more casting stuff

[Gold Rock]

I thought I'd take a stab at clarifying my gating description I posted on Jim's catboat thread, so here goes. What I'm going to describe is the basic layout for a single part with a single gate. This first photo shows a pattern for a castelated hex nut. I'm showing the layout that would be set up on the drag side of the parting board. The runner is oriented so the gate exits from the side and some runner extends past the gate.

http://farm3.static.flickr.com/2467/4038769394_7ddeed6085_m.jpg (http://www.flickr.com/photos/cshpics/4038769394/)
Note that I'm actually placing a shaped piece of wood to mold the gate. This is very desireable. Gates can naturally be cut by hand, but molding the gates allows precision and control over the shape and size of the gate, as well as mitigating any potential damage caused by a slip of the molding tool.

[Gold Rock]

The shape of the gate is very important. It should be wedge shaped as seen here.

http://farm3.static.flickr.com/2513/4038773352_d617590c3c_m.jpg (http://www.flickr.com/photos/cshpics/4038773352/) http://farm3.static.flickr.com/2766/4038024895_cfe8619492_m.jpg (http://www.flickr.com/photos/cshpics/4038024895/)
What the wedge shape does is concentrate the greatest mass of metal as close as possible to the gate minimizing shrink void potential in the part.

[Gold Rock]

This is the layout for the same part for the cope half of the mold. We have a riser placed directly at the gate and a sprue placed at the far end of the runner. Note that the riser will leave a void completely through the cope. There are certainly times when blind risers or no risers at all are called for, but for most small, loose molded parts I riser all gates just like this.
http://farm3.static.flickr.com/2670/4038022519_fd5acdab82_m.jpg (http://www.flickr.com/photos/cshpics/4038022519/)

The white strip of paper and the white disc under the black core print are just there to represent the positions of the runner and part in the drag. They would, of course, be flush with the parting plane. Note also the sprue. I rarely hand cut sprues. I use sprue plugs as shown. The flat, tapered sides minimize turbulence and potential swirl vorticies from the incoming metal. They also allow you to locate and control the size of the choke at the sprue. Here are a few plugs showing various choke sizes.
http://farm3.static.flickr.com/2597/4038023483_d3fa115d1a_m.jpg (http://www.flickr.com/photos/cshpics/4038023483/)

It's also useful to have a variety of runner sizes and shapes available. Note here the common cross sectional shape of the runners. Again, flat sided to mimimize turbulence and heavily tapered to facilitate clean pulling.
http://farm3.static.flickr.com/2444/4038771810_e408341b1f_m.jpg (http://www.flickr.com/photos/cshpics/4038771810/)

[Gold Rock]

Here's a finished part from the hex nut pattern.
http://farm3.static.flickr.com/2583/4038026399_2e9a998d9e_m.jpg (http://www.flickr.com/photos/cshpics/4038026399/)

And here are two shots showing a raw casting demonstrating all of the above. Note also the generous vent and the strong vent connection. I did not show a vent on the nut pattern as none was called for in that particular case.
http://farm3.static.flickr.com/2437/4038790852_42026c21b1_m.jpg (http://www.flickr.com/photos/cshpics/4038790852/) http://farm3.static.flickr.com/2770/4038041997_87ca06dd8b_m.jpg (http://www.flickr.com/photos/cshpics/4038041997/)

[Jim Ledger]

Thanks for the lesson, Gold Rock.

Couple of questions if you don't mind...

No cup cut under the sprue or pouring basin cut in the top of the cope?

Are square section sprue patterns better than turned round section ones?

The bottom of the sprue seems very small in relation to the runner.

I see there are certain proportions for the sprue, runner and gates listed in books. Do you use certain guidelines to calculate the relative sizes?

When would you use a buried riser? Do you sometimes put risers directly on the part, or always on the gate?

[PeterSibley]

Photos saved for future reference Chuck

[Gold Rock]

Thanks for the lesson, Gold Rock.

Couple of questions if you don't mind...

