# Casting small parts in pewter using QuickSil



## Grimm (Oct 5, 2009)

I have learned so much from this site and all the excellent craftspersons, who freely give their insights and knowledge, that I had to give back a little bit. Hopefully this will help those who would like to cast their own parts in the scale of their choosing. I have broken this post up into several parts because I realized that I have taken about 30 or 40 pictures of the process and it's going to take me a bit to describe everything. The first part is making the master for the mold. 

To cast parts you first need something to cast. This is called the master and it is the pattern that you wish to replicate. I wanted to make some of those large cast iron washers that were used in wooden car construction to keep the bolt heads from pulling through the wood. The prototype I wanted to make was about 3 inches in diameter. I'm working in 3/4" scale so I need to divide the prototype diameter by 16 (1:16 scale) to get the scaled diameter of 3/16 inch. The prototype bolt head was about 1/2 inch in diameter which is about 1/32 inch in scale. This is almost exactly how large a 1-72 bolt head is so I will make the hole in the center sized to allow for the correct clearance. The thickness will be about 1/16th of an inch as the prototype was a bit chunky. 


I decided to make the master out of aluminum because I have some 1/4in rod in my stash. You can use other materials if you wish, QuickSil doesn't need much heat or heat up when it cures. I have used copper, styrene plastic, and green-stuff modelling clay to make masters with out problems. QuickSil likes to stick to wood so if you use it, seal it well or coat it with liquid dish soap as a release. 


I cut off a 3" length of the aluminum rod and chucked it up in the lathe:











Here is the aluminum rod in the 3-jaw chuck on my lathe.










Next I faced the end of the rod flat.










Reduce the diameter to 3/16" so it matches the correct scale.











Start the hole with a center drill so it's nice and centered.


















Drill the hole. I drilled it deep enough so I could make two masters for my mold.











Next I changed out my cutting tool out for a parting tool and placed it 1/16 in from the end. I did this now so I wouldn't have to try and get the distance correct after I had rounded the edges of the washer.











I moved the parting tool away from the rod so I had room enough to round the washer with a file. Here is the washer after I rounded it and moved the parting tool back to the rod so it's ready to part the master off. 












Once parted off the tool leaves a nib behind that needs to be removed. I just placed some 150 grit sandpaper down and rubbed the master back and forth until it was gone. You can also adjust the thickness in this way as well to make sure that both masters had matching thickness's. 











Here is one of the masters with a 1-72 bolt in place. To make the second master all I did was to move the parting tool again 1/16 in from the end of the rod and then moved it away. Round the master and then part it off. Clean it up with the sandpaper and match the thickness to the first one. 











And here they both are, next to the 1-72 bolt. 


Next is making the mold...

Jason


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## Grimm (Oct 5, 2009)

On to building the mold. Lets start out with a picture of some of the tools and items I use to make the mold:










In the picture, left to right, I have a cast iron ladle and hot plate to melt the pewter, the two QuickSil parts that you mix to make the rubber molding compound, modelling clay, pewter, bag of unscented talcum powder, C-clamps (too small), wooden mold frames, dowels for sprue's, etc., and two metal plates to cap the mold frames.


QuickSil, although expensive, has a lot of positives. It's not toxic, doesn't smell, easy to mix (50/50), can withstand 800 F, hardens quickly (15 to 25 min.), the molds can be used 100's of time (probably more), and the molds made from it are flexible (kind of like tire rubber). I just checked on line and it goes for about $50 for a two pound kit that could last you for about 20 molds or so depending on size.










First I place one of the metal plates down and put one of the frames on top of it. The frames I just slapped together and wrapped them with wire so they couldn't pull apart. If your frame comes apart I can guarantee that the QuickSil will pull away from the master and you will have a bad mold.











I then fill the frame with modelling clay, this gives us a place to put the masters on and sprue's. 











For this mold I wanted to place a sprue first as it needs to be a large one. The reason for the large sprue is because I don't have a mold spinner to force the metal into the mold. I have to rely on gravity and with the parts as small as they are, I need all the help I can get. The large volume of the sprue puts some weight on the channels in the mold and helps force the metal into the small parts. It also helps with shrinkage as the metal will contract more in the large sprue instead of the small parts. I try and keep the clay flat around the objects I'm embedding into the clay. To help with that I use a clay modelling tool that works very well.











This picture came out fuzzy, but it shows the placement of the masters in relation to the large sprue.











