Member postings for PatJ

It should be noted that you can often cast a number of smaller castings in the same flask, and so the $6.00 per casting adder refers to castings that are so large that they take up an entire flask.

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John Campbell makes the arguement that the methods used in most foundries today do cause a lot of defects.

Others have show that if John Campbell's methods are adhered to, they can indeed make flawless castings, certified via xrays, scanning, etc.

The casting industry does not want to change their methods.

There are some very good new methods out there that have been proven to work well.

It does not cost any more to follow most (if not all) of John Campbell's methods.

But John's 10 rules for good castings may seem not that significant, they can make a huge difference in casting quality.

I think the problem with the castings made for this hobby (from what I have heard) is that they are often created at the end of a commercial foundry production run, and done in haste, without particular care.

The hobby casting business does not make enough money for the commercial foundries to bother with, and so most won't even consider them. Commercial founries are basically doing the hobby folks a favor.

I know from personal experience, and experience I have seen with others, that iron castings with a hardness of tool steel, and castings full of holes and inclusions are not really worth dealing with, unless you like to use a lot of JB weld.

The cost of the methods I use is not very much more expensive than any other foundry system.

I do use resin-bound sand, and ceramic mold coat, but the cost per castings on those items is not extreme.

I would guess the resin-bound and and ceramic mold coat, along with OK85 commercial sand probably add $6.00 per casting, but even if it added $12.00 per casting, that would be well worth it in my opinion to get high quality castings.

I have seen others get superb results in iron and aluminum with either green sand or Petrobond (oil-based sand).

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Backyard Casting "Mythbusters" of Youtube:

I have seen more than a few folks on youtube who "prove" that you can make quality metal castings by ignoring the fundamental rules for making quality castings.

In a hobby setting, which rules should be used?

There are no hard and fast answers; the methods and materials that you use should be the ones that work well for you.

I generally use a method or material consistently until I find a better more consistent or more reliable method.

If I am using a method, and it is working well, I don't change that method.

The problem with some youtubers is that they use a non-standard casting method, and pull off making a good casting, or perhaps what looks line a good casting from the exterior, and then use that as "proof" that you can make good castings using poor methods.

While it may be true that you can make a good casting using a poor method, it begs the question "Why not just use a better method if it is available".

I guess "better method" can be a bit objective.

What is a "good method"?

My definition of a good method is one that repeatedly and consistently create castings without defects.

My definition of a good method is also one that can easily be proven to be repeatedly effective, ie: section your castings and examine the interior for defects and consistency in casting thickness; drill the metal to test machinability, and break gray iron castings to look for a nice clean gray surface without chills (white spots).

Is there more than one "good method".

Yes indeed.

Are there a lot of bad (counterproductive) methods demonstrated on youtube?

Yes indeed.

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Edited By PatJ on 22/08/2022 19:46:37

Nigel-

I made a lot of bad castings before I got it figured out.

There is no reason for anyone to repeat all of my blunders, and so I am sharing what I know.

As for UK foundry terminology, I can't help with that.

I think John Campbell's book uses the terms that I use, and he is from the UK.

I have seen people pay good money for defective castings, and have done so myself.

All I can say is that castings defects are totally avoidable, both on the commercial and hobby levels, if one pays attention to details.

My castings don't have defects.

No gassing in aluminum castings.

No inclusions, hard spots, void, bubbles, chills, etc. in my gray iron castings, and very machinable gray iron castings.

I can help anyone trying to learn hobby casting, and save you a lot of headaches.

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Edited By PatJ on 22/08/2022 19:26:57

Pour Basin:

Pour basins are one of those things that have been used forever, and so it seems almost impossible to talk anyone out of using them.

I don't use a pour basin, but rather pour the metal directly down the sprue, with the crucible as close to the top of the sprue as practical.

You should fill the sprue as fast as possible to the top, and then keep the sprue completely full during the entire pour.  If you interrupt the pour before the mold cavity is completely filled, chances are you have aspirated air into the melt, and perhaps caused a cold joint inside the casting.

I use 1" section of 3" diameter heavy wall pipe above the sprue, and sometimes above riser openings.

The section of pipe acts like a pour basin to some extent, but also acts a a dam, to catch the metal when the mold gets completely filled, and to keep molten metal from running across the top of the mold.

The traditional pour basin is the base way I can think of to churn slag, air, and sand into the flow of metal, and ruin a casting.