No cup cut under the sprue or pouring basin cut in the top of the cope? ]

Nope. Often on loose molded parts like this I do without. Adding one wouldn't hurt but frequently isn't necessary.

[Are square section sprue patterns better than turned round section ones?]

As I said, the square(ish) sections discourage swirl and turbulence, though many, many successful castings don't employ this practice. I use them because they have proven reliable for me. You could turn tapered sprue plugs w/a round section and likely have good luck, but if you're going with the plug route, I can make a flat sided plug much faster than a turned round one. The benefits of using a sprue plug are a) control over the choke size and b) they are absurdly easy to remove from the rammed up mold.

[The bottom of the sprue seems very small in relation to the runner.]

This is true. Choking the flow is what we're after. A comprehensive description of choke is probably beyond me, but a fundamental role is to buffer the flow rate of the incoming metal. As you tip the crucible, the velocity of inflowing metal accelerates, and decelarates as you end the pour. A choke in the gating system helps stabalize the metal's velocity as it reaches the gates. More choke for manganese and aluminum bronzes and brasses, and less for silicon bronze.

[I see there are certain proportions for the sprue, runner and gates listed in books. Do you use certain guidelines to calculate the relative sizes?]

Yes and no. The US navy manuals of old (some of which you can still find copies of) have ratios for gating which I use or employ modifications of in certain circumstances. Generally, however, I adjust the relative size of the gating system components by eye and experience. Gate size (cross section), riser size and type, and runner size are important. Too large a runner connected to a part by multiple gates can do harm by distorting or damaging the part as it cools and shrinks. Excessively large risers can create voids in the part by starving it of metal as the risers cool, etc.

[When would you use a buried riser? Do you sometimes put risers directly on the part, or always on the gate?]

The size of the riser depends on the mass of metal in the part to be fed. Very thin wall section parts will call for small, blind (buried) risers, or no risers at all, whereas that bowling ball you're trying to cast will call for a riser as big as the ball itself! And yes, I put risers directly on parts all the time. I'll try to find some pics to illustrate some of these points and post them when I can.

[Gold Rock]

Huh. Sorry Jim. I don't know how to manipulate the 'quote response' format very well. My answers are in between your questions above. I need a tutor.

Chuck

[PeterSibley]

The size of the riser depends on the mass of metal in the part to be fed. Very thin wall section parts will call for small, blind (buried) risers, or no risers at all, whereas that bowling ball you're trying to cast will call for a riser as big as the ball itself! And yes, I put risers directly on parts all the time. I'll try to find some pics to illustrate some of these points and post them when I can.

Chuck ,as a self taught home caster I have to admit to a very poor understanding of the names of various parts of a casting , so please forgive any stuff ups in description .

The risers highlighted above are for shrinkage of metal as it cools ? I have had a particularly steep learning curve when it comes to this problem ....an embarrassing series of mess ups in me earlier attempts ! :o Manganese bronze seems to have particularly high shrinkage .

[Gold Rock]

Yeah, mang. brz. is notorious. It's main problem is that it has a very narrow solidification range. That is, it transitions from liquid phase to solid phase within a comparatively small range of temperature. This means that the thinner sections of a casting will freeze before the thicker sections, depriving them of the ability to draw metal into themselves from the extremities. The net result is that voids, inclusions and tears occur all the time. Risering is often critical. And yes, I'm sorry, risers are sacraficial "sumps" of metal for the express purpose of supplying a reserve of liquid metal for the part to draw from as it cools and freezes. That's why there is such a need to make them as round (ideally spherical) and as closely positioned to the part as possible. You're trying to concentrate the volume of metal (and by extension expose it to a minimum of surface area of the mold) thereby retaining heat and keeping it liquid as long as you can.