Next I took a dowel and put in several indentations into the clay around the periphery of the mold frame. These act as registration marks so the two half's of the mold will line up and not miss-register.











Now I place the other mold frame on top of the other that will become one half of the mold. I didn't need all of the space in the mold frame so I filled part of it with clay.











Measure out equal amounts of both parts of the QuickSil. These are too big so I wasted some of it, but it's much better to have too much then not enough. Mix them together, but don't take more than 1 or 2 min. to do it. Fill the remaining space in the mold frame to above the top. You want the QuickSil to be under pressure in the mold, otherwise it will not turn out. If some squeezes out when you clamp it, it's no problem. 











Here is a picture of how I clamp the mold once I have filled it with QuickSil. It's better to use two clamps, I also used my vice but I don't have a picture of that. Now go get a cup of joe, beer, etc and wait. I like to wait for about an hour, but if you are impatient 30 min. is fine. The colder it is the longer it will take to cure.











Here is what it looks like once it's cured. 











I clean up the mold and then fill the bottom again with clay. Try to get it as clean as you can, especially around the master. I then coat the mold with liquid dish soap (not the clay), this acts as a release, QuickSil likes to stick to itself very strongly. Again fill the remaining space with another batch of QuickSil and clamp it.











This is what it looks like once the second half of the mold has cured. 











And this is the mold after I have cleaned and trimmed it. I used a Exacto knife to trim the flashing and clean up the sides a bit. 











Using the same knife I carefully cut the sprue's and vent holes to each of the masters. I also cut out a fill hole to the large sprue to pour the metal into. The vent holes are very important especially with small parts like this. This allows air to escape and not sit in the mold, messing up your cast. If you keep getting a bad cast, adding additional vents can help the molten metal get to the problem spots.


Next installment will be about casting the parts.









Jason


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## spincaster (Mar 10, 2012)

Jason, 

Interesting post. I do spin-casting professionally and use RTV mold cavities for fragile or complex patterns where parting line needs to be accurately positioned. I recently bought what I think is quick-sil under Contenti's label but haven't had a chance to try it yet. I prefer liquid RTV but the quick cure time of this material is what attracted me. My main concern is that cure may be effected by other materials. I'm also wondering if the surface finish on cast parts is similar to standard RTV. 

Jack


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## Torby (Jan 2, 2008)

Interesting. Thanks for [email protected] url(http://www.mylargescale.com/Providers/HtmlEditorProviders/CEHtmlEditorProvider/Load.ashx?type=style&file=SyntaxHighlighter.css);@import url(/providers/htmleditorproviders/cehtmleditorprovider/dnngeneral.css);


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## Grimm (Oct 5, 2009)

@import url(http://www.mylargescale.com/Provide...ad.ashx?type=style&file=SyntaxHighlighter.css);@import url(data:text/css,);@import url(/providers/htmleditorproviders/cehtmleditorprovider/dnngeneral.css); Posted By spincaster on 15 May 2012 04:46 AM 
Jason, 

Interesting post. I do spin-casting professionally and use RTV mold cavities for fragile or complex patterns where parting line needs to be accurately positioned. I recently bought what I think is quick-sil under Contenti's label but haven't had a chance to try it yet. I prefer liquid RTV but the quick cure time of this material is what attracted me. My main concern is that cure may be effected by other materials. I'm also wondering if the surface finish on cast parts is similar to standard RTV. 

Jack 
As far as I know, the only thing that affects the cure is sulfur based clays. I would assume that anything with sulfur in it would affect it too, but I don't know. I have never used RTV rubber so I'm not sure how well it would compare to QuickSil. On the mold you can see the sanding marks from when I sanded off the nubs. I think it does pretty well in preserving the fine details, just make sure you have some pressure on it while it cures.

Jason


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## spincaster (Mar 10, 2012)

Jason, 

Actually what you are using IS RTV (room temperature vulcanizing) Inhabition to cure from sulphur is typical of addition cure RTV but some addition cure RTV is very sensitive to all sorts of things like paints. I frequently use 3D printed patterns and am hoping that quick-sil cure isn't inhibited by the pattern materials or chemicals used to clean/wash the patterns. Typically I just need to cast a few parts to use as production patterns to make a vulcanized mold. 