People sometimes cling to their pour basins because "that is the way it has always been done".

And a lot of castings have defects too, but that is not a reason to keep making castings with defects.

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Edited By PatJ on 22/08/2022 19:20:43

Traditional vs New Methods of Metal Castings:

John Campbell makes the point in his book that the traditional methods that have been used to make metal castings for many years are generally very bad methods, and should not be used.

After making my own castings using John Campbell's methods, and studying the castings made by others who use John Campbell's methods, I am convinced that John is right on this point.

Most of the traditional methods and sprue/runner/gate/riser methods should never be used, unless you want routinely defective castings.

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Vents:

There is some debate in backyard casting circles about venting a sand mold.

Some use sand that has enough permeability to allow the vents to be omitted.

I have had resin-bound molds trap large air bubbles at the top of the mold cavity, and so I always use vents at the high points of the mold cavity, in the cope or top half of the mold.

I make vents using a 1/16" diameter steel wire, which I poke from the interior of the mold out through the top of the mold.

I also vent my cores.

If my core is round, I normally make the core with a 1/4" wood dowel rod inside, and then withdraw the dowel, to leave a 1/4" passage through the core.

I use vertical vents from both ends of a core, 1/4" diameter, and these vents extend out the top of the mold.

I flame my cores lightly with a gentle propane flame.

Alternately, cores can be baked to drive off any residual moisture.

Many castings get ruined because the core was not vented or dried correctly.

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Where do the gate(s) go?

Gates are often used at the thickest part of the casting.

If you use gates at the thinner parts of the casting, the tendency is for the metal in the thin part to cool and solidify before the thicker parts of the casting have fully filled.

If possible, use gates at a part of the casting that has to be machined, so that the gate is eliminated after the machining work is complete.

For symmetrical castings (ie: somewhat square-shaped castings), I genrerally use one or two gates.

For long rectangular shaped castings, I often use multiple gates down the side of the casting, and often knive gates, which are gates that are wide and flat.

Try to locate gates on the casting where they can most easily be removed after casting, keeping the above in mind.

I use gates located at the top of the runner.

The idea behind the gates at the top of the runner is to allow the trash and aspirated air to flow down the runner to the end of the runner (ideally flowing into a spin trap).

The mold cavity does not begin to fill until the runner is completely full.

The gates provide one last skim of slag that may be floating on top of the molten metal.

If the gate is located at the bottom of the runner, all the trash is swept right into the mold cavity.

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Edited By PatJ on 22/08/2022 19:10:43

Try to make the thickness of your casting consistent and constant.

If you look at sections of the old steam engine cylinders, you will see that almost every part of the cylinder has the same wall thickness.

You get even solidification when you use a constant casting thickness, without hot tears.

If you can't avoid using uneven casting thicknesses, you should consider using one or more risers, which allow you to avoid the small part of the casting solidifying first and drawing metal from the parts of the casting that are still molten.

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One of John Campbell's rules is avoid waterfalling the metal into the mold.

If you have a tall mold, you should not introduce metal into the mold cavity in a way that causes the metal to run a long distance down vertically to the bottom of the mold cavity.

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I have studied John Campbell's "10 Rules for Good Castings" for several years, and also studied the work of those who have successfully applied John's rules, in order to make flawless castings.

Some of the 10 rules are more critical on a hobby level than others.

Rule #1: Use quality scrap metal of a known composition.

I would add that you should use metal that will work well for the particular casting you are making, such as using bearing bronze for bearings, instead of some metal that has a very high stiction (don't ask me how I know this).

Velocity:

Probably the most critical thing in metal castings is controlling the velocity of the metal as it travels down the sprue, through the runner(s), through the gate(s), and into the mold cavity.

If you don't control your metal velocity, you basically get something similar to what happens with waves breaking on the shore. The metal folds over on itself like a wave, and then churns sand, air, slag, etc. into the molten metal. Churring/folding the metal as it flows should be avoided at all cost.

Metal velocity can be controlled several ways.

Some use the sprue as a choke to limit the metal flow rate.

Some use the gates to control the flow rate.

Some use ceramic sponge filters located either at the base of the sprue, or inline with the runner, to control flow rate.

I use the gates to control metal flow.

Mold Fill Rate:

The mold cavity should be filled as fast as possible, but not so fast that you cause splashing or turbulence of the molten metal.

You are basically looking for a laminar flow of the metal, where the wavefront of the molten metal as it travels down the runner and through the gates is never broken.