[Gold Rock]

Here are some pics of a casting for a chain wheel for a large windlass showing some very heavy risering directly on the part. You can see the four (well, one of them has already been cut off, but..) risers and their size relative to the part itself. This was cast in manganese bronze and the part was a success.

http://farm3.static.flickr.com/2571/4036074629_ffabda09d1_m.jpg (http://www.flickr.com/photos/cshpics/4036074629/) http://farm3.static.flickr.com/2473/4036074043_efa1f1147a_m.jpg (http://www.flickr.com/photos/cshpics/4036074043/)
http://farm3.static.flickr.com/2486/4036073505_fd7822e4d2_m.jpg (http://www.flickr.com/photos/cshpics/4036073505/)

[PeterSibley]

Thanks for that Chuck ....yeah I've finally learned to supply sufficient risers to the mang bronze ...difficult stuff ! Here's a photo of a manganese bronze frame for a wood shelled block ,the eye is a bit small but otherwise it worked well I made quite a few of these .

http://pic40.picturetrail.com/VOL282/9443996/17245530/376540724.jpg


The fun part of this was getting the legs absolutely parallel and feeding the thin sections .Here's the pattern I eventually came up with .The open box on the right side is packed with sodium silicate sand ,set off ,then the acrylic legs pulled .The results are OK.
The pattern on the left is rammed up and the sodium silicate "core section " dropped in .

The block of metal at the bottom of the legs is sufficient feed / riser for the thin sections .Fitting a riser to the eye end ,that is easy to remove afterward is a bit more fun !

http://pic40.picturetrail.com/VOL282/9443996/17245530/376540726.jpg

[PeterSibley]

Here are some pics of a casting for a chain wheel for a large windlass showing some very heavy risering directly on the part. You can see the four (well, one of them has already been cut off, but..) risers and their size relative to the part itself. This was cast in manganese bronze and the part was a success.

http://farm3.static.flickr.com/2571/4036074629_4bda77b3df_m.jpg (http://www.flickr.com/photos/cshpics/4036074629/) http://farm3.static.flickr.com/2473/4036074043_8f97080364_m.jpg (http://www.flickr.com/photos/cshpics/4036074043/)
http://farm3.static.flickr.com/2486/4036073505_a6a4b618d1_m.jpg (http://www.flickr.com/photos/cshpics/4036073505/)

That's interesting Chuck ,I cast my chain wheels as one piece using a core .I'd never thought to do them as 2 parts .:)

[rob]

Thanks for putting this up chuck, but I am not getting any images untill the chainwheel...liker claims you deleated them?

[PeterSibley]

They were up earlier , they're gone now .

[Gold Rock]

Yeah, sorry about the pics guys. I was running out of "room" on flickr. I didn't realize that they would also disappear from this site. I was wondering why the pics I post seem to be 'live links', and Peter's, for instance, don't. Why is that, anyone know?

[Gold Rock]

Interesting take on the block casting, Pete. We've got a number of patterns like that but they're all made with the straps drafted, and so molded without any core. It's nice to be able to take the time such as you have. The old 'time's money' compromise. The chain wheel item is also of interest. By casting them in halves, we can mix and match components for various congfigurations. That toothed sprocket actually pegs on the the chain wheel pattern.
http://farm3.static.flickr.com/2691/4038748752_6954fcd96c_m.jpg (http://www.flickr.com/photos/cshpics/4038748752/) http://farm3.static.flickr.com/2561/4038749302_95f48447cb_m.jpg (http://www.flickr.com/photos/cshpics/4038749302/)
http://farm3.static.flickr.com/2760/4038002291_69d3e2febb_m.jpg (http://www.flickr.com/photos/cshpics/4038002291/)

However, other things can be pegged on as well. A warping drum, or a clutch cone like this.
http://farm3.static.flickr.com/2773/4038000167_4e66da3ba5_m.jpg (http://www.flickr.com/photos/cshpics/4038000167/)
So that you can use the same chain wheel pattern to make a part like this.
http://farm4.static.flickr.com/3500/4038002983_948f533f45_m.jpg (http://www.flickr.com/photos/cshpics/4038002983/)

It's very cost effective.

[PeterSibley]

OK ,so you bolt them up tight together on the shaft ? An interesting idea and as you say ,cost effective .

With my sodium silicate strap pattern , in that job draft on the legs was unacceptable and I'd had a bit of trouble with distortion in the patterns when they were rammed up , even steel moves with a greensand ram up .

