# My latest bar 3.175 Troy ounces - I wish I could keep it!



## kadriver (Dec 23, 2010)

Here is a picture of my latest bar that I completed last night

It weighs 3.175 Troy ounces.

It has a little frost and two spots of slight discolor on the top.

I would love to run this back through the entire process (except inquarting) to see If I can get it just a little cleaner.

But - I must send it in to the refiner and get some cash flowing  

Please feel free to be critical about this bar - I want to learn all I can from this forum.

I refined this bar one time. A second refining would probably make it look much better.

Thanks - kadriver


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## skeeter629 (Dec 23, 2010)

It looks fantastic. Awesome job!


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## Barren Realms 007 (Dec 23, 2010)

Looking good.


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## patnor1011 (Dec 24, 2010)

Looks much golder than your wedding band 
Nice work.


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## Platdigger (Dec 24, 2010)

Nice!


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## philddreamer (Dec 24, 2010)

Oh yeah! 8) 

I just melted a 1.2 oz button today, too. Seems like they come in groups.  

Phil


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## Platdigger (Dec 24, 2010)

Hey, you should make that third pic from the top your new avatar.


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## Harold_V (Dec 24, 2010)

For a single refining, it's quite good. Please do note that the slight frosting appearance is likely a contaminant of sorts, although unlikely to be copper. A second refining would definitely improve the quality, but for sale to a refiner, there's absolutely nothing wrong with what you've done. Nice work!

Harold


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## Oz (Dec 24, 2010)

I agree, fine job!

Not that it matters when selling, but you asked for critique. You would have less of a lumpy look or grain to the sides and bottom of your bars if your mold was a bit warmer before pouring. If you are using a graphite mold I would not change a thing as it will decrease its useful life. But if you are using an iron mold, there is nothing wrong with pride in craftsmanship. You do cast nice looking bars.


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## silversaddle1 (Dec 24, 2010)

I wish I could get my hands that clean! :lol: 

$4394.20.....nice!

Merry Christmas!


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## kadriver (Dec 24, 2010)

Thanks all.

I am using a graphite mold - 4 cavity - 1oz, 2oz, 5oz, 10oz.

If I use an iron mold, would I get a better looking bar?

I place and hold a propane torch on the graphite mold for at least 5 minutes before I pour the gold. I leave it on the mold as I melt the gold. Then, just before I pour I turn the propane flame away. Plus I hit the graphite mold for a few seconds with the oxy/acet torch just before I pour.

I am happy with the bars, but I know there is room for improvememnt - any suggestions would be welcomed.

Thanks & Merry Christmas!

kadriver


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## kadriver (Dec 24, 2010)

I think the avatar suggestion is a good one, I may do it.

Thanks


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## AuMINIMayhem (Jan 20, 2011)

looks great!

I have thought about trying making a S.S. 304 mold and using a light coating of carbon from an oxy/acetyl torch rather than using a graphite mold. From what I've read it seems to make for a better mold release. Also, heating your mold that long (5+ minutes) may be causing the graphite to "outgas", which could result in bubbles and voids, particularly on the bottom side.

These are just things I've read and haven't had the opportunity to try personally. I believe Lazersteve was one person I read who had suggested using the Acetylene (spelling?) carbon as a mold release.. I could be wrong, but his name sticks out for some reason.

Anyways, wish I had that beaut in my position! Great job! :mrgreen:


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## Harold_V (Jan 21, 2011)

AuMINIMayhem said:


> I have thought about trying making a S.S. 304 mold and using a light coating of carbon from an oxy/acetyl torch rather than using a graphite mold


You'd be miles ahead to make the mold from ductile iron, which is much easier to machine, and less prone to soldering. Second choice would be gray iron, which doesn't have the heat shock resistance found in ductile, but has served well for years as ingot molds. I agree---a graphite mold leaves a great deal to be desired. 

A smoky acetylene torch is the best possible way to coat a mold, and I agree with your assessment on gassing. Even a torch smoked mold will gas if the gold is too hot, or if the mold is preheated too much. There's a delicate balance where the soot isolates the gold from contact, and doesn't cause problems. I found that a cavity that is used twice often yielded the best results, although you also risk soldering to the mold if too much of the soot has been consumed. 

Harold


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## AuMINIMayhem (Jan 21, 2011)

iron?... hadn't thought of that, but I think you're probably right on with that the more I ponder it. :idea: 

I had tried a very small (1 gram) mold I made out of 304 one time, the biggest problem I had with stainless is that it gets "tool hardened" with high heat which makes it more brittle, not so much as a mold, but brittle as in if you dropped it, it might shatter..

the plus side of stainless though was that it can be machined soooo smoothly that mold release is almost a non-issue..