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Lets talk about definitions for metal casting, especially as related to hobby backyard castings for model engines, with a bit of preface.

I have seen some superb and basically flawless gray iron and aluminum model engine castings kit castings, and I have also seen casting kit castings in gray iron that were very expensive, but full of blow holes, and not really suitable for any engine use.

It seems to be accepted that castings with serious defects, and gray iron castings with chilled (very hard) spots in them are part and parcel to the hobby.

I am here to say that if I can make aluminum and gray iron castings without defects, and without hard spots, then everyone in the hobby should expect that the casting kit companies should also be able to do so when using "professional" foundries.

I have learned the metal casting hobby over the last 10 years, and I will share the secrets of making successful model engine castings.

But we need to discuss definitions first, and so the following:

Note that this is my slant on casting definitions, and perhaps not an exact thing.

1. Sprue: The sprue is the hole in which you pour your molten metal.

The sprue should be tapered, and should be small enough in diameter so as to fill quickly, and remain full at all times during the pour.

2. Pour basin: Many use a pour basin on the top of the mold, and they pour metal into the pour basin, which then overflows into the sprue.

Sometimes a basin is also used at the base of the sprue.

3. Runner(s): Runners are the horizontal passages that transmit the molten metal from the bottom of the sprue to the mold cavity. Runners are often V-shaped, probably since this makes it easy to withdraw the runner pattern from the sand mold. Runners are often located at the cope/drag interface, either in the cope, or in the drag. The cope is the top half of the sand mold, and the drag is the bottom half of the sand mold.

4. Gates: A gate is the passage or passages from the horizontal runner into the mold cavity. The purpose of a gate is to control the flow of metal into the mold cavity, introduce the molten metal into the mold cavity at the entry point(s) that you desire, and to skim the molten metal so as to catch any floating slag.

Gates can be many shapes, but are generally rectangular in shape, or sometimes a wide thin rectangle such as with a knife gate.

Knife gates are used when the casting is thin, such as with a plaque, and they allow the mold cavity to fill quickly across a wide area.

5. Riser: A riser is a chamber (void in the sand mold) located at strategic spots, with the intent of furnishing molten metal to a part of a casting while it is shrinking and soldifying. Often risers are used when the thickness of a casting is not uniform, so that you don't have the thin part of a casting solidify first, and draw metal from a thicker not-yet-solidified part of the casting; thus causing srhinkage defects and hot tears.

6. Hot Tear: A hot tear is what is sounds like. If part of a casting solidifies before the rest of the casting solidifies, it can create forces in the junction between these two areas, and the result is tears in the metal.

7. Inclusion: A n inclusion is something imbedded in the metal casting that is undesired, such as a piece of the sand mold, slag, etc.

8. Bubbles: Bubbles and similar round-edged defects in castings can be caused by absorption of hyrogen or other gasses in aluminum, too much water in the sand mold, resin molds that are not fully cured and flamed, or pockets of trapped air at the top of mold cavities that are not vented.

Bubbles can vary in size from very tiny pinhole size, to inches in diameter.

9. Spin trap: A spin trap can be used at the end of a runner, and it is a vertical shaft that often leads out the top of the mold. The purpose of a spin trap is to capture the initial debris that gets washed down the sprue and runner, capture any initial aspirated air that was mixed into the molten metal while the sprue was filling, and to prevent the molten metal from striking the end of the runner and splashing back into the mold cavity.

10. Cope: The top half of the sand mold.

11. Drag: The bottom half of the sand mold.

12. Flask: The wood or metal box into which the sand is rammed.

A flask often consists of two parts, which make the cope and drag molds.

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I found an automated-voice valley girl tutorial for SE.

This must be the one Nigel is referring to; and I agree, totally annoying voice by any measure.

The problem I found when trying to learn 3D modeling is that the tutorials are not very focused, and they are often an advertisement for features.

I found Solidworks to be terribly intimidating, until I found out that I basically only use about 10 commands over and over again, and perhaps 90% of Solidworks I will never need or use.

I found the Solidworks tutorials incredibly frustrating, and there were no tutorials on how to best 3D model an engine such as we build.

I swore off learning 3D modeling over and over again for about a year, and finally got enough traction where I could start learning to make primitive 3D models.

I could sit behind someone and teach them 3D modeling in about a week I think, a few hours per day.

I had to teach myself; I did not know any tutors.