The legs in that pattern are acrylic , easy to machine and dead smooth and in all the thicknesses I need .

The pattern was a bit of trouble to make , but I'm very happy with it and will use the technique for all my block frames .A good pattern is time well spent IMO .I'll use it with that great swivel block eye method you showed me !

All bronze swivel blocks ..very nice .:)

[PeterSibley]

Chuck ,I use this photo posting service .It's pretty good .

http://www.picturetrail.com/

[Gold Rock]

Yeah, when are you going to try that casting within a casting technique? I'm looking forward to it. I have on my to-do list for the weekend, to photocopy two editions of old navy foundry manuals. They're chock full of great info and techniques. By the way, you were asking for pics of interesting patterns. The owner of the company has, for years, been dreaming of this project to make a giant cleat pattern so that he could cast them in concrete and use them for benches and such. A few months ago he greenlighted me to make it. Check these out.

Here's me holding a four inch sheet cleat pattern I made and sitting on the 'big one'. It's seven and a half feet long.
http://farm3.static.flickr.com/2691/4038193917_5a616f196b_m.jpg (http://www.flickr.com/photos/cshpics/4038193917/)

Here're a few other sheet cleat patterns I've made over the years, for scale.
http://farm3.static.flickr.com/2662/4038194733_9d72952eee_m.jpg (http://www.flickr.com/photos/cshpics/4038194733/)

And finally, proof positive that it can support a massive amount of weight.
http://farm3.static.flickr.com/2709/4038944056_4025b70436_m.jpg (http://www.flickr.com/photos/cshpics/4038944056/)

[PeterSibley]

Chuck ,you've got a great job !

I'm going to have a go at that job soon , but it would be good to have someone to buy a few first !
I'll need them myself but not for a while .

[Jim Ledger]

Chuck, in case you're not aware, the U. S. Navy Foundry Manual is avaiable as a paperback...

http://www.amazon.com/Foundry-Manual-Us-Navy/dp/1559180072

As you say, chock full of information, and a good read.

I want one of those cleats.:D How was the female mold made and the concrete cast? What's the bronze finish?

[Gold Rock]

Jim, I have the manual that's being reprinted by Lindsay Publications, but that's the one given to the mids in training. There are a couple of other publications that were produced for the experienced founders for use in teaching. The copies (actually copies of copies) that I have access to are from the early fifties.
The big cleat mold was made by building a plywood box big enough to surround the pattern and was then backfilled with a chemically bonded sand. A skeletal framework of steel reinforcing rod was suspended within the mold cavity prior to pouring in the concrete. The reddish color is just auto body primer from a spray can.

[PeterSibley]

Chuck ,a request ?

Could you list the various commonly used bronze alloys ,say silicon bronze , leaded bronze ( what we in Oz call LG2 or gunmetal) ,phosphor bronze ,aluminium bronze and my worst enemy ,manganese bronze , in terms of their ease of casting (ie shrinkage etc ) and then machinability ?

I know this is a bit of an ask but you seem best qualified here to answer.....and it would be very useful information to the various readers .

[RT MAN]

This is great thread very informative. I'm going to be casting these lost wax parts for my sail boat. I would like to cast them on a christmas tree cleats on one and pulley's on another. I have no idea how to set sprues, risers and gates. any ideas?

http://i46.photobucket.com/albums/f118/Alerion111/IMG_4190.jpg?t=1256395533

http://i46.photobucket.com/albums/f118/Alerion111/IMG_4191.jpg?t=1256395593
Rufus

[PeterSibley]

Rufus , in my websurfing I've come across investment casting group,usually concerned with jewellry casting .Perhaps they would help .I've never done investment casting .

Very nice waxes BTW ,what wax are you using ? Silicon molds ?

There are couple of interesting bits on this site .http://www.foundry.ray-vin.com/

[Gold Rock]

Chuck ,a request ?

