Bronze Casting at home

[Falcon1]

Hello all,

I thought I'd start a thread to show some of my beginning efforts at bronze casting. So far there have been a few successes and a few failures, which is fine since one learns from both (hopefully.)

I took my second six-week bronze casting class last month. Last year, I made a mast gate for the boat I'm building and a nifty jam cleat.
The class mainly deals with the lost wax process which is great, but time-consuming. Once you have your form made in wax, and sprued and gated, you have to dip it in ceramic slurry 8 or 9 times, letting it dry completely between dips.

This year, the instructor (who does teach a short workshop at the Apprenticeshop, as well as at RISD) decided to show us sand casting on the first night, using a small electric furnace. A few of us came the next week with sand casting molds made and patterns to work with, and we were able to pour that very night!

So, from that class, I made two bronze oarlocks using the two-part sand mold, and a solid corgi for my son using the lost wax process.

[IMG]IMG_0822 by Michael Owen, on Flickr[/IMG]

After the class ended, I bit the bullet and purchased a furnace. It wasn't cheap (around $600) but I hope to get a lot of use out of it.
This past Saturday, I fired it up for the first time. I was a little nervous, since it does get up as high as 2000 degrees F., but I was careful and had an extinguisher nearby. Here are some photos.

The furnace. It's bigger than a breadbox, but not by much. Here it is at 77 degrees.
[IMG]IMG_0836 by Michael Owen, on Flickr[/IMG]

The tongs for lifting the crucible out and some leftover gating to feed into the furnace. I also bought some bronze shot, which will be my main metal source. It's silicon bronze.

[IMG]IMG_0837 by Michael Owen, on Flickr[/IMG]

My home-made ingot mold for catching the leftover metal after pouring. So tiny and cute.

[IMG]IMG_0839 by Michael Owen, on Flickr[/IMG]

Continued...

[PeterSibley]

We expect great things of you Falcon ! Anyone who paints like you has the eye !

I recommend joining a forum called AlloyAvenue , everything you need to know.http://www.alloyavenue.com/vb/forum.php

[Falcon1]

I tried to cast a gudgeon from a pattern I had made during class, but it failed. I'll show a photo later. I think I just choked and stopped pouring before it was full.
So my first attempt at home was going to be a re-try of that.

The 2-part mold or flask and the pattern.

[IMG]
IMG_0828 by Michael Owen, on Flickr[/IMG]

You pack the bottom half with sand. In class, we used Delft Clay which is even finer but costs twice as much.

[IMG]IMG_0829 by Michael Owen, on Flickr[/IMG]

Then press the pattern into the sand about half way, then give the surface of the sand and the pattern a dusting of talcum powder.

[IMG]IMG_0830 by Michael Owen, on Flickr[/IMG]

Then put the top half of the mold on and sift sand around the pattern and slowly pack it in really tight. I flatten it smooth with a joint knife.

[IMG]IMG_0832 by Michael Owen, on Flickr[/IMG]

Failure! Even before the pour! I had a bit of trouble in class with this form as well. I think that the sand/clay is amazing and sticks like it's supposed to, but having those two long, tall arms was asking too much of it. Sorry the photo is blurry, but basically, within the arms, the sand didn't part properly.

[IMG]IMG_0833 by Michael Owen, on Flickr[/IMG]

[Falcon1]

So, after that, I decided to try a simpler form, or in this case, two forms. Since they were to have flat backs, like a medallion, I could just press them all the way into the sand and pour directly into the cavity, dispensing with the top half of the mold. When I do a successful 2-part pour, I'll document it, with its pour-spout and vent, which is kind of neat.

[IMG]IMG_0835 by Michael Owen, on Flickr[/IMG]

Looking into the crucible at melting temps. There is a bit of molten bronze in the bottom.

[IMG]IMG_0840 by Michael Owen, on Flickr[/IMG]

I poured the first piece, but I had nowhere near enough metal. The sand catches fire, and often the wood catches too, even if the crucible just near it!

