rolling block action cast in brass

[dallen]

a buddy of mine ask me if I could cast a remington rolling block in brass and you guessed it I said yes. well anyway casting it in brass and getting a good casting are two dogs of a different color.

I've done this three times with the same problem everytime, doesn't matter what I do. increased the gate size so it would feed, put in a bob and it still has this honking great shrunk area in the side.

I know I'm hot enough the stuff runs like water.

its hard to see but just below where the barrel screws in is a great honking sunkin place. so what am I doing wrong, like use a bigger bob closer to the part???

[HT1]

Your riser is not close enough to the part it's also not tall enough,
The shrinkage in the riser clearly drops below the top of the casting, so you are not getting complete feeding.

if you have no more metal capacity, shortening the gate will help alot,
you might get away with losing the sprue, and pouring straight down the riser, if you go that route, drop the temp of the metal 50-100 degree F

[dallen]

that was my next try, to increase the height of the riser and to also put it closer I have plenty of material so running short isn't a problem. will have to find something to use for the riser mold, Franks cat food can ain't gonna be big enough, have to find something thats two three times as tall.

sounds like tomorrow is going to be a fun day.

thanks HT good to see you made it back from your walk about.

[dallen]

ok bigger riser no shrinkage in the part lots of other problems like forgetting to cut the gate from the sprue to the riser, so when that overflowed I knocked a hole in the shrink bob and poured it that way which caused some problems like sand inclusions but at least I got a better casting not perfect but better.

[Jammer]

I've been following your pictures on Photobucket. Looks like a very good bunch of castings. I don't know what the deal is with Brass, it seems to always cause some problems. Chill blocks and better feed from the riser seems to be what the pro's call for.. ??

[dallen]

Hi Jammer, hope the photos haven't been to boring, not a lot to do since I don't have to get up and go to work or wait for them to call.

anyway HT suggested a bigger riser and to put it closer to the part, which seems to of gotten rid of the shrinkage but I goofed yesterday when I poured the one in the above photo and didn't cut the gate from the spure to the riser,,,,,,ssooooooooooo its not so pretty when its in your hands up close.

anyway I have it molded again but my backs decided to play games with me so I don't know if I will pour today or not can't hardly walk feels like someones shoved a golf ball into one of the joints in my spine, so will just have to see.

David

ok heres the photo from todays pour

[Jammer]

Did I send you any of those little cups? They look like peatmoss but are the exothermic cups. If you cut the bottom off you can use it as a riser or leave the bottom on and make a blind riser. It lights up when hot metal hits it and keeps the riser fluid for a while.

[dallen]

yes you did but I tend to try not to use them as I only have a few and the flask I was using is pretty cramped for space the glass I used worked out pretty good. I also cut the gate from the sprue to the riser this time.

I think that this one is good enough for him to machine, anyway I am not going to pour anymore till he cuts into it and sees if the watermelon is rotten on the inside.

I may mold up and pour me a mortor and pestal out of brass I think it would look pretty cool.

[Jammer]

I'm glad I sent you some, I'm getting a little stingy with them. I only have about 20 left and don't think I'll get anymore free ones. At first they were just too much fun to set fire to them and watch them burn white hot. Able to melt and pour a few ounces of ally without a furnace.

[dallen]

poured the receiver again today, used a new pattern that was made by my friend Doug of SVSeeker in Tulsa, also used different metal for the pour NiBrAl I believe is the abbreviation for it, same metal that Doug has been using for his Prop blades for the sailboat.

Anyway here is a picture of todays pour, it has some pits from what looks like loose sand in the mold (had trouble getting mold to close) (long story)