looking for petrobond, new here

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Harry
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Re: looking for petrobond, new here

Post by Harry »

John, that tablet I sent you is for aluminum only. Look at the BCS site to see their tool, basically a piece of 1/4" pipe welded on the end of a piece of rebar. Roll up some of that tablet (crushed) in foil and stuff it into the pipe nipple, swirl it around in the bottom of the melt. Be sure to keep your head upwind.

Delft clay, I think it is something like petrobond without the sand, maybe some kind of super fine filler. I mixed some up with parting dust and was impressed but never put much time into it. I could see it getting into some even finer detail than even my sand can pick up and hold sharp fins of detail better. Some day I will try some more mixes of high petrobond content mixes with no sand, maybe use plumbago in it for filler. I think something like delft clay would be great for doing small detailed castings that sand wont hold all of the detail in, it is often used in jewelry casting.

Bentone is a modified form of bentonite. Bentonite is used in greensand and absorbs water. When it is altered to become bentone it absorbs oil and becomes the binding agent in petrobond sand. The catalyst is to gel the oil in the mix, supposedly with petrobond II the catalyst is not needed but I have read and heard from a couple of people that they still use the catalyst.
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johncur
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Re: looking for petrobond, new here

Post by johncur »

So now I have a little riddle with 1/4" hardware cloth, flasks are ready. I made one more flask that hinges open so I can get the mold out and ram the next for multiple pours. Not sure if this is standard practice but I'll try it. Can you pour into the sand without the flask being there?
I understand the degassing wand a little but I'm not going to degass the brass, if it were aluminum I would.
My metalwork friend with the forge for melting is back home from a vacation, so we are eager and ready. We may get to it this week so I'll report back.

Is it easy to post pics here? I see there is an IMG tab on the reply screen here but it just puts "IMG" in the post.
Do I need to put a link to a photo site in there or is there a way to just put a picture? Well, I'll go to the FAQs again and try to figure it out.

More later
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Nudge
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Re: looking for petrobond, new here

Post by Nudge »

Can you pour into the sand without the flask being there?
A bit fat NO :o you need to put it back around the sand before you pour other wise the sand will break apart, lift, spill, piss out, burn things, etc. the idea with a split flask is that you can mould up lots of parts with one box (one flask takes up less room than 5 or 6).

I use photobucket for the pics I post, there are a few ways to post them. It would be best to look at the FAQ's as I'm not the best for that sort of thing.
I like to build "Stuff" using Stuff that costs Stuff All!
dallen
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Re: looking for petrobond, new here

Post by dallen »

I use Photobucket as Nudge mentioned. There are lots of sites that will allow you to store a copy of your pictures online, photobucket is just one of these.

to post a photo in one of your messages the easiest way is open up a new window in your browser and to go to your photobucket account. Find the photo that you want to have in the message, place your mouse pointer on it, there will be a menu window that will open up which will give you four different options the last one is img code link, place your mouse pointer on top of the line of code and left click it one time, it will pop up and say copied.
Go back to the browser window that has Found Dreaming open in it, simply click the right mouse key in the menu that pops up select and press Paste, or press Ctrl-V on the keyboard to insert the line of code that will link your photo to the message when you post the message.

If you have questions simply ask if you can't find the answer in the FAQ's
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Harry
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Re: looking for petrobond, new here

Post by Harry »

The best way to post pictues in this forum is to simply upload them into your post. Look right below the posting box (where you type) and you will see two tabs that are labeled 'Options' and 'Upload Attachments'. Click on upload attachments then the 'Browse button which will open a window to find the picture on your computer. Once you select the picture click the 'Add the file' button and in a few seconds it will refresh the page and show the uploaded attachment just below the posting window with an option below it to place it inline, clicking that will put the link to it where ever the typing cursor is.

I say this is the best way to upload here in this forum because pictures become part of the forum then and not dependent on some other hosting service. I remember way back when a couple of hosting services went belly up and any pictures hosted on them just broke. Sometimes when the current services are too busy you will get broken images and who knows what the future will hold as far as them deciding to charge for the services. If the pictures are part of the forum then as long as the forum lives the pictures will too.
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HT1
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Re: looking for petrobond, new here

Post by HT1 »

Nudge wrote:
Can you pour into the sand without the flask being there?
A bit fat NO :o you need to put it back around the sand before you pour other wise the sand will break apart, lift, spill, piss out, burn things, etc. the idea with a split flask is that you can mould up lots of parts with one box (one flask takes up less room than 5 or 6).

Professionally, snak flasks are replaced with a jacket for pouring http://www.hinesflask.com/prod11.htm it requires the snap flask to be built as Isosceles trapezoid, so the jacket can slip on and tighten. Way beyond my carpentry ability. jackets compared to the flasks are very inexpensive, so they are atractive to foundries.

some people will pour molds without the flask in place, and even get away with it if their sand is excellent, and they have a very large amount of sabnd surrounding the pattern, at least 3 inches for a small part, but it is still an unsafe practice. build more flasks
johncur
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Re: looking for petrobond, new here

Post by johncur »

OK, I'll have something around the sand. Sounds too cumbersome to move my hinged flask from one sand to the next when we're pouring so I'll make more. Right now it's little 4-5" square wooden flasks so no big deal, easier than making the fancy snap on jacket. I only need 2 of this first part but will probably do extras to test all these ideas and variables.