[IMG]IMG_0841 by Michael Owen, on Flickr[/IMG]

So I added a lot more metal, and poured the other piece. Success! Here are both pieces after de-molding. The sand can be re-used many times.

[IMG]IMG_0842 by Michael Owen, on Flickr[/IMG]

Here they are sitting next to the furnace.

[IMG]IMG_0843 by Michael Owen, on Flickr[/IMG]

[Falcon1]

And here is the successful one next to the one I talked about earlier from class. The mold came out ok, just not enough metal!

[IMG]IMG_0844 by Michael Owen, on Flickr[/IMG]

Starting clean-up.

[IMG]IMG_0851 by Michael Owen, on Flickr[/IMG]

And after some grinding, filing, drilling and sanding. Not bad for a newbie!

[IMG]IMG_0853 by Michael Owen, on Flickr[/IMG]

Thanks for looking.

Mike

[PeterSibley]

[Bernadette]

nice work Falcon. I've always been fascinated by "home" casting and i enjoyed your step by step photos.
and yes mr sibley, your work is magnificent! i know of a good wholesome 30' that would suit your winch!

[PeterSibley]

Have you seen this thread Bern? Your comments would be very welcome. http://forum.woodenboat.com/showthre...ite-like/page6

[DeanP]

Wow. I'm in awe. Very cool. I've been day dreaming about going to Europe to buy all the bronze fittings for the Beg-Meil while you cast your own.

Keep up the great work.

Dean

[nedL]

Very cool! Yes I am envious! Nice.

[Charlie Santi]

I am in the process of putting together a foundry. I had an addition built on the shop it's is being sheet rocked with 5/8 fire shield this weekend. I bought a nat gas air furnace with a couple graphite crucibles and the related stuff for it. I have several flasks, riddle, and 200 lbs of petrobond sand. My plan is to make replica hardware and some original for boat restoration. I have also setup and am learning to do pattern work on the computer and making it on a 3D printer. I have done some casting before but the foundry I used is no longer available.

[Paul356]

Not fair! (The windless foto.) But beautiful.

[Jim Ledger]

I'm always up for some bronze casting...and I see Peter's already got the winch on the thread!


Start pourin', Falcon!

[George Ray]

Great Work !
AWESOME !!
.
.
My bucket list has casting on it, and I even have various parts and pieces/tools/supplies waiting/gathering_dust , so inspiration is always appreciated. I did some crude alum pours a couple years back that were fairly easy and promising but my CuAlloy melts were a mess.

[Wagemaker]

Cool...kicks the mind in gear!

WgMkr

[MN Dave]

First, Looking good. I have never seen such clean casting equipment.

Before 'criticising': I have only tried to cast bronze once, in 1985, and it provided me with some nice scrap to remelt. So I will ask some questions about the details that I can't see in the following pictures.

I tried to cast a gudgeon from a pattern I had made during class, but it failed. I'll show a photo later. I think I just choked and stopped pouring before it was full.
So my first attempt at home was going to be a re-try of that.
IMG_0829 by Michael Owen, on Flickr[/IMG]

Then press the pattern into the sand about half way, then give the surface of the sand and the pattern a dusting of talcum powder.

[IMG]IMG_0830 by Michael Owen, on Flickr[/IMG]

IMG_0832 by Michael Owen, on Flickr[/IMG]

Failure! Even before the pour! I had a bit of trouble in class with this form as well. I think that the sand/clay is amazing and sticks like it's supposed to, but having those two long, tall arms was asking too much of it. Sorry the photo is blurry, but basically, within the arms, the sand didn't part properly.

[IMG]IMG_0833 by Michael Owen, on Flickr[/IMG]

I don't see any indication of draft angles (taper), but it is hard to tell from the pictures.
http://archive.hnsa.org/doc/foundry/index.htm#pg36

Figure 37. Mold broken due to a lack of taper.

