Silicon Bronze Castings

I am in the process of having some parts cast in Silicon Bronze, (873 Everdur). My question is how difficult is this cast material to machine, I need to drill & tap holes & machine the inside of my cast part.

 

It can be a little gummy sometimes on the mill or lathe, but everdur really is some nice stuff to work with. It tig welds like magical butter!
Drilling and tapping is easy peasy.

 

Thanks, I have a few holes to bore & counterbore. A few very fine threaded holes 5/8-24, 3/4-24, & 3/8-32. I am building a small valve body. The tensle strength is supposed be around 55,000 so I should be good.

 

So it's been 6 weeks since I sent my 6 polycast 3D printed patterns to the foundry. I just found out that my castings did not turn out. Lots of porosity & mouse bites. It took about 6hrs. to print each pattern & 2hrs. to sand & polish them. The foundry made the gates. They said the printed wax melted & burned-out real clean. My parts are valve bodies that need to be free of porosity so they won't leak. I actually had better results with the ones I sand casted last fall. I purchased a box of R&R casting plaster, a vacuum pump and a muffle kiln. So now I plan on trying it myself.

 

Good! You can't do any worse! Sucks about the lost time, I just hope they didn't charge you.

 

They wanted to weld them up, and charge me labor for there time. Not sure if they have a new plan or not? It would seem like a simple part to cast to me.

 

Valve bodies are more traditionally done with gunmetal bronze/red brass/leaded gunmetal due to it's sound, pressure tight castings, corrosion resistance and good machinability.

 

I'm not going to say my castings I pour in my driveway don't come out with some imperfections. But they have always come out better than THAT! If they only had one pattern to work with, you get what you get. Now if the casting has to be high quality like what sounds like you need, then they should have made a mold and cast that sucker until they got a good one. If you gave them one lamb to slaughter, then it's on you to pony up the cash to complete the job. That thing is SOLID, that's an easy part to cast, ya just gotta have runners and sprues larger than the part so they cool last. THEN and this is where I think they screwed up, pour it at the bottom end of the temp range. I have zero experience with anything other than wax, which is what I would have made that part out of. You had the 3d print, that was the time to make a silicone mold and pour a few waxes for them. Not everyone is up to speed on this new fandangled stuff. (showing my age here) I'm not seeing shell failure, but temperature or leftover crap inside from burnout is what created those holes.

Keep at it until you get a solid one and might even have to saw cut one in half to check the inside. You using an art foundry????

 

I gave them 6 patterns, they tried one first. They said the first one was good. I saw porosity in that one also. I think they are more setup to make art projects.

 

Yes, I think the foundry is more geared up to do art projects.

 

Did they burn through all 6 yet?

 

Yes, but I made more of them. I wanted to print the spurs & runners with the pattern but they just wanted to hang them on with wax.

 

I'd be tempted to split the CAD in half and add holes for pins and extracting screws, print it with a couple more outer layers, coat it with some epoxy and/or paint, and try it as a straight-up sand casting. You could do a small match plate and have all of you gating pre-arranged.

 

That's exactly how I did the original sand casting. I just wanted to get a smoother surface, so I opted for lost wax. I haven't really been very good at sand castings my sand always falls apart before I get to pour. I have tried several green sand recipes and purchased premixed sand.

 

Petrobond isn't smooth enough for you??? Amazon has 190mesh, that's pretty fine! https://www.amazon.com/Teton-Bond-P...d=1684213018&sprefix=petrobond,aps,129&sr=8-1

I'd be happy to take a poke at lost wax for you, but I'm in no position to cast anything right now unless it's concrete! I'd fire that foundry and ram it up in p-bond. Or hit up HT1 in Jacksonville, I bet he'd do a stellar job and cheaper than that art foundry.

 

I actually purchased some petrobond & didn't try using it. Can I pack this around my pattern & then use green sand to fill in the rest of the box? I furnished the patterns. The art foundry charges $22@lb. for the finished cast part + $33@hr. to setup the gates & sprues. I haven't received a bill yet?? I don't have any good castings either. Should I jump ship with this guy?

 

One other question,
Where can I purchase a chunk of refractory brick to replace a broken pc. In my muffle kiln. The finished pc. needs to be 1-3/8" x 3" x 12". I can cut it down if I could find a larger pc. to start with. I've searched high & low & can't find anything??? I wish I could actually find a pc. 12x12 so it wouldn't be a 2 pc. oven top. Needs to withstand 2000 f.

 

I'd figure out some way to stop work and cash out with him so as not to sour things to where you can't work with him in the future, like 100$ and end up with the best 1 or 2 castings or something.

I like Smith Sharpe in Minneapolis for refractory stuff and nearby Sterling Supply for graded sand (they sell into the media blasting market).
https://ssfbs.com/
I am working (OK learning to work with...) with Kast-o-Lite 30i Plus lately, not the cheapest solution but you could make a mold and cast a one piece top good to 3000F. They make lower temp versions as well.

I have done a thing where I put 2x4 sleepers into 1x4 flasks halves to take up room to conserve Petrobond. After doing that a couple times I just bought another bag.

Did you read about the June casting/machining event in Tamarack, MN? Your project seems like a good fit, might be worth messaging Daryl (Uglydog on the forum) about it.
https://forums.thehomefoundry.org/i...vents-in-tamarack-minnesota-summer-2023.2498/

 

Thanks, I'm checking into this now.