Jack


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## Rods UP 9000 (Jan 7, 2008)

Thanks for showing your way of doing this Jason 
I will be trying some of this as I'm setting up to do resin casting along with the white metal that I do now. I have everything but the RTV and resin. 
The pressure- vacuum pot is big enough for a complete 20.3 passenger car sides to fit in. 

I know that when I vulcanize organic and then go to a silicone, I have to clean my mold ring and plates with Acetone because of the sulphur. 
Also super glue as the same effect on silicone. I use the "new" low temp vulcanizing silicone when the master is plastic or other low low melting substance. 


Rodney


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## Grimm (Oct 5, 2009)

Thanks guys, that makes sense. I haven't painted any of my masters so I don't know how QuickSil would handle it, or not. I have constructed masters with super glue and it did not appear to affect the cure when I molded them. 

When I first started this I wanted to be able to cast parts without having to have a lot of tools and whatnot. This method has worked out and isn't too expensive to get started in. The most expensive items have been the QuickSil and the pewter.  All together I think I have spent less then $80 for everything. It's probably a bit more now that metal prices are rising so fast.  

Jason


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## GaryR (Feb 6, 2010)

Most sites like Smooth-on use the label " tin " cure, and the " addition " cure will appear in the text somewhere. They mean the same thing for our purposes. The other kind is " platinum " cure. It doesn't have the temperature tolerance of the tin cure. Oh, and the 1 to 1 rapid Micro Mark sells is tin cure. The side frames of all of my trucks are made this way. My 2 ¢ 

GaryR


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## Grimm (Oct 5, 2009)

Thanks Gary, I don't see any cure type label on the QuickSil jars. I did check their web site and it looks like I got the temperature wrong, QuickSil is good to up 650 F. The lead free pewter I'm using melts at 460F so still good.









On to the casting part...










The first thing to do is clean the mold and remove the remains of the clay and dish soap. Dry the mold thoroughly, water and molten metal do not mix and would make you very unhappy if any got on you. Once the mold is dry (and I mean really dry), dust the mold with the talcum powder. Don't use the scented powder, it will interfere with the cast. The talcum helps the air move out of the mold and keeps air bubbles from forming. I like to use one of my wife's old makeup brush to apply the talcum. 











This is the tricky step. I use the same metal plates I used before and clamp the mold between them with a C-clamp. The trick is that you do not want to squeeze the mold too much because it will distort the cast. I like to get the clamp just tight enough so that it will stay suspended around the mold and not fall off. You don't want it too loose either, then you will get lots of flashing or the metal will simply leak out. There is a middle point some where there.











Now hopefully you have the metal all hot and melted in the ladle and pour it in. I poured too much and it spilled over, so do it in a safe place where the molten metal will not hurt you or anything else. 










As luck would have it, the first cast is a good one. Both washers are complete and no air holes.


















Now you can cast as many as you need, and if you need more, the molds are right there so you can cast them up. I cut off the parts with a pair of wire cutters, you can get fairly close to the part and trim off the sprue's and vent projections. 










Here is one of the washers cleaned up and installed on a wood beam to show you how they will look once on the model. 











And here is what the originals looked like. 

Happy casting!

Jason


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## Robert (Jan 2, 2008)

Like everyone else I found this interesting and informative. Thanks Jason.


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## bnsfconductor (Jan 3, 2008)

Do you need a electric hot plate to heat up the pewter? Or could you use a gas camping stove? This looks like an interesting project, and easy to do. I've got some frogs, and point work that I want to cast up in metal. 
Is pewter strong enough to hold up for turnouts? Or should I look for something else? 

Craig


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## Rods UP 9000 (Jan 7, 2008)

Jason 
Thanks for showing us your work 
Those came out as good as if it was done on a spincaster. I'm going to try this to make some submasters and see how well it works. 


Craig 
The Tin based metal is too soft but here is a link to some that I think will hold up for what you want. 

http://www.rotometals.com/ProductDetails.asp?ProductCode=Zamak+3+Ingots&CartID=1 

I haven't tried any yet but want to soon. It has a melt temp of about 775 degrees and guessing cast temp would be around 800 deg for what you want to do. One thing to remember is as the melt temp goes up the mold life goes down. 

Yes a camp stove will work to melt the metal. The Zemak will take awhile to melt though. 

