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#1
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What to use to make a mold?
I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if mold material can withstand 500 degrees Fahrenheit so I can pour lead into it and then cover it by fiberglass. Alternatively I would use the mold to create a fiberglass container first and fill it up with lead pellets. So my question is what do I use to make a mold, gypsum if so what kind, anything else? Andrzej |
#2
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What to use to make a mold?
On Mar 22, 5:23*pm, AK wrote:
I want to make a small mold I would later use to create a fiberglass container to hold lead weight. It would be nice if *mold material can withstand 500 degrees Fahrenheit so I can pour lead into it and then cover it by fiberglass. Alternatively I would use the mold to create a fiberglass container first and fill it up with lead pellets. So my question is what do I use to make a mold, gypsum if so what kind, anything else? Andrzej High temp RTV rubber can withstand up to 1000deg F. It's not cheap stuff, but it will work quite nicely... If you use gypsum or plaster products, just make two molds, (after your first mold is made make a male model from it to cast new females off of...) as it would be difficult to get out your lead w/out breaking it, assuming it survives the thermal shock of the pour. Heat up your plaster mold in an oven to within 100deg of your pour first to avoid that pitfall, but you must very slowly heat the plaster up since it may have micro water in pores that will superheat and make it crack as the steam exits. Take at least 4 hrs to bring your mold up to temp (after 24 hrs minimum cure) , ramping up 100deg/hr until at 400ish... plaster is cheap and easy to work with, so it will probably be most practical. note-plaster expands 1-3% when cured, so take this into account for allowances if you have critical tolerances. If you need precision plaster/gypsum there is a product called Ultracal (in 30 or 60 minute cure versions) made by US gypsum that does not expand or shrink. it's cheap enough to use too at like $30/50# . It feels and mixes just like plaster of paris but is gypsum based so it cures like cement. Phenomenal product actually... There's always the option to just trap your lead shot in epoxy thickened with cabosil or microballoons etc, which seems much easier but will obviously not provide the same density as a solid block... -Paul |
#3
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What to use to make a mold?
sisu1a wrote:
There's always the option to just trap your lead shot in epoxy thickened with cabosil or microballoons etc, which seems much easier but will obviously not provide the same density as a solid block... It does avoid the breathing of lead vapors, something even a pilot should avoid. -- Eric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * "Transponders in Sailplanes" http://tinyurl.com/y739x4 * Sections on Mode S, TPAS, ADS-B, Flarm, more * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#4
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What to use to make a mold?
On 23 Mar, 02:01, Eric Greenwell wrote:
sisu1a wrote: It does avoid the breathing of lead vapors, something even a pilot should avoid. Is the sublimation rate of lead at room temperature significant? Church roofs seem remarkably resistant to evaporation after hundreds of years, as do the 120 year old lead water pipes in my house. Ian |
#5
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What to use to make a mold?
For a single pour mold, you can even carve it out of wood, like a 2 by 4.
It will smoke, burn the wood (you can blow out the fire), but it will hold up for a single lead weight making. How heavy a weight are you trying to make? And about how big? You could then make the glass cup from the lead part, or even from a block of foam that you cut to about the same shape. A friend once got in trouble with his wife by using one of her frying pans to make lead disks for putting in the seat pan of our old club two place! One thing to watch out for (may not be this way with the gypsm stuff that Paul mentioned), but anything that used water in its making, can trap water inside. Put molten lead in it, and it can be a bad thing. Happy slug making! Steve Leonard |
#6
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What to use to make a mold?
At 02:30 23 March 2009, Steve Leonard wrote:
For a single pour mold, you can even carve it out of wood, like a 2 by 4. It will smoke, burn the wood (you can blow out the fire), but it will hold up for a single lead weight making. How heavy a weight are you trying to make? And about how big? You could then make the glass cup from the lead part, or even from a block of foam that you cut to about the same shape. A friend once got in trouble with his wife by using one of her frying pans to make lead disks for putting in the seat pan of our old club two place! One thing to watch out for (may not be this way with the gypsm stuff that Paul mentioned), but anything that used water in its making, can trap water inside. Put molten lead in it, and it can be a bad thing. Happy slug making! Steve Leonard Lead has a melting temp of about 500 degrees C commercial moulds for casting batches are usually cast iron as are some pans. If you make a mould using sheet steel this would then encapsulate the lead after pouring and prevent the soft lead from deforming under pressure from the fastening bolts. |
#7
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What to use to make a mold?
On 23 Mar, 07:45, Ian Burgin wrote:
Lead has a melting temp of about 500 degrees C ... It might be worth thinking about using plumber's solder instead. It's a lead-tin eutectic alloy, which means it melts at a significantly lower temperature (183 degrees C), but still has a high density (84% that of lead). Ian |
#8
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What to use to make a mold?
On Mar 24, 12:24*pm, The Real Doctor
wrote: On 23 Mar, 07:45, Ian Burgin wrote: Lead has a melting temp of about 500 degrees C ... It might be worth thinking about using plumber's solder instead. It's a lead-tin eutectic alloy, which means it melts at a significantly lower temperature (183 degrees C), but still has a high density (84% that of lead). Ian Do you know of good source for this alloy (I don't know if I want to go to Radio Shack to buy 40 lb of solder? My wallet would be way too light and then I would have to buy even more of the alloy. |
#9
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What to use to make a mold?
On 24 Mar, 23:20, AK wrote:
On Mar 24, 12:24*pm, The Real Doctor wrote: It might be worth thinking about using plumber's solder instead. It's a lead-tin eutectic alloy, which means it melts at a significantly lower temperature (183 degrees C), but still has a high density (84% that of lead). Do you know of good source for this alloy (I don't know if I want to go to Radio Shack to buy 40 lb of solder? My wallet would be way too light and then I would have to buy even more of the alloy. Builders' merchants used to sell it by the kilogram, but it's banned or about to be banned for domestic use so may be harder to find in the UK now. Dunno about where you are. Ian |
#10
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What to use to make a mold?
On Mar 22, 5:23*pm, AK wrote:
I want to make a small mold I would later use to create a fiberglass container to hold lead weight. It would be nice if *mold material can withstand 500 degrees Fahrenheit so I can pour lead into it and then cover it by fiberglass. Alternatively I would use the mold to create a fiberglass container first and fill it up with lead pellets. So my question is what do I use to make a mold, gypsum if so what kind, anything else? Andrzej sand |
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