I highly advise you to ignore synchronous mode, and stay in the standard mode (I forget what SE calles non-synchronous mode).

Once you master standard mode, then consider learning synchronous mode.

If you get in a pinch with standard mode, then I or many others, regardless of what software they use, can probably help you.

If you start using synchronous mode, you will lose a lot of help from folks who don't use that.

For me, learning 3D modeling was like carving a statue out of granite.

You chip off a few pieces every night, and make little progress for a long time.

Suddenly a shape begins to appear, and you start to figure out what it is you are suppose to be doing.

Once you figure out the basic 10 commands that you generally use, then you wonder "why did they make it seem so difficult in the tutorial?".

The answer is they are trying to sell features, and the more features they announce, the more money they can charge you. It is a features-race between the other software companies, but as I mentioned, 90% of the features you will never need or use.

When creating my 2D sketches, I use typical 2D drawing tools, such as line, trim, offset, circle, etc. (basic shapes). I start by opening a new PART file.

When I get my sketch done, I toggle over to 3D mode, and use a 3D command to do something with the sketch, such as extrude, cut, revolve, etc. and I make some sort of 3D solid shape from that 2D sketch.

Rinse, repeat, rinse, repeat.

Its the same thing over and over.

Go to 2D mode, make a sketch, toggle to 3D mode, extrude or cut with that sketch.

That is almost all there is to it.

Making 2D drawings in Solidworks involves opeing a DRAWING file, and dragging and dropping a 3D shape onto the sheet, where it creates a 2D front view, and then dragging that view up, down, sideways, and diagonal to create a left view, right view, top and bottom views, and isometric views.

Save your 2D sheet and print it.

I create one PART file at a time, for each piece of an engine.

Once each part files is done, I create an ASSEMBLY file, and drag and drop each part into the assembly, one at a time, and then mate then in the correct orientation.

My brother saw a screen shot of my Solidworks, and he said "Boy, that sure does look complicated", and I said "If you knew how few commands I actually commonly use, you would not say that".

It looks a lot more complicated than it really is.

I can definitely relate to your frustration though.

Been there, done that, banged my head on the wall for a long time; but I learned it in the end.

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Edited By PatJ on 22/08/2022 03:36:13

The resin binder I use is an alkyd phenolic resin.

There are ester-cured-phenolic resins, phenolic-polyurethane resins, and many more, so while I don't know exactly what epoxy is, my guess is that it may work ok.

I have seen some try epoxy as a binder, but never heard back on the results.

Keep in mind that the resin binders have a "set" time, and a "strip" time.

The set time means the mold has hardened, but not completely, so keep it on a flat surface for a while.

The strip time is when you remove the pattern from the mold.

If you exceed the strip time by too much, the bond is too strong, and you have basically permanently glued your pattern into your molding sand.

I use a 3-part resin binder, which is resin/hardener/catalyst.

The bulk of the binder is resin, which is 1.5% of the weight of the sand mold.

My hardener is a lesser amount, which is 20% of the weight of the resin.

The catalyst is optional, and can be used to adjust the set time anywhere from 1 hour or more, to 5 minutes.

So perhaps an amount of epoxy slightly more than 1.5% in your sand ?

The epoxy I have seen in liquid form is usually mixed 50/50 (1:1 ratio).

And with resin sand, once the mold has set, I lightly flame the interior of the mold with a gentle propane flame.

I would assume you would not want to breath the fumes when you flame the mold.

I am not positive about flaming an epoxy binder, but with a resin binder, it basically burns off any uncured resin, and gives a better surface finish.

I hope this info is applicable and helpful.

Good luck.

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A few notes on bound sand.

Resin bound sand is pretty difficult to find, and you have to use it with very dry sand (sand that has been baked to drive off the moisture, so I am told).

Sodium silicate binder is much easier to find, and does not seem to require a commercial chemical respirator like the resin binder does.

Sodium silicate sand is very sticky, and so use plenty of wax on your pattern.

I am not sure if your rod ends have draft on them, but they would probably need 3-5 degrees draft.

Sometimes you can get away with little or no draft with bound sand, especially if the pull is short.

I suspect the big end will solidify last, and so without a riser at the big end, you will have shrinkage there.

Normally any two surfaces at 90 degrees need a fillet, to get a clean pull from the sand mold.

I am not seeing any fillets, and so that could be a problem.