I was browsing that Navy manual on here and I saw something good about where to put the sprue. I think it was to put it near the heavier side of the piece 'cause that's where the most shrinkage is? I'll go back and check that out. Also, my friend Morrie the caster mentioned something about sticking a coat hanger into the sand from the pattern cavity to make a place for gasses to go? I think that's what he meant. Boy, sure is a lot to test out on these first few pours.

Was hoping to try it all this week but it's gotten pretty busy and a blown head gasket has complicated every thing. That should be done soon though I hope. I don't know if you've all ever looked under the hood of a Subaru but head gasket (s) are no picnic. Cylinders are sideways, like all the way sideways, horizontal !

Sounds like I can figure out the picture posting, thanks for the help there, and I'll post some stuff. Maybe helpful for other beginners.

Thanks all.
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Harry
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Re: looking for petrobond, new here

Post by Harry »

Venting is not usually needed with petrobond John. When using greensand it is important because the water flashing to steam expands 1700 times in volume. If you do decide to vent poke the rod in while the pattern is still in the mold. Go in from the top of the cope until the wire hits the pattern.
I'd rather laugh with the sinners than cry with the saints the sinners are much more fun...
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johncur
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Re: looking for petrobond, new here

Post by johncur »

OK, We have done our first pours and I'm really pleased with what we've learned. We don't know why it worked like this but I got the part I needed and we've learned enough to keep going. Of course to you pros here this doesn't look so good but I've been wanting to try this for years and finally have.

This shot shows the original and the three pours (not including the one where I forgot to take the original pattern out of the flask ! ) the part is about 2" high x 1/2" thick.
the original and the 3 pours
the original and the 3 pours
The original part was stamped from thin brass sheet so I thickened it up with wax on the back. The first two pours were encouraging but not good. Somehow the third was respectable. I think we made a bigger gate on the third, and placed it and the sprue at the less massive end of the part. The first two had the sprue and gate at the heavier end of the part.

Here are pics of the results:
problems
problems
problems
problems
problems
problems
back of final good one
back of final good one
front final good one
front final good one


We don't know why the third worked OK. Maybe it was the sprue and gate at the thin end. We melted scraps of free machining brass for the pours, used quite a lot of borax flux, and on the third one we skimmed slag off the top of the melt. I don't think we skimmed the first two off. We used a ladle type crucible heated in a gas forge.

Any tips would be welcome, I'll try to get pics of our simple tools posted but they are in my friend's camera.

The sand was very good to work with. We could make the molds quickly but didn't really know how to do the sprues and gates.

On the side, I have a cast brass clock that I knew was made by my grandmother's father who had a foundry in Chicago. My cousin has been doing family research and just recently found out that it was quite a big operation doing industrial work. JJ Hayes foundry, and they even got on the bandwagon to make memorabilia items for the 1893 Columbia Exposition there, paper weights and coins and stuff.

Thanks to all for your help
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Harry
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Re: looking for petrobond, new here

Post by Harry »

John, those results are very encouraging for someone new to casting. I certainly would not consider myself any kind of pro but we do have one or two that stop in here from time to time. I think of where I am at as an apprentice working on his way to journeyman and hopefully before I get too old to do this any longer I will be a craftsman.

I will toss a couple of thoughts out to you though. From the looks of your pictures I would say heat... if the metal was too hot you could end up with other problems but it looks to me that the metal is cooling too fast in the mold and giving the unfilled pieces.

The other thing is a little on gating/feeding of the part. For a small part like this the sprue is the thickest section and it is also the last metal into the mold so it is the hottest so no need for a bob as the sprue will serve but it has to be able to keep that hot metal connection open to the part until the part solidifies. What I do is cut the gate very large right up to the part, within an 1/8" or so then neck it down right there. To my way of thinking the gate is actually just that plane where the runner intersects the part so technically that would be a big thick runner feeding a small gate. The sand I sent you is very nice for cutting gates like this, cut out from the part first with the smaller size then pull away from the part as you cut the runner being careful not to push the sand towards the part.

Unrelated thoughts, on the topic of skimming. With brass the temperature is way above the point of zinc burning off which is why you need to have a cover on the melt. The cover prevents oxygen from getting to the metal and no oxygen no burning. I have done very little brass but when I did I used some hard wood chunks to make a charcoal cover. It is surprising how long the charcoal will last considering the temperature. I made what I called a third hand tong for my crucible that held back the top of the melt so skimming was not needed because the metal came out of the crucible from under the skimmer.

So toss some heat to it and give it another go, soon you will not only your part but a whole new world of things you can make.
I'd rather laugh with the sinners than cry with the saints the sinners are much more fun...
Muller
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