Casting a blank with PVC pipe

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J

jimmyz

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Providence Forge VA
I need some help/advice on using a pvc pipe to cast a blank.

The blank has a design carved into it, that I want to "fill" with colored PR and then turn back down. The blank is a little larger than final size, and the carving goes all the way thru to the center hole. I am not using a pressure pot.

I plan to glue the tube in place, mill the ends flush with the tube, put a cork in one end, fill the tube with lead shot, plug the other end, place the blank in the pipe, and fill the piece of pipe with colored PR.

Will the blank come out without too much trouble? Do I have to do anything special to the pipe? Other suggestions?

Thanks for your help!
 
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Hi Jimmy, I cast most of my blanks in 22mm plumbers pipe and they come out just fine. Sometimes I might have one that is a bit tacky and I have to wait a little longer for it to cure before it will come out but not often. Have a look at my previous posts to see my setup.
Eric...
 
Jimmy, if you could provide a couple of pictures, I would greatly appreciate that.

I am very interesting in what you are doing, and would like to know the dimensions of the pipe, the brass tube, the blank you are starting with, etc.

Thanks
 
Could you cap the top of the pipe with a nipple and then add pressure to reduce bubbles? Kind of a one blank pressure pot.

Danny
 
Use silicone plugs for the hole. You don't need to weight the blank down, just use a wire or piece of tape across the top of the pvc to hold the blank down and centered.
Before placing the blank into the pcv, use a brush to work some of the resin into the carving. The resin doesn't need to be catalyzed, since there will be very little resin in the carving. Once the catalyzed resin is pored, it will cause the non-catalyzed resin to cure. By brushing resin into the carving, it reduces surface tension that will assuredly trap air.
This technique is used with under cuts as well. Using a multi-piece sealed mold, vent holes are also used.
 
More4dan said:
1" schedule 40 pvc pipe has a minimum burst of 1440 psi and a recommended working pressure of 270 psi. Not much chance of over pressuring.


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Click to expand...

1" is a waste of resin. 3/4" is better suited and for a recast, and 1/2" would work pretty well for a recast when just filling an engraving.
3/4" pvc is actually stronger than the 1" also, with a burst pressure of 1550psi as opposed to 1425psi for the 1".
The collapse pressure is also significantly higher, not that any of that applies to casting.
 
mckenziedrums said:
I stand corrected... I suppose the trick then would be to come up with a way to cap it off that was easily removed and wouldn't pop out under pressure.
Click to expand...

A threaded plug?:wink:

A spigot would also be required.
 
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mckenziedrums said:
I stand corrected... I suppose the trick then would be to come up with a way to cap it off that was easily removed and wouldn't pop out under pressure.
Click to expand...


Maybe try threaded connectors and possibly install a salvaged bicycle tire valve on one end cap to pressurize it.

This got me thinking, gonna have to do a bit of experimenting here and maybe try making some really long rods to cut into shorter blanks. (one more idea on my stack of ideas I intend to get around to someday).
 
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