Many home foundry folks use the mold cavity as a runner. I consider this not an optimum method, but people do use it; it can work; and it minimizes the crucible and melt size required for a given part.

I have often heard that the gate should enter the largest part of the casting.

You could try a gate on the big end, and let it feed big end to small end.

I would slant the mold so that the small end is elevated a bit, so the mold fills up towards the small end.

I would use a small vent hole on the small end, and perhaps on the big end, with the vent hole going out the top of the mold.

Be sure to clamp or weight the mold, so hydralic pressure does not force the cope up off the drag.

A second approach would be to have a runner parallel to the rod, with a long knife gate into the thin part of the rod. This approach required more melt metal, and perhaps a larger flask, and I am not sure it would work correctly, given how big the ends are.

Good luck.

P.S. - If you use sodium silicate sand and CO2 to set it, be sure you don't over-gas the sand (5 seconds of gassing only).

P.S. 02 - I don't use a pouring basin, as they seem to aspirate air.

Sometimes I use a metal ring above the sprue, to make a pouring basin of sorts.

Keep the lip of the crucible as close to the sprue opening as possible, perhaps even letting the crucible touch the sand (don't break off the sand though). Fill the sprue as fast as possible, and keep it full during the pour, without interruption. Practice pouring water if you need to refine your technique (its not a linear thing; you pour faster at first, and then the flow slows down when the sprue is full).

Watch for when the vent holes fill up with metal, and be ready to stop pouring when you see metal come out of the vent holes.

Keep the sprue as short as possible so as to keep the metal velocity as low as possible.

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P.S. 03 - I use a foundry cement to seal the cope to the drag, when using bound sand, to prevent runouts.

Pour temperature should be around 1,350 F (732 C).

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Edited By PatJ on 21/08/2022 19:39:42

Somehow I got a duplicate here.

Edited By PatJ on 21/08/2022 19:35:46

Dave-

That is a great explanation.

Thanks for that.

Pat j

It is an odd thing, but I cannot melt 1/2" mild steel rods in my crucible steel furnace.

But if I use a 1/2" mild steel rod as a skimmer, or stirring rod, and stir the melt while it is at pour temperature (pour temperature is between 2,500 and 2,600 F), if I leave the rod in the melt for more than about 30 seconds, the end of the rod almost completely melts off.

Someone mentioned that there is a chemical reaction between the mild steel rod and the molten iron, which is why the steel melts.

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I have read some old casting books, and also John Campbell's book on castings, and the No.1 rule of making quality castings is to start with quality scrap that is of a known composition.

Items like window sash weights are made from the discards from the casting process, and the old book specifically mentions avoiding junk metal like window sash weights at all cost.

I have heard that cast iron radiators should also be avoided in engine castings, due to the phosporus, but then I saw a fellow cast a model V-8 engine block in gray iron made from radiator iron.

The phosphorus gives the iron excellent fluidity, at the expense of I think strength.

It would appear that on a model engine scale, using phosphorus radiator iron does work ok, but I am not sure how you would test what "ok" is.

The V-8 does function well.

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I have heard various comments on the suitability of disk brake rotors for making iron castings.

I know of one individual who uses disk rotors exclusively, but I have not had an opportunity to test any of his castings.

He does add the extra step of annealing (I think that is the correct term) all of his iron castings in a kiln.

I have never had to anneal any of my castings when using electric motor end bell housings.

Ferrosilicon can also improve the machinability of ductile iron, when ductile iron is used as scrap (so I have heard).

The amount of ferrosilicon that is added to an iron melt is critical.

Too much ferro and you get excessive shrinkage and hot tears.

The correct amount of ferrrosilicon improved fluidity, and prevents hard spots in thin sections of castings.

The correct amount of ferrosilicon to be used with iron is very small, such as 0.04-0.06 oz/lb of iron.

I add this amount of ferrosilicon to all my iron castings, but you only really need it for castings that are thinner than about 3/4".

As I understand it, when you melt ductile iron, it basically reverts back to gray iron (perhaps not entirely).

The difference between ductile iron and gray iron is the distribution of the graphite.

Chilled thin gray iron castings are basically the hardness of tool steel, and cannot be drilled with a normal twist drill.

Another secret to good machinable iron castings is to let the casting cool in the mold overnight, and cool as slowly as possible.

Aluminum 356 benefits from a water quench, but you never want to cool iron castings quickly, unless hardness is desired in the casting, such as in a high wear situation (such as the teeth on an earth moving bucket).

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