Rodney


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## spincaster (Mar 10, 2012)

Posted By GaryR on 15 May 2012 07:58 PM 
Most sites like Smooth-on use the label " tin " cure, and the " addition " cure will appear in the text somewhere. They mean the same thing for our purposes. The other kind is " platinum " cure. It doesn't have the temperature tolerance of the tin cure. Oh, and the 1 to 1 rapid Micro Mark sells is tin cure. The side frames of all of my trucks are made this way. My 2 ¢ 

GaryR 



Addition cure is sometimes called "platinum cure" and condensation cure is sometimes called "tin cure". They are the two basic types of RTV rubber. I use condensation cure RTV because it is less problematic than addition cure can be. Addition cure rubber has almost no shrink. Condensation cure rubber has about .9% shrink. Both are generally good to 600DegF. Those containing a heat resistant filler like iron oxide (red in color) have a little more head resistance 650DegF and are a little harder durometer and thus better for casting pewter. 

For hobbyists and cheapskates like me, Dow Corning 3120 with type S catylist, is a great RTV though sometimes hard to find. It is a condensation cure rubber. The nice thing is that the catylist is in paste form and is easy to measure for pouring small molds. You can also adjust the amount of catylist to control the cure time. I have tried others and always come back to this one. 

The Quicksil interests me since I might be able to go from fragile pattern to production mold in one day or less.


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## spincaster (Mar 10, 2012)

Jason, 

Next time you make a mold you might want to put your gate a little to the side and put your vent at the top of the part. Metal is going to fill from the bottom up so once it gets up to the vent it isn't venting. 

Casting temperature for lead free Britannia (pewter) is usually about 550F - 600F for small parts. Depending on what I am casting I vary temperature from about 525F-800F. Above 650F is extreme and probably NOT something you want to try. 

I'm looking forward to trying Quicksil 

Good project and nice that you show others! 

Jack


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## Rods UP 9000 (Jan 7, 2008)

Jack 

Have you tried to cast anything with Zemak?? With the price of Britt metal now (around $1700 for100 pounds the last time I bought some) I want to try it for the big stuff like truck sideframes, airtanks and stoves (20.3 scale) and use the Britt for the small stuff. 

Rodney


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## spincaster (Mar 10, 2012)

Rodney, 

Brit is down a bit right now but haven't gotten a quote lately. I am guessing about $12/lb right now. I usually buy 40# or 60# box and the price isn't too bad. I normally cast 92/8 alloy 

I find that zinc aluminum is a nasty alloy to cast. I have what is called ZA1 which is supposed to be good for small parts. I purchased it for specific parts which didn't work out. Some molds are toast after only 20-30 shots and others last a long time. Very unpredictable! I did one job using tapered brass cores that worked well but it was kind of a nightmere to do in July. Casting temp is about 780F which is just hot enough that you really need to be very careful. Mold material needs to be specific to ZA. I bought a melt pot and ZA and wish I hadn't as it sits mostly unused in the garage. I have been told that you have to keep ZA separated from Brit to prevent contamination. 

Wana buy a digital melt pot and some ZA? 

Jack


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## Rods UP 9000 (Jan 7, 2008)

Jack 
I sent you a message 
Rodney


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## GaryR (Feb 6, 2010)

Got some of the platinum cure silicone. I knew you could use scraps of an old mold to use as filler in a new mold. I suspected you couldn't mix tin cure scraps with a new platinum cure mold.....I was right, they don't mix at all !! Tin with tin , and platinum with platinum only! 

GaryR


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## Semper Vaporo (Jan 2, 2008)

Question:
Why aren't the vent holes in the form of a "J" off the bottom of the part with the top just above the top of the part. Liquid seeks its own level so when pouring the part would be filled when liquid comes out the top of the "J".

Something like the following markup of a part of your "Casting24.jpg" photo:










The "Red" being the vent channels.


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## Grimm (Oct 5, 2009)

Jack, Semper,

Sorry I haven't responded sooner, my youngest son graduated high school and is moving out to his own apartment, all in one week no less. The kid has never done anything half way.









On the vents, I haven't noticed any difference to how I position them or what direction they go. Just as long as there is some space for the air bubble to move to it works. Maybe the difference is in doing a spin cast and how I am doing it with a gravity cast? I have a feeling that most of the venting is handled with the talcum powder anyway and that you only need to add vents for the problem areas. Most problem areas I have found is in tight corners, very thin parts, and in under cuts. I even have used a sharp drill bit in a pin vise to drill holes in the mold for those areas. Anything to move the air bubble out.


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