# Trying lost wax casting



## ghart3 (Jan 4, 2009)

Years ago started on making a 4 cylinder T-head engine called Simplex.  Didn't get all the castings. Main ones missing were the 4 con rods.  Wanting to do lost wax casting thought it would be a good place to start.  This is my second try, first try didn't allow for shrinkage in the rubber mold and in the metal plus couple other things I did wrong.  Mostly finished a new model of the rod that is 6 percent bigger then hopefully the finished size will be.  Shrinkage of 3 to 4 percent for the rubber and about 1 and half percent for the metal.  

The model is made up of 11 pieces silver brazed together.  Didn't get all the seams silver soldered so hope to redo tomorrow without destroying it.  Then hopefully vulcanize rubber mold of the model tomorrow.  From the rubber mold wax patterns will be made.


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## Maryak (Jan 4, 2009)

ghart3,

Very very nice :bow:

Is lost wax the same as investment casting ???

Best Regards
Bob


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## Kludge (Jan 4, 2009)

What metal will you be using for the rods themselves? I'm nowhere near the level to do this (All mine's low temp metal and a little pewter) so I'll be following this closely.

BEst regards,

Kludge


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## jack404 (Jan 4, 2009)

Bob 

yes "investment" and lost wax are similar 

spin is also the same except it has a spun bottle otherwise the same process

nice work ghart3

yes shrinkage guaging is my biggest PITA too

i cast the lock plates and brass butt for my rifles

but have steel alloy molds made for these items, but brass will shink 11% - 17% depending on comp. steel 7%-1%

lead i dunno but its about = to steel ( i do a lot of sinkers )

i do the "try again 'till it fits method " for making fitted items but am getting good at guessing nowdays

the good thing about casting is if it dont work, back in the pot..  ;D and if your lucky you can guess and actually leave it big enough to work without 1/2" of machining needed.  

he can use what he wants Kludg,e 1020 mild steel, 2011 T6 ALU , Ph2 bronze, ( i'm only starting on alu casting and have only done sinker molds so far) but my modified wok burner furnace can do way more than i can i think but the limits of casting are set by you, the process only gets hard with specialist stuff. 

Kludge in US vernackular i'm not fast, casting and its finishes and how fine you can cast dont matter , 

even i have made good steel castings and it has that "esoteric" type feel about it. its a great craft

i like the bit in the movie about the worlds fastest indian motorcycle

thats exactly how home casting is and should be done

( 1 part chevy, 2 part ford and a little lime to clear the s##T out and make it slag up good ) , good movie

cheers

jack


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## Kludge (Jan 4, 2009)

jack404  said:
			
		

> he can use what he wants Kludge



Well, yeah. I figured as much. I was interested in what he actually is going to use. 

Aside from high school, my experience is with lower temperature metals and latex molds, and I doubt crown pewter et al would be of much use in this hobby. I don't know, maybe they would but I'm thinking that's not what he'll be pouring.

In the meantime, I'm still watching and learning and plotting my overthrow of the world one Twinkie at a time.

Best regards,

Kludge


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## John S (Jan 4, 2009)

What temperature will the rubber mould take, or rather what material will it take ?

JS.


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## Tin Falcon (Jan 4, 2009)

Lost wax 101

pattern made from metal.

Mold made from pattern either poured silicone rubber
or natutal rubuuer shhets pressed with heat and vulcanized.
Mold cut from pattern and indexes installed or cut in
wax poured into rubber mold 
Rubber mold peeled away
wax sprues gates attached to wax pattern 
Wax pattern(S) dipped in ceramic or brushed with investment then placed in flask and investment poured around. Vacuum sometimes used to pull out air bubbles. 
Flask(s) placed in oven to cure investment and melt/burn out wax.
Molten metal then poured in hot investment mold. 
Usually with a centrifugal casting setup of some kind.
When cool investment mold is broken away from part and part is finished. 
So the wax copy of the part and the investment mold are both lost in this process. The rubber mold can be used over and over.
This process is comparatively expensive process but poduces high quality parts often needing little finishing other than where the gates and sprues attache to the part. It is typically used to make jewelry but is also used to make gun parts and steel is poured into molds. 
Tin


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## ghart3 (Jan 4, 2009)

Kludge, the metal will be some kind of mystery bronze from my junk pile.  It was some kind of bronze used for electrical contacts in a very large bridge crane.  When melting it didn't give off bunch of white smoke from zinc burning off.  So, I call it bronze.



