Question about Delft clay casting (Smart Dog?)

[Hemo]

I'm about to start making a sideplate and escutcheon plate for an early (ca. 1700) pistol. Each will be pretty sculptured, with several perforations. I could make these out of thick sheet brass, but I'd like to try casting them with Delft clay. I have never done this, and need some advice.

I'm pretty sure I could do the escutcheon as a single piece. I know Dave Person (Smart Dog) cast a nice side plate in two or more pieces with Delft clay and soldered them together. Would it be possible to cast a sideplate in one piece with a larger mold?

Also, how do people melt their brass for casting?  In a crucible with an acetylene torch for a heat source? Or in a high temperature oven?

This is generally what I'm trying to create:


http://jamesdjulia.com/item/lot-2524-good-and-rare-pair-of-flintlock-holster-pistols-period-1690-1720-signed-g-frugone-49805/

Thanks for any info!

Gregg

[jerrywh]

 I never used Delft Clay but I have done a lot of lost wax and Petrobond casting and regular sand also. I see no reason that you cannot do the whole piece in one pour. When I pour I cast at least three at once and sometimes as many as 10 or 15.  Brass is more problamatic than silver. Silver is the easiest metal for casting. When melting brass care must be taken not to burn off too much zink. Brass should be melted in a way that will keep excess oxygen from the molten metal. The pouring temp for brass is around 1800°F.  I recomend buying a good book on casting and studying some before you do this. There are a lot of good books on the subject. I think Rio Grande has some. Notice the pyrometer setting on the table. This small crucible furnace does a great job.

[smart dog]

Hi Gregg,
That would be a wonderful side plate!!  The trouble with the Delft system is that the mold cools very quickly.  The sprue hole is usually located on the back side of the piece to be cast and the hot metal pours into the mold at a right angle. It hits the opposite side of the mold and then has to flow and spread out horizontally to fill the rest of the cavity.  That situation slows the flowing metal and cools it quickly.  That becomes a problem if your design is large and has many intricate and small channels.  Keep in mind, Gregg, casting my sideplate in 3 pieces and soldering them together was very, very easy and I designed the joints so there is no way anyone can see the solder.  That said, if you want to try a single pour, you might try a couple of things. It is easy to build a casting frame of the size you need.  It can actually just be made of wood with the top and bottom indexed to match in the same way by using some metal pins mounted in one half that slip into holes on the other.  I did this and cast larger items with Delft clay.  If you could devise a frame for which the metal can be poured in from the side of the frame rather than the top or bottom, gravity may assist in moving the molten metal faster before cooling.  Another idea might be to cut a trench rather than a funnel shaped hole for the sprue in the top of the mold, with the trench having several holes entering the mold cavity so you are filling the mold from several locations simultaneously.  In any case, make your model such that the really thin and narrow parts of the side plate are over sized to allow less restricted flow of the metal.  Then file or cut down the excess on the cast plate later.

dave    

[jerrywh]

 Smart dog gives excellent advise. No way to improve on that.

[Hemo]

Jerry, is that gas furnace with a propane tank? Is there a blower attached to it?

I don't see myself at this point pouring multiple parts at once--I'm probably going to stick with one or two single castings as needed for now, so probably don't have to melt large volumes of brass or silver. The big furnace looks intriguing, but I'll bet I could get by with something a lot smaller. I've seen some videos of melting brass for pouring in a fairly small crucible using an acetylene torch applied from above. I could probably melt enough brass for a small part like an escutcheon by this method, not sure if it would be adequate for a sideplate, unless poured as two or three pieces (ala Smart Dog).

Dave, how do you melt your metals?

Gregg

[davec2]

Some previous posts about casting you might want to look over:

http://americanlongrifles.org/forum/index.php?topic=5102.0

[smart dog]

Hi Gregg,
For most castings, I melt the metal with an acetylene and oxygen torch.  You can also do it in your oven using a crucible.  Gregg, give the side plate a try as a single pour.  Make a simple wooden frame and give it a try.  Check out the link below and to see a frame I built scroll down through the comments to near the bottom.

http://americanlongrifles.org/forum/index.php?topic=4843.0

Maybe try the trench idea and cut a lot of gas escape gates all around the mold and particularly at the narrow parts.  Heat a lot of metal beyond what the casting needs so the lump of hot sprue will keep the mold hot.  Have multiple holes into the mold from the trench and pour the molten metal in the full length of the trench.  You can use the excess metal again. Just cut it off the casting, clean off the clay and soot, and then soak it for a few hours in muriatic acid to really clean it.  Then melt it again for the next piece. You also won't waste much clay.  Just scrape off the soot and char and save the rest for reuse.  If it doesn't work at first add more holes or metal and try again. Go for it Gregg!

dave

[jerrywh]