I do have a chunk of grey iron in the shop.. maybe I'll give that a shot within the next few weeks (time permitting) and I'll let ya know how it went. 8)


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## wrecker45 (Jan 21, 2011)

what about a peace of channel


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## Harold_V (Jan 21, 2011)

AuMINIMayhem said:


> I had tried a very small (1 gram) mold I made out of 304 one time, the biggest problem I had with stainless is that it gets "tool hardened" with high heat which makes it more brittle, not so much as a mold, but brittle as in if you dropped it, it might shatter..


That is one of the negative qualities of stainless---although the reason isn't work hardening. That would be an issue while machining, no doubt, especially if you used somewhat dull tooling and took cuts that are considered too light, with modest feed. 

The problem with most grades of 300 series stainless is it's quality of intergranular corrosion, which occurs between 800° and 1,500° F. Considering the mold would experience temps in that range on a regular basis, it's entirely possible it could fail from brittleness. With that in mind, one would be best served to use 316L or 317L instead. The L in this grade of stainless represents a low carbon content. 

Assuming one insisted on the use of stainless, there are other options to overcome the intergranular corrosion problem. 321 stainless has titanium included, and 347 includes columbium and tantalum for the purpose. Overall, one is still best served to use ductile or gray iron. Each of them machine well (although dirty due to free graphite) and serve perfectly well. A seasoned cast iron or ductile iron mold should see one through a life-time of casting.



> the plus side of stainless though was that it can be machined soooo smoothly that mold release is almost a non-issue..


Considering a mold should be well blackened before pouring, that's usually not an issue. To insure release, molds are typically made with draft, so unless a very poor end mill is used for the cuts, release is pretty much guaranteed, even when providing very little draft. What's really important is that there are no undercuts, to which the pour can key----and that the mold is well covered with soot----which prevents soldering. 



> I do have a chunk of grey iron in the shop.. maybe I'll give that a shot within the next few weeks (time permitting) and I'll let ya know how it went. 8)


Do that, and do let us know how it goes. 
I suggest you buy a tapered end mill. One with three degrees per side taper should serve the purpose well. Pick one that is relatively small in diameter, so your (small) ingots look good. A huge corner radius doesn't look good at all. Be advised, you'll most likely have to radius the flutes at their end, so the bottom surface of the mold has a radius. You can do that by hand, using a radius gauge as a guide. It takes a little attention, but is very doable. I did all of my molds that way. 

If you choose to use gray iron (or ductile), it's a good idea to machine all faces before starting the cavity. Remove all scale, which often included traces of sand. The slightest amount of sand in the iron will ruin the tapered end mill. 

Good luck!

Harold


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## AuMINIMayhem (Jan 22, 2011)

that wouldn't be a problem.. that's what I do is machine work for the space industry.. I regularly machine flight-critical parts to within tolerances of 5 decimal places 8) (sorry gotta be vague for a reason)... never machined grey iron before, would you suggest a tungsten carbide end-mill?.. :?:


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## Harold_V (Jan 22, 2011)

AuMINIMayhem said:


> .. never machined grey iron before, would you suggest a tungsten carbide end-mill?.. :?:


If you remove all cast surfaces (and it's not chilled), it machines perfectly well with HSS. If they're sharp, performance is very acceptable. Unless you intend to make a number of molds, I think I'd advise against paying for carbide. C2 grade if you must.

If you have access to CNC (I expect you do have, based on your comments), there's no reason why you can't use a carbide ball end mill, 1/8" or maybe a 5/32", and create draft by programming accordingly. That way you don't have to purchase a tapered end mill. Just a thought. 

Harold


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## AuMINIMayhem (Jan 24, 2011)

Harold, I don't have a CNC, I do it all on a Bridgeport. 8) 

Cost for carbide end mills is a non-issue, I have end mills coming out my ears, I have Titanium Nitride, Cobalt, and Carbide sets in two and four flute, ball end and bottom boring I even have a set if left-hand spirals. 8) We machine all kinds of metal: SS 416, 303 and 304, Aluminum, Molybdenum (Moly), Titanium, Beryllium, and Invar (known around these parts as the "1st class son-of-a-you-know-what" to machine.. :lol: )

I'm thinking for grey iron I could go with a two-flute Ti-Nitride end mill with a good dose of oil and I could get a nice mirror finish after a seemingly endless number of passes... but that's what I do anyways. 8) (I machine mirrors, flexures and shims for satellites, so my work is very precise even by machinist standars)


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## Harold_V (Jan 25, 2011)

AuMINIMayhem said:


> Harold, I don't have a CNC, I do it all on a Bridgeport. 8)


Then a tapered end mill is really in your best interest. Otherwise in order to get draft you'll have to tilt and nod the head repeatedly, or index the mold. Corners will be a real bitch. That leaves the door open for undercuts that aren't desirable. You really want an ingot to look good. With a CNC, you can do all that with programming. 