Figure 38. Clean pattern draw with correct taper.
And on the next page:

Figure 40. Distortion allowance in a simple yoke pattern.

[scott2640]

Wow, so cool.

There is a YouTube series called SV Seeker where a guy is building a 74' sailboat in his front yard. He regularly does his own foundry work for very large pieces. I'm sure you would enjoy it. One time he poured like 50 pounds of bronze for his hydrolic windlass.

[Falcon1]

Thanks for all the comments, everyone. And for the links to more info on the subject.

MN Dave, I think you are right. The instructor was demonstrating on a sculptural form with no straight edges and didn't mention draft. I thought about it briefly when making my patterns, but then forgot. For something like that gudgeon piece, would one just fatten it up all along the middle (parting line?)

Then you'd have to grind/file that flat in the bronze.

Any advice?

Mike

[Jim Ledger]

Any advice?

Mike

I've posted a number of threads on the subject of bronze casting and patternmaking that might be of interest for someone getting started. All written from a beginners perspective with plenty of advice on what not to do...

Making a crucible furnace...

http://forum.woodenboat.com/showthre...nze&highlight=


A bronze casting class at Mystic with Sam Johnson...

http://forum.woodenboat.com/showthre...ass&highlight=


Patterning and casting a catboat steering quadrant...

http://forum.woodenboat.com/showthre...ant&highlight=


Patterning and casting catboat rudder hardware...

http://forum.woodenboat.com/showthre...are&highlight=


...and the ongoing thread about casting a boom gooseneck...

http://forum.woodenboat.com/showthre...ing&highlight=

[jpatrick]

Falcon, one of the easiest things you can do to educate yourself is to visit a chandlery and look at a wide range of cast bronze fittings. I suspect that every fitting you find there has been sand cast. Lost wax is too fiddly and time consuming for mass production. Analyze the fittings by these questions: where's the parting line, how much draft, was a core needed, did the piece distort/why did it?

Jeff

[Falcon1]

Thanks much, Jim and Jeff. I have drawn a new pattern which I
will make tomorrow at work and hopefully test soon.

Jim your furnace is super! I'm jealous! And Jeff, a trip to R+W rope in New Bedford sounds like it's in my future they have a secret stash of (expensive) bronze fittings upstairs.

[PeterSibley]

I tried to cast a gudgeon from a pattern I had made during class, but it failed. I'll show a photo later. I think I just choked and stopped pouring before it was full.
So my first attempt at home was going to be a re-try of that.

The 2-part mold or flask and the pattern.

[IMG]
IMG_0828 by Michael Owen, on Flickr[/IMG]

You pack the bottom half with sand. In class, we used Delft Clay which is even finer but costs twice as much.

[IMG]IMG_0829 by Michael Owen, on Flickr[/IMG]

Then press the pattern into the sand about half way, then give the surface of the sand and the pattern a dusting of talcum powder.

[IMG]IMG_0830 by Michael Owen, on Flickr[/IMG]

Then put the top half of the mold on and sift sand around the pattern and slowly pack it in really tight. I flatten it smooth with a joint knife.

[IMG]IMG_0832 by Michael Owen, on Flickr[/IMG]

Failure! Even before the pour! I had a bit of trouble in class with this form as well. I think that the sand/clay is amazing and sticks like it's supposed to, but having those two long, tall arms was asking too much of it. Sorry the photo is blurry, but basically, within the arms, the sand didn't part properly.

[IMG]IMG_0833 by Michael Owen, on Flickr[/IMG]

Michael, here's a photo I've posted before. A pattern for casting frames for blocks. I always found it difficult to withdraw a parallel sided (without draft) pattern from green sand without breakage and I didn't want draft on these frames.



With this pattern I pack the open section around the acrylic strips with sodium silicate sand being careful not to bend them, rap the acrylic lightly, gas the sand with CO2 to harden it then withdraw the acrylic. This produces a block of solid sand with perfectly aligned and very smooth openings within it the shape of the acrylic.