John the vulcanizing temperature of the rubber is a little over 300 deg. F.  The book says the model must take a minimum of 460 deg. F. for the vulcanizing.  Wish I knew if could get by using soft solder.  Only, seem to recall that it is not recommended. Sure would be nice for fixing flaws and building up fillets. 



Ti, good explanation of the process.  Have built both centrifugal caster and vacuum method of drawing the metal in.  The vacuum method works better for larger sizes.  Sand casting works better for even larger castings. These rods are too big for my broken arm spin caster, so will be using vacuum.


Kf2qd, RTV (Room Temperature Vulcanizing) is one method of doing it.  I will be using a heated vulcanizing press, mainly because a friend gave me one that I was able to fix up.


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## John S (Jan 4, 2009)

John Stevenson  said:
			
		

> What temperature will the rubber mould take, or rather what material will it take ?
> 
> JS.



Reply's to own post [ first sign of madness ? ]

Note to self:-

"What part of lost WAX did you not understand thickie ?"

Now sulking in corner with damp copy of Exchange and Mart over head......................

.


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## shred (Jan 4, 2009)

Good summary TF. Strictly speaking a metal mold to make the wax masters in isn't required; you can build the wax up just from shapes, but unless you're doing one-offs, you don't want to do that. You can also buy wax masters for a vast number of standard jewelry shapes-- blob on a little extra wax, cast away and it's 'one of a kind, hand-made' 

The key (for those that haven't BTDT) is you burn/melt out *all* of the wax before dumping hot metal into the mold (as opposed to lost-foam where the foam is burnt out by the metal)

We always used to drop the hot flask with the cooled-enough-to-not-move metal into a big water tank. The still very hot plaster investment mostly removes itself that way, but it does splash a lot


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## bigal2749 (Jan 4, 2009)

Tin Falcon  said:
			
		

> Lost wax 101
> 
> pattern made from metal.
> 
> ...



Also used extensively in dentistry for gold crowns, other metal copings for bases of procelain fused to metal crowns, and casting frameworks for partial dentures. 

When I was in dental school making jewelry paid for my rent and groceries


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## ghart3 (Jan 4, 2009)

Work some today. Silver brazed missed seams on rod. Cleaned up some and put in metal frame and packed with rubber.  Had to use all the scraps had and barely had enough.





Frame packed ready to be vulcanized.





Vulcanizing.  307 deg. F. for 75 minutes.  Frame has 1/8 holes in sides so excess pressure can be relieved by forcing some rubber out.






Rubber mold split and rod model ready to get out. Notches in rubber is for indexing the two sides, so sides match up when put back like they came apart.





The brass turned all dark, guessing from sulfur in the rubber.  Was hoping to make a wax pattern but air compressor quit working.  If not too cold might work on compressor tomorrow,  hoping it is just start capacitors.


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## Kludge (Jan 4, 2009)

ghart3  said:
			
		

> Kludge, the metal will be some kind of mystery bronze from my junk pile. It was some kind of bronze used for electrical contacts in a very large bridge crane. When melting it didn't give off bunch of white smoke from zinc burning off. So, I call it bronze.



Cool, thanks. The closest I got was a few bismuth mixes to get the idea then crown pewter for decorations for wooden pens since I got tired of the kit junk. The next step was supposed to be gold & silver but I never quite got there; lifus interruptus. (And, yes, I know that's not real Latin.)

Eventually, I'd like to get to brass but that won't be for a long time so I'm using this as pure education. 

BEst regards and thank you,

Kludge


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## Kludge (Jan 4, 2009)

Tin Falcon  said:
			
		

> Lost wax 101



Many much thanks, Tin. This helps a lot.

Best regards,

Kludge


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## kustomkb (Jan 4, 2009)

Thank you all for sharing your info about "lost wax"

I am eager to learn,

Jack,



> ( 1 part chevy, 2 part ford and a little lime to clear the s##T out and make it slag up good ) , good movie
> 
> cheers
> 
> jack



Great movie!

What about the part about Chevy's having a touch of Titanium in the pistons?

Movies love throwing around words like Titanium, Lasers, and now fuel cells, Etc.

All good fun, sorry to clog up the real info, reading with anticipation,

Kevin.


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## T70MkIII (Jan 5, 2009)

I used to melt a little aluminium in a 'flowerpot' foundry when I attempted to build a Gingery lathe a few years back, until kids and renovations - in no particular order - got in the way. I don't know about titanium, but I sure did find a lot of magnesium in some of the old alloy car pieces I picked up from the scrap metal merchant - it made a lovely shade of "too bright to look at".