Could you list the various commonly used bronze alloys ,say silicon bronze , leaded bronze ( what we in Oz call LG2 or gunmetal) ,phosphor bronze ,aluminium bronze and my worst enemy ,manganese bronze , in terms of their ease of casting (ie shrinkage etc ) and then machinability ?

I know this is a bit of an ask but you seem best qualified here to answer.....and it would be very useful information to the various readers .

Well, the alloys I work with most are C86500 manganese bronze, C87300 silicon brz. (Everdur), and C95500 aluminim nickel brz. There are other brasses, bronzes, copper/nickel alloys, as well as plain aluminum that come into play from time to time. I am not, by any stretch, a qualified machinist, but silicon and mang. bronzes machine pretty nicely. AlNi brz. can be more of a bugger, though within my limited range of skills I manage to do well enough with any of them. Straight alum. alloy (I know what that sounds like, but you know what I mean..) is a pain. It galls something awful. Machining castings is always an adventure. As well as the constant irregularity of their physical shapes, you're always at risk of discovering a void or inclusion. Good times.

[Gold Rock]

Hey Rufus,
Investment casting is not my thing at all. We have poured a few shell castings that were brought to us by customers. My take on it is that it is a fantastic way to get a good casting. The major upside in my limited experience is that since the molds are heated in a kiln or furnace prior to pouring, you consistently get a very high quality casting in terms of metalurgical integrity. It is also because of this preheated shell that risering, if required at all, is in a different book from sand casting. Gating the parts is similar in many ways, though because of the multiple part arrangement on a single sprue tree and the peculiarities of venting in this type of casting, all I can do recommend a book on the topic. Wish I could help more. I will say, if you progress successfully in your endeavor, post some pics so we can see the process. Cool stuff.

[PeterSibley]

Well, the alloys I work with most are C86500 manganese bronze, C87300 silicon brz. (Everdur), and C95500 aluminim nickel brz. There are other brasses, bronzes, copper/nickel alloys, as well as plain aluminum that come into play from time to time. I am not, by any stretch, a qualified machinist, but silicon and mang. bronzes machine pretty nicely. AlNi brz. can be more of a bugger, though within my limited range of skills I manage to do well enough with any of them. Straight alum. alloy (I know what that sounds like, but you know what I mean..) is a pain. It galls something awful. Machining castings is always an adventure. As well as the constant irregularity of their physical shapes, you're always at risk of discovering a void or inclusion. Good times.

OK ,having asked the question ,I'll add my 2c worth .:)

Manganese bronze is nasty ! It shrinks a lot ,more than most other bronzes ,so needs huge feeds .It's fine to turn with carbide tooling ,in fact it's very good .Drilling it with HSS drill bits is a disaster ! It's a great way to stuff a bit quickly ....but I'm a lousy machinist , someone who knows what he's doing might be OK .
That's the down side .The upside is that it is tremendously strong and abrasion resistant ,the particular alloy I use runs 70,000 psi tensile .

Leaded bronze !(Gunmetal or LG2 in Oz ) Lovely , low shrinkage , runs well ,machines well ...half the tensile of manganese br.It's the Oz foundryman's favorite , the way silicon bronze seems to be in the US .

Phosphor br .I cast a little bit of this .Similar to LG2 , but perhaps not quite as easy .

[RT MAN]

Silicone molds were used and they pick up every micron of detail. The wax is a casting wax made from Beewax it is hard wax. I can't remember the name of it. While casting the wax shell block patterns I was getting little divets in the top of the shell at same spot it took about 15 tries before I made some vents which eliminated the divets. I figure I would possible attempt the same casting position for the SB. These pulley's are actually to small for my boat but I had one so I thought I would use it as a ginny pig because it was the first try. So now I will make the Sprue, gates and vents. This will take some thinking I'm sure.


I'll check the new web site for new ideas
Thanks guys
The cleats will be simpler I hope.

th

[PeterSibley]

Rufus , the reason I asked is that "normal "waxes expand a little just before they liquify , this can result in a cracked investment if a hard modern investment is used .I did some reading a while ago on how the ancient casters (and the modern fellas in Nepal etc ) do this .Apparently they use / used a flexible investment with a high percentage of cow manure in it .Interesting stuff .Your local library may have information on this .Some of the "primitive " techniques give brilliant results at much less cost .You only have to look at the art casting from the early 19th century and things like Pelton wheels cast in village foundries in Nepal .

