucets, except for the trashy plating, what is the difference from the ingots they poured these from? Consider it once pigged.

Sample Problem to see if I am getting this:

I being a model locomotive builder have not been to concerned with my metal content except for the Trailing Truck Parts I am making. For these, I have used Silicon Bronze ingots wanting the strength.

I normally start out with an amount of scrap I buy down at the local scrap dealer. Then I add old bad parts or pigs from previous melts In the past it has not been measured by weight but I now understand I should go somewhere around 75/25 mix percentage by weight.

I am using Borax soap for flux and now understand less is better for the life of the crucible. In a A-8 crucible, doing a 14 pound pour, How much flux should go in? Also when? I have been putting it in when I place the cold metal in the crucible prior to lowering it into the furnace.

Another good question: When should the metal be put in the Crucible? I have been charging the crucible cold on the bench and placing it in the furnace after it is up to heat. Being oil fired I let it get hot and running steady before I place the crucible into it.

Well I have to cut this short, the wife is hauling me to the doctors office for a check up this morning.

By the way, watch this guy Grantham. He may be a thread pirate.

[steamin10]

This is where I complement you, as you have learned a proceedure, and generally follow it. Doing the same thing, in ritualized moves, adds to consistancy. Even a wrong move, takes you down the same path each time, and you learn to work with the details.

Ok, I think that charging a cold load of scrap to a hot furnace is a tad risky for the vessel, Metals expand when they heat, and this is reported to cause undue stress when the jambed in pieces press on the vessel walls. I know a full cold vessel like a cold heat will break a vessel, I have done it. But my experience is the crucible will get plyable enough before any real damage occurs. I try to run at least 3 heats when I cast, so that my furnace is hot and running, no preheat time, and molding of simple parts occurs while the metal is heating. Usually there is a puddle in the vessel, and the new charges weighed out and bucketed on the floor waiting for me, melt quickly as the heat transfer is much better when the charge is put onto the liquid remains of the last heat. This removes a pig move too. Never leave a part of a heat in the vessel to freeze, it is asking for trouble. Always pig the final remains.

I flux the heat lightly with every charge, as it helps the pieces flow together and cuts some of the dross causing oxidation. I have bagged Borax, but I know the laundry soap is not as good , but works, as the metals seem to ignore the scents and other junk in there, as it chemically breaks down the surface tension of the melting scrap, and bonds to the junk and helps it float out of the melt. Actually I flux twice, depending on how dirty the scrap was, how much plating I have to deal with, and like that. Once when I charge it gets some more or less, judging by dirt, and at the final moments before pour, flux and additions, degass-stir, skim, pour. So the fluxing is a judgment call, for me, virgin metals get almost no fluxing. Like so many things there are hard and fast rules in someones head, but in practice you make adjustments by experience and what you see in front of you. A SWAG. Exact proportions demand weighing everything. If you work with general scrap, you start out winging it, and sharpen your judgment as you go.

C Pipes has done a materful job at getting going from scratch, and has learned much, and still he questions as he thinks about the next moves. Courage! It is just running out the ritual, again and again, for all those parts you want or need. Pick off a coupla casting books, and you can get a contrast between dull Navy instruction, and some guy that cast for 30 yrs, like Ammen. I like you, are an ameteur trying to get somplace else with my castings.

Laters..

[steamin10]

A thought on piggin out.

When working from general scrap, as I mostly do, I avoid making pigs just for the sake of making a bar of metal. I pig what is left of the heat after the session of 1-4 heats and pours. I pour more aluminum from a #16 vessel, my brass vessel is probably like yours a #8 most likely. Anyway, some people melt what they have on hand to make nice little bars of metal. As you can see long term storage of piles of junk around the shop is a problem. So these bricks of value have the disadvantage of drift, being melted and cast, with all the oxides and gas and possible problems induced. This renders any metals more expensive due to fuel cost and wear, and your valuable time to run these off. The only real advantage is storage, and the view that if the metal is clean, you can see any varience in color that may indicate drift from the master alloy. A stroke of a file can always give you an idea of hardness, and true color below the skin. In some cases where the scrap is nasty, a pig will remove the gas, and lower the tendancy to porosity.

So if these facts seem to work against each other, they do. But mind you , these are the details we work with, and where you want to go with your castings, will dictate what you do to get there. That is the experience no one can tell you.

[steamin10]

A thought on scrap: House scrap you have on hand from turning and drilling brass, is probably the worst material to depend on for making a sound casting. Better to commit the clean brass, (no steel or other swarf) to a bucket and sell it to the dealer, or trade wight for lumps of what you want.

This is especially true if you venture into aluminum. Take those bags of cans and trade them for heavy casting, or wheels, whatever, just not thin sheet and things that wither to a dead winter leaf, and is of no value to us in a furnace.

GI-GO, the old computer term applies here. Garbage In - Garbage Out. Starting with a better brand of garbage is a leap toward a better result. Make the trades and start at a better level for a greater brand of success.

[Pipescs]

Not sure of what your meaning on the first heat as to the crucible.

Is it better to place the cold crucible in the furnace from start up and then add metal?

[Pipescs]

Grantham

I have received my birthday present and will use them in my next casting session.

I plan on using a lot of junk brass to do another cylinder casting so I will have a spare. As it will be a painted/Bondo covered piece on the PS-4 it does not need any particular strength but will require a lot of machining and tap work to bolt it all together.

I will also be trying some of Dave's inputs. Such as adding Zinc and Lead.

Dave.

You mention the zinc burning off as a white vapor. I have never seen this at Fenders (Charcoal) or here on my furnace. I am assuming on my oil fired furnace that it is lost in the darker smoke that my oil fired furnace generates in various amounts. This depends on my oil air flow which I have still not mastered on any given day.

The next match will be more to the Twenty-five/seventy-five mix as that is what I have laying around.With those thoughts I thought I would add around 10% Zinc and a few 1 oz. pellets of lead to a fourteen pound charge of items that have been thru the pot at least once. Some twice.

[Pipescs]

As this thread flows out, the undercurrent of cost comes out , that this hobby is by no means free.

By the way this is so true. Trainman and I had quite the discussion on the cost of having someone take you patterns and casting the part verses you doing the furnace route and doing you own.

I firmly believe you will never be able to do castings consistently or cheaper than the pro shops.

But on the other hand, earlier this month I needed an unusual shape to machine out a set of valve glands for the Rust Bucket project. It took an hour to rough out a wood pattern, and two hours with the furnace to have a part in my hand.


The bronze was left overs from a previous project, the oil in the furnace was free from the deep fryers at the local High School. All it took was my time and that is what the hobby is all about to me.