I find it rather strange to be talking like that considering my entire machining career was based on manual equipment, pursuing small precision work, primarily for the aero-space, defense and pharmaceutical industries. Amazing how owning a CNC mill for a short period of time changes one's thoughts. I purchased a Haas TM-1 mill ---built in 2004. I'm hardly literate, but it sure makes things go easier with what little I know. 



> I'm thinking for grey iron I could go with a two-flute Ti-Nitride end mill with a good dose of oil and I could get a nice mirror finish after a seemingly endless number of passes... but that's what I do anyways. 8) (I machine mirrors, flexures and shims for satellites, so my work is very precise even by machinist standars)


If you have no experience with cast irons, you're going to find finish suffers. The free carbon (graphite) yields a rather uneven surface, due to the free carbon pockets. Ductile is slightly better, having spherical bits of graphite instead of flakes, but both of them cut with a rather dull surface finish, which is somewhat porous. That's not much of an issue in that if you us a cutter without uneven wear (no lines), when you blacken the mold for use, it all goes away, anyway. You can get wonderful finishes on the ingot if you master temperature and pouring/chilling techniques. 

Oh, yeah! One thing more. Cast iron and ductile should be machined dry. They make one hell of a mess when you include lubrication. The free graphite serves to lubricate enough. 

Do keep one thing in mind. Gold does not pour thin ingots. If your plan is to pour a large but thin ingot, the end result will be a partial ingot---for the gold will ball up before flowing out to fill the mold. Think of a loaf of bread when you make your design---although slightly thinner. Right off the bat, I'd suggest the ingot should be one thickness, width equal to two thicknesses, and length equal to three thicknesses. That will get you in the ball park, then you can work out what is best for your desires. You'll learn only by pouring the gold. 

I'd enjoy seeing what you create when you do, so please do post some pics. 

Harold


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## AuMINIMayhem (Jan 25, 2011)

Harold_V said:


> I find it rather strange to be talking like that considering my entire machining career was based on manual equipment, pursuing small precision work, primarily for the aero-space, defense and pharmaceutical industries.



Sounds like we're in the same line of work. 8) 



Harold_V said:


> Amazing how owning a CNC mill for a short period of time changes one's thoughts. I purchased a Haas TM-1 mill ---built in 2004. I'm hardly literate, but it sure makes things go easier with what little I know.



:lol: ...*somebody* got spoiled.. :lol: 



Harold_V said:


> If you have no experience with cast irons, you're going to find finish suffers. The free carbon (graphite) yields a rather uneven surface, due to the free carbon pockets. Ductile is slightly better, having spherical bits of graphite instead of flakes, but both of them cut with a rather dull surface finish, which is somewhat porous.



Yeah, I figured the smoother I can get the cut, the better...Obviously all metals have their limitations as to how "smooth" they can be machined, but I do agree with you that if I can get it to where the machining marks are minimal, then the carbon from blackening the mold should make for a very pretty pour.



Harold_V said:


> Oh, yeah! One thing more. Cast iron and ductile should be machined dry. They make one hell of a mess when you include lubrication. The free graphite serves to lubricate enough.



I could probably machine it without lubrication. There's quite a few things we have to do "oil-free" (Invar, in particular). Hadn't thought about that, but you are correct, the free carbon would act as a nice lubrication in and of itself.


I'm used to doing fine cuts, even when we have to take out large amounts of material, because we're constantly having to measure and re-measure as well as being careful no to heat the parts we're working on (CTE's can really screw you when you're maching to tolerances of +/- 0.0005" ). So, I plan on taking my time with this. It's more for fun than anything, but it would be nice if I got the chance to use it as well. Certainly not going to be a "mass production". LOL!

I'll definitely post pics when I get the chance. Wish we had some space on here rather than having to throw it up on another site to link it here. (or am I missing something?)

I did plan on making the mold in this sort of profile (I figure go with what works) and I could certainly see the value in having it more on the "deep" side than shallow as the gold would cool too quickly.

I was thinking of something along the profile of this:








rather than this type:






but, doing a couple of them in series like this:







I know I could easily purchase one and be done with it, but for me the fun is in making all these things, myself. I have the resources and the tools and it's fun. I certainly wouldn't recommend anyone else do this, it's not economical, nor easy. I just enjoy working with metal and it'd be a fun project. 8)

I'll keep you posted once I get some free-time on the machiness 8) 

Derek


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## Harold_V (Jan 26, 2011)

AuMINIMayhem said:


> I could probably machine it without lubrication.


I may not have emphasized that enough. If you lubricate, unless it's flood coolant, you end up with a nasty paste that tends to act like a lapping compound. Because cast iron machines in crumbles, it turns pretty much to powder. Ductile isn't quite as bad, even when it contains the same amount of free carbon---because the nature of the material permits chips to form instead of powder. Still, it's best machined dry. 