Good Luck and please keep us posted !

[Gold Rock]

OK ,having asked the question ,I'll add my 2c worth .:)
Manganese bronze is nasty ! It shrinks a lot ,more than most
other bronzes ,so needs huge feeds .It's fine to turn with carbide tooling ,in fact it's very good .Drilling it with HSS drill bits is a disaster ! It's a great way to stuff a bit quickly ....but I'm a lousy machinist , someone who knows what he's doing might be OK .
That's the down side .The upside is that it is tremendously strong and abrasion resistant ,the particular alloy I use runs 70,000 psi tensile .

Peter's points about variations in shrinkage are useful to bear in mind when considering alloys, but I think it should clarified that manganese bronze doesn't shrink appreciably more or less than other common brasses and bronzes. It differs in the way it cools and freezes. Not all liquids freeze the same way. Metal molecules in bronzes, for instance, go from slipping and sliding around and about one another in a liquid state until, when they've lost enough heat energy, they bind with other like molecules in a crystal matrix. The difference comes in the form of the amount of rigidity, if you will, of the newly formed matrix. The matrix of an alloy like Everdur stays 'flexible' or 'not quite frozen' for a longer period of time, allowing the whole of the casting to re-shift it's form while the liquid filled denser sections are still cooling and shrinking. Manganese bronze, on the other hand. achieves a final rigidity of it's molecular matrix much faster, so that once an area of a mang. casting has frozen it will no longer move to accomodate the loss of space created by parts that are still liquid and have yet to freeze. The result is that the remaining areas of the form to cool, instead of drawing the rest of the part to themselves, tear themselves apart to go meet the areas already frozen. To all you metallurgical engineers, I appologize for this lame paraphrasing of a very precise science, but I think the explaination will make the point.

[Jim Ledger]

Manganese bronze is the stuff of propellers and shafts?

[PeterSibley]

Thanks Chuck ,a good explanation of something I didn't really understand .All I know is I have to feed slow to cool sections very well .Another disadvantage of the stuff is that the zinc burns out as it is reused ,something to be avoided in high spec parts .I do add a bit of zinc to non critical pours .

Jim ,high strength parts ,props , windlass gypsies ( chain wheels ) .I tend to use stainless for shafts .

Chuck might explain why manganese bronze props don't dezincify ?

[Gold Rock]

Thanks Chuck ,a good explanation of something I didn't really understand .All I know is I have to feed slow to cool sections very well .Another disadvantage of the stuff is that the zinc burns out as it is reused ,something to be avoided in high spec parts .

Dead on Peter. Manganese bronze is indeed an attractively strong alloy. As far as I know, mang. props do de-zinc, though the rate may be suppressed somewhat by the fact that there is almost always a sacraficial zinc mounted in the proximity. I would suspect it's use is also because the alloy possess other physical properties that are of value in either the manufacture of or performance of the propeller. I believe I noted, perhaps from the Copper Development Assn., that the US Navy prefers one of the aluminum bronzes for propeller applications. The C95500 alloy is a surpassingly corrosion resistant alloy as well as being significantly stronger in most performance characteristics than manganese bronze. One aspect of manganese bronze's popularity is undoubtedly cost. It's composition is over one third zinc (it's really a high strength yellow brass, to be fair), and zinc is comparatively cheap. An unavoidable reality.

[PeterSibley]

I think you mentioned that aluminium bronze are a pain to machine Chuck ? I wouldn't mind learning to use another high strength alloy but only if it offers some advantages over mang bronze ...seeing I have abour 500 pound of man. br in ingots waiting to be used .:D

edited to add , something that doesn't dezinify immersed in the bilge.