 That cruciple furnace is made out of a 5 gal bucket as you can see. It is lined with castable refractory.
http://www.sheffield-pottery.com/LOUCAST-3000-CASTABLE-MORTAR-p/lvclc.htm

 It has a lid of the same construction with a hole in it for observation and inserting a thermocouple. The only blower needed is a hair drier. and it blows too hard so I devised a butterfly valve to adjust the air flow.
 It runs on propane. The propane is metered into the blower pipe by means of  1/4" copper tube with a simple small valve.  There is one bad feature of this setup. It requires constant attention because if the blower should quit the fire will flame out for lack of oxygen  but the furnace will retain a high heat and flood with propane. at some point thereafter it could explode.  If the blower quits the fuel must be shut off immediately.  I poured hundreds of parts with this small furnace and also did a lot of case hardening years ago.  That big burnout furnace is 8cu.ft. it runs on natural gas. One like that cost as much as $8000.00 years ago. I made it for about $700.00 You can't see the big furnace in the photo.

[Ed Wenger]

Gregg...., take a look at the attached link    http://americanlongrifles.org/forum/index.php?topic=41286.0

Scroll down to the bottom of the page and there's a couple photos of a side plate I cast.  The pattern was done with brass, but obviously, you could use wax or wood.  It was cast in one piece utilizing Petro Bond sand.  I made a cope and drag out of 1" pine, ripped to about 2" or 2 1/2".  As you can see in the photos, vents were utilized on the sides of the pattern.  Another thing that was very effective was a riser at the front end of the pattern.  The sprue  feeds into the center of the mold.

I melted the brass in a burnout oven, only because I don't have a furnace.  Because of the amount of brass that's needed, I'm not sure a torch is the best option for a one piece cast side plate.  At any rate, I was pleased with the outcome, and will definitely use this method again, although I'll probably do the pattern in wood.


           Ed

[Hemo]

Thanks to all for your replies! Great work on that sideplate, Ed! I'm certainly encouraged to dive into this. Need to get some supplies and get to work--I'll post progress pics.

Ed, what size crucible would I need to melt enough brass to do a sideplate like yours?

Gregg

[T*O*F]

, I'm not sure a torch is the best option for a one piece cast side plate

If using a torch to melt brass, one should get a rosebud tip, which will give the high heat required to melt it.  The welding and cutting tips are too concentrated to heat a large mass.

[smart dog]

Hi,
Dave,  I agree completely.  I have a rosebud and boy it does make a difference.

dave

[Ed Wenger]

Gregg,

I used a #4, 6kg crucible, but would probably recommend a #3, 4kg.  I purchased mine through Amazon.  You can also get Petro Bond clay there.  Personally, I've found very little, if any, difference between Petro Bond and Delft clay, and it's much cheaper in quantity.

I would also recommend some casting brass that can be purchased through Rio Grande. 

I also agree with both Dave's that a rosebud tip is preferable when melting brass.  I use one as well when melting smaller quantities of brass such as a thumb piece.  For those I use a hand held crucible and torch or mapp gas.  However, for the larger quantities of brass needed for a side plate, I'd be worried about the zinc loss as Jerry pointed out, hence the furnace or burn out oven to limit O2 exposure.  That's just me, and I have a burn out oven, so that's what I used, but that's a fair amount of brass that your melting....


         Ed

[smart dog]

Hi,
Ed is right about using the oven for larger quantities plus with your programmable oven, you can set the temperature to exactly that best for metal flow.  Ed mentioned casting brass fro Rio Grande.  Just make sure you get the yellow brass, not bronze.  Also, I find best when I reuse brass, to make a 50-50 mix of the used brass and new casting chunks. Again, any old brass should be pickled in muriatic acid before being used to make sure it is really clean.

dave

[Hemo]

Thanks again for your input, gentlemen!
I'll get to work on this.

Gregg

[Smoketown]

Because some of us are true collectors (scroungers).

How good is cartridge brass for casting?

Cheers,
Smoketown

[Goo]

I like to use a thin wire to put pinholes through the top half of the sand mold/clay mold to let gasses out and increase fill ability because gravity pour is does not create a lot of pressure inside the cavity.   My preference is to use vacuum pressure and investment wax burnout casting but that is a big financial commitment for most people.      I taught a class last year at the art center in WPB, Fl on sand casting the premixed product ( which I won't name but it was a dark red)  which we tried was too thick and gummy it would burn and stick to the castings and made cleanup a bit more troublesome.  So I cut the mold product with white play sand to the point where it would still perform and clump with out all the smoke and alot less burned up residue.   You are doing raw science Good luck and don't give up.

[jerrywh]

Smoke town. Cartridge brass is excellent but there is a small problem with melting it.  If you just melt a bunch of cartridges you will end up wit ha lot of slag or burn off a lot of zinc. The bet way to melt it is to slowly add it to a larger mass of melted brass.