> I'll definitely post pics when I get the chance. Wish we had some space on here rather than having to throw it up on another site to link it here. (or am I missing something?)


If you mean that you can't post pictures on the forum, yeah, you've missed the boat. They are posted as attachments, which can be included on the same page on which you compose your post. Look below the box, and follow the simple instructions. I'm not sure how Noxx has the board set up (moderators are not able to access that portion of the board), but he may have it set such that you can't post pictures beyond a given size. Anything larger than 800 pixels in width spreads text for those with old cathode ray monitors, so make sure you don't post pictures that are too large. Otherwise some readers have to scroll side to side in order to read the posts. Once a picture is posted in a thread that's too large, all posts on that page are spread. 



> I was thinking of something along the profile of this:



It's obvious that the mold for that type ingot was cast. The extreme taper doesn't allow for machining without tilting and nodding the head of a mill, and corners, as I said before, become a nightmare. When you use a tapered end mill, the corner radius will be ever enlarging with depth, so it's a good idea to use one with minimal taper, which will yield a more straight sided ingot. They look good, but the corner radius does get larger with depth. 



> rather than this type:


That one, of course, is not cast, but die struck. That's a whole different world, and requires fine die work and a heavy press--100 tons or more. It's sort of beyond the average guy's ability. I've given some thought to pressing a one ounce ingot, but it would be small in width and length---because I have only a 100 ton press (not operational right now) at my disposal. Maybe some day! :lol: 



> but, doing a couple of them in series like this:



Be mindful of wall thickness. If you choose to make a multiple mold (I don't recommend it), allow plenty of material between cavities, so there's metal to absorb the heat. Remember, you'll pour gold at no less than 2,000°F, which will tax thin molds. They must be able to absorb the heat without getting red hot. 



> I know I could easily purchase one and be done with it, but for me the fun is in making all these things, myself.


Frankly, I'm not convinced you can buy one---and if you do, it will most likely be made of graphite. I'm not keen on that idea, if for no other reason, it degenerates with use. An iron mold, assuming it doesn't crack, will see you through years of refining and pouring ingots. 



> I'll keep you posted once I get some free-time on the machiness 8)



Looking forward to your results. Luck with the project (as time allows 8) )

Harold


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## Oz (Jan 26, 2011)

I’m just poking my head in here for a minute. I have learned much from Harold as to making precious metals molds. I hope you both keep chatting about it so I can learn more. I have plans to make a few as I have a Bridgeport mill now.


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## AuMINIMayhem (Jan 26, 2011)

Harold, yeah, I have a flood coolant attachment to my Bridgeport, so that's what I was originaly thinking of (it was just easier to type "oil", that's my mistake, I tend to forget to NOT abridge things on here, specificity is a preference on these boards.. my apologies on that 8) )

As far as tilting the head to get those types of angles, I wouldn't need to do that.. I have a quite the selection of sine plates, like this:






So, doing say a 65-70 degree draft on the sides would be easy-peasy-chicken-greasy.. :mrgreen: I do it all the time (usually in Al 6061, but I've done SS 304 and Invar as well)

If I were to do, say, 3 molds in one holder I was thinking of a wall and floor thickness of no less than 0.750", would you agree? I was actually thinking the floor ought to be aroun 1" and the walls seperating the molds at 0.750".

I love working in a place where I have limitless funding to buy all the tools and doo-dads to get the jobs done! :mrgreen: 

I wish I could post pics of some of the stuff I've done, but... :roll: yeah, if it's not classified, it's proprietary.. but I can post a pic of something "along the lines" of the type of stuf I do.. 8) )






This is a mirror and optical assembly for the JWST (James Webb Space Telescope) I haven't worked on that program directly, but the mounting brackets, etc. are VERY similar to the program I'm working on. 

On a side note, that mirror is a SiC mirror, we make those here. That whole process is extremely cool as far as how they've figured out to cast it, etc. (Unfortunately, it's super-proprietary, so I can't really get into it.) I just thought it was interesting how SiC is used for mirror subrates rather than something "metal". I always had assumed they were some sort of highly optically polished metal, but nope.. SiC is the wave of the future.. it all has to do with CTE's (Coefficient of Thermal Expansion).. 8) 

Oh boy... there goes Derek on one of his nerdy science side-tangents.. :roll: :lol: 


Seeing as I never have time (or gold) to do a melt anymore, would you (Harold) be interested in tryin' her out? I'd happily send it out to you and you could have it so long as you posted pics and perhaps a summary of your experience with it, critiques, etc. 

I just got thinking, I'm getting ready to take on this project for sheer "sh-ts-n-giggles" and yet I really wouldn't have the capacity, time or even the material (gold/silver) to actually put it to use to see if it worked..  :lol: 

I'll keep ya posted once Iget started on this.. 8)

Derek


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