[Gold Rock]

I didn't mean to imply al.brz. is tough to machine. Merely a bit fussier depending on the operation, but definately nothing that should put you off. I'm a big fan of it. I've replaced all of the hardware below the waterline on my boat with C95500 castings. It's no fussier than mang. to pour, really, though it requires higher pouring temps; closer to those of sil.brz. And it has a tensile strength in the neighborhood of 90-95,000 psi and is exceedingly corrosion resistant. I love it. Manganese is great stuff, though. If it's above the waterline, it's great. As a rule, we pour chainplates, all windlass parts, bowsprit heel sockets, cruciform bits, anything where high strength is a virtue, with it. Definately a worthy material.

[Jim Ledger]

Chuck, I was going to use a piece of inch and a quarter propeller shaft for the pins on those pintles that I cast. Do you see any problem with TIG welding them to the silicon bronze bodies with silicon bronze rod?

Does it weld easily, give off zinc fumes?

[PeterSibley]

I didn't mean to imply al.brz. is tough to machine. Merely a bit fussier depending on the operation, but definately nothing that should put you off. I'm a big fan of it. I've replaced all of the hardware below the waterline on my boat with C95500 castings. It's no fussier than mang. to pour, really, though it requires higher pouring temps; closer to those of sil.brz. And it has a tensile strength in the neighborhood of 90-95,000 psi and is exceedingly corrosion resistant. I love it. Manganese is great stuff, though. If it's above the waterline, it's great. As a rule, we pour chainplates, all windlass parts, bowsprit heel sockets, cruciform bits, anything where high strength is a virtue, with it. Definately a worthy material.

I was thinking of floors in Al bronze but might just use LG2 ( your C83600 ?) ,it's easy to work and I have a few ingots here .

[Gold Rock]

Chuck, I was going to use a piece of inch and a quarter propeller shaft for the pins on those pintles that I cast. Do you see any problem with TIG welding them to the silicon bronze bodies with silicon bronze rod?

Does it weld easily, give off zinc fumes?

Jim, any high zinc alloy welds terribly. On top of which, old 'high zinc' alloys (like, potentially, old prop shafts) may have lost significant amounts of said zinc (and consequently most of their strength). And lastly, no high zinc alloys are appropriate below the waterline. All the fittings for my boat were cast in manganese bronze thirty some years ago. Their codition when I finally replaced them was appalling. The rudder fittings were ground to dust and slopping all over the place. The bobstay fitting was so de-zincified that it actually snapped in two pieces while I was docking on a windy day. Fortunately no part of the rig was damaged, but I was a bit shaken. The idea of casting the pintles and putting the pins in separately is a good one. I cast my holes undersized, then reamed them to a press fit, pressed the pins in and drilled them for a cross pin which was also a press fit and finally peened in place. The best part is that as the pins wear (eventually), you (or your grandkids, more likely) can press them out and relplace them.

[Gold Rock]

I was thinking of floors in Al bronze but might just use LG2 ( your C83600 ?) ,it's easy to work and I have a few ingots here .

C95500 would make the world's best floors, no doubt about it. A little research however, shows that C83600 (Cu 85% Pb 5% Sn 5% Zn 5%), has decent corrosion resistance and strength and would make terrific material for floor applications, (especially if you manufactured the keel bolts from the same material!).

[PeterSibley]

Chuck ,keel bolts are 7/8" copper , as is normal practice here .All fastenings in fact are copper except silicon bronze garboard and hood end fastenings .

Keel bolt nuts are C83600 .

As an aside , how do you cast small nuts ? I made up a pattern board but was dissatisfied with the result .I'm now casting 10" lengths of C83600 hex bar using 3/4" aluminium extrusion as a pattern ....then cutting them of 3/8" thick ,boring and tapping.

[PeterSibley]

Jim ,this is one way of attaching stainless to a casting ,the 5/8" round bright stainless was bored on the lathe then cross bored .When the eye was poured around it it was pretty successfully locked in place .

http://pic40.picturetrail.com/VOL282/9443996/17245530/376665866.jpg

Not really replacable though !