I then ram up the solid pattern and place the sodium silicate sand core in the opening so formed. A slightly complicated pattern to make but it solved the problem and I had a lot of block frames to cast.

This is the parallel legged block frame from the above pattern.



This hobby presents lots of puzzles, half the fun.

[JasonD]

very nice work Falcon, thanks for posting!

[Falcon1]

Well, I finally got a few more castings done last week. I now have four gudgeons, which will get a 5/16" bronze rod through. This is the system I have on Swift, and I like it.
The two on the left go on the transom. The two on the right go on the rudder. They are rough, but that's ok for now.

Next up, I have made a two-part pattern for a small deck cleat. I'll try to cast it in a few weeks.

Cheers!

Mike

[IMG]gudgeons by Michael Owen, on Flickr[/IMG]

[IMG]gudgeons2 by Michael Owen, on Flickr[/IMG]

[PeterWidders]

Nice work Mike ....they will go very well on the new boat.

[maxwaterline]

Mike, I've made a lot of bronze fittings for my boat by making patterns, having them cast and machining, polishing etc. Didn't really want to get into actual casting at the time (too busy) and many of the pieces would have required a lot of metal. So good on you for having a go

As MN Dave, illustrated above, draw is everything! All the patterns I made had this in mind, on many I marked the parting line so that it was clear. I used cheap MDF "wood", car body filler and grey car body sandable primer for my patterns. I would rather put draw on a pattern and then remove after casting with an angle grinder, doesn't take long, than trying to do difficult pieces without draw, didn't want to stuff the foundry around and ruin it for others. Each to their own I guess. Regards Adrian

[Sailor]

Peter,
In the image of the block frame pattern, does the acrylic part slide out to the left once you've packed the inside of the pattern, then you pack the outside? I think that's how I understand it to work. Am I correct?

[PeterSibley]

Peter,
In the image of the block frame pattern, does the acrylic part slide out to the left once you've packed the inside of the pattern, then you pack the outside? I think that's how I understand it to work. Am I correct?

Yes . The top object is the core box. I pack sodium silicate sand around the acrylic legs being careful not to bend them, gently rap them to get a minute gap, gas the silicate sand with CO2. ( I push a very thin wire into it them inject CO2). Leave 20 minutes and pull the acrylic out to the left. The block of solid sand now has very neat openings in it and will fit neatly into the mould left after I ram up the bottom object , the pattern.

On the right hand end of the pattern ( bottom) you will note a block of wood that would be at the end of the "legs". This is a reservoir for molten metal. When casting jobs like this you will notice that the thin sections cool and solidify first. As the metal solidifies , it contracts and draws molten metal towards itself . I think the gap in this casting might b caused by that.



Thus we need excess molten metal close by for the casting to draw in. It gets a little complicated sometimes but it's relatively easy to avoid.

[Sailor]

Home casting is on my bucket list as well. Thanks Peter.

[PeterSibley]

I recommend joining a forum called AlloyAvenue http://www.alloyavenue.com/vb/forumd...casting-forums .Everything you need to know .

[upchurchmr]

Sorry if this was answered before - I haven't read the entire thread.

What is the practical minimum thickness? As in the "yoke" below.

[PeterSibley]

About 4mm for me, a little under 3/16''. The problem is the molten metal "freezes", loses heat to the sand and solidifies if it has to flow far.

[upchurchmr]

Could you preheat the mold?
I suppose you would have to heat it pretty hot to make a difference.

[PeterSibley]

I haven't tried that as I use greensand, if you were to cast in sodium silicate sand that might be possible ... but having reservoirs of molten metal works well, it's essential really.

[Pitsligo]

About 4mm for me, a little under 3/16''. The problem is the molten metal "freezes", loses heat to the sand and solidifies if it has to flow far.

Peter, have you had good luck with more extensive/multiple spruing/gating, so there's less distance for the metal to flow in the thin sections?

As I've said before, my experience is in the patterns, not the casting.

Alex