[RT MAN]

Rufus , the reason I asked is that "normal "waxes expand a little just before they liquify , this can result in a cracked investment if a hard modern investment is used

Peter this wax is made for casting and doesn't expand according to the person that sold it to me. Actually this was the first question I asked.

My concern at this point is the curing the plaster mold because I don't have oven to do this in. I've seen several internet videos of people pouring straight into the mold just encased in sand. From what I could tell there was no curing involved just a proper drying time and aquick melt out.

This is entirely experimental. Getting the wax out will be easy, baking the mold to 1300 degrees in an oven will not be unless I find an oven of sorts.

[Gold Rock]

As an aside , how do you cast small nuts ? I made up a pattern board but was dissatisfied with the result .I'm now casting 10" lengths of C83600 hex bar using 3/4" aluminium extrusion as a pattern ....then cutting them of 3/8" thick ,boring and tapping.

Yep, that's the way to do it. Just pare them off the bar stock as you need them. You can cast the pattern solid, or put a small core print in there.

[PeterSibley]

Rufus , the reason I asked is that "normal "waxes expand a little just before they liquify , this can result in a cracked investment if a hard modern investment is used

Peter this wax is made for casting and doesn't expand according to the person that sold it to me. Actually this was the first question I asked.

My concern at this point is the curing the plaster mold because I don't have oven to do this in. I've seen several internet videos of people pouring straight into the mold just encased in sand. From what I could tell there was no curing involved just a proper drying time and aquick melt out.

This is entirely experimental. Getting the wax out will be easy, baking the mold to 1300 degrees in an oven will not be unless I find an oven of sorts.

Rufus , as you probably have seen on this site http://www.foundry.ray-vin.com/
sheetrock plaster is sometimes used , but IIRC only for low temp alloys .I've certainly seen it done with aluminium with a good result .Bronze is very hot and the results are not as good .I'm afraid I can't help but there are several very good books .The art casting section of your local library is a good place to start .

I'm very glad you got the right wax sorted , it's the easiest mistake people make .:)

IIRC the re is a group out there on the net called Artmetal ,it might be worth looking for them.

Good Luck! and please keep us posted , we all have a lot to lean about this technique.

[S B]

Hi, any advice for the"poor folk":D who have to scrounge the junkyard for their bronze? For example;most water taps are this alloy or all automotive gears are likely to be? Best guess is better'n nothing to work with.

[PeterSibley]

I'll let Chuck take that one , you blokes use different alloys to us .

[Gold Rock]

Hi, any advice for the"poor folk":D who have to scrounge the junkyard for their bronze? For example;most water taps are this alloy or all automotive gears are likely to be? Best guess is better'n nothing to work with.


There's nothing wrong with melting down copper based scrap. It does matter what you want to cast with it. For example, if you're casting decorative shelf brackets, it doesn't really matter what you use. But if you're casting a through hull or rudder fittings, it does matter, as galvanic nobility is required. Likewise, if you're casting rigging fittings, where strength is paramount, you must know the exact composition of the alloy so that you can make reliable calculations regarding strength. Most commercially mfr.'d plumbing fittings are brass, not bronze. Beyond that, I don't know how one would know the specific alloy of a given 'found' bit of metal short of identifying and inquiring of the original manufacturer. That would seem somewhat... daunting. Melting scrap can be a nuisance in terms of dross, slag, and unknown fumes. But free is free, and free is a good price.

[rob]

This is an interesting queston to me as well. I have been told a couple of times that silicone bronze is very touchy about lead contamination....and that really I should keep my crucibles seperate by alloy. Well, crucibles aren't cheap and so I have never bought one just for scrap melts. This keeps me from doing them. I often am tempted to for the kind of decorative/art work since as you point out free metal is nice (in terms of price)and I can't justify using good everdur on playthings and practice. Any thoughts...or have I been given questionable advice regarding alloy sensitivity?

[PeterSibley]

It's good abvice Rob , lead andsilicon can form leaded glass which is a very unpleasant inclusion in your casting .You'll have to buy another crucible soon enough , buy it early !