Which leads me to a slight thread hijack: do any of you melt down your aluminium swarf etc into ingots for re-use in non-critical components? This sounds like a good cost saving idea to me.


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## Metal Mickey (Jan 5, 2009)

Really interesting psot, will store away for the future. Don't pictures say a thousand (or is it 9765?) words!


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## rleete (Jan 5, 2009)

I haven't yet, but I have been saving it with that in mind.


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## Bluechip (Jan 5, 2009)

Hi Folks

If you have a grope around on this site

http://tiranti.co.uk/subdivision_product_list.asp?Subcategory=63&Subdivision=

There is some info on RTV moulds & Low Temp casting alloys.

Never done it myself, but might give an idea or two .

I've had other stuff from them in the past, good firm to deal with, helpful.

Was nothing to do with metal casting tho'.

Dave

The link's a bit screwy .. click 'Casting' on the LH Side takes you to Alloys etc.

A lot of Cold Casting Resin Stuff .. confusing to old varmints such as meself


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## shred (Jan 5, 2009)

T70MkIII  said:
			
		

> Which leads me to a slight thread hijack: do any of you melt down your aluminium swarf etc into ingots for re-use in non-critical components? This sounds like a good cost saving idea to me.


I've thought of it, but there are couple issues-- 6061 isn't a great casting alloy and swarf has such high surface-area to volume that almost all of it ends up as dross and not metal. I'm sure it can be done with the right process-- recyclers buy tons of the stuff, but I don't know the details of what process they use to return it to ingots.


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## ghart3 (Jan 5, 2009)

Did couple wax patterns.  Sure wish would of done core for big end. Ruined first one. Took long time for wax to freeze in big end and had opened rubber mold too soon.  Second one came out ok, think need higher wax temperature.


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## T70MkIII (Jan 5, 2009)

Thanks, shred - I'll give it a go once I have my shop set up, and see what I can come up with.

Looking nice, ghart3 - plenty of trial and error required, but you're getting there. Looking forward to seeing it in the metal. Can you drill the wax out of the big end and replace it with a carburised steel plug? That may work as a core that can be driven out of the finished casting and re-used.


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## ghart3 (Jan 6, 2009)

The wax can be drilled out and no core would be needed.  With investment casting no relief is needed, metal will go only where the wax was melted out.  

What should of done was drill out the metal model and insert pin in the hole.  After vulcanizing the pin slips out of the metal model and goes back in the rubber mold. After injecting the wax and removing,  the pin can be pushed out of the wax pattern,  leaving the hole in the wax.       gary


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## T70MkIII (Jan 6, 2009)

Okay, I see now. When you mentioned 'core' 4 posts up I went off on a tangent, having only done casting from wooden patterns before.


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## ghart3 (Jan 7, 2009)

Made some wax patterns.  Rubber mold is dusted with baby powder so hot wax dont stick to the rubber






Rubber mold lightly clamped to hold halves together without distorting them.






Using home made pressurized wax pot to inject wax into mold.






Left mold clamped for 5 minutes to make sure wax solidified before opening.






11 waxes ready for treeing and investing.





Gary


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## BillH (Jan 7, 2009)

Your going to upload plans for that wax melting pot right?


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## xlchainsaw (Jan 7, 2009)

this is a great thread and im following it closely!


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## cfellows (Jan 7, 2009)

Gary, you sure do make it look easy! And the results are amazing.

Chuck


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## ghart3 (Jan 7, 2009)

Bill, for making a wax injector you might one to see if you can find a small book called "Handbook of Lost Wax or Investment Casting" by James E. Sopcak.  Has lots of "How to Make" articles in there.  Made manual pot like in book and it works good. Only reason made air pot was, well, cause like making tools.  Will try do some info on mine.  Never done one of the PDF things but will give it a go.






Chuck, mostly what makes it looks easy is cause don't take pictures of the goofs and messes that I make.  Actually it is not hard but is kind of involved.

Gary


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## rickharris (Jan 7, 2009)

http://users.frii.com/dnorris/onlineclasses.html this is a jewellery site but has some usable information on lost wax steam casting and silver soldering as well.


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## Kludge (Jan 7, 2009)

rickharris  said:
			
		

> http://users.frii.com/dnorris/onlineclasses.html this is a jewellery site but has some usable information on lost wax steam casting and silver soldering as well.



Coolness! Thanks, Rick. Another site to wander through. 

Best regards,

Kludge


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## ghart3 (Jan 7, 2009)

Good link, Rick.  That is a good way too get started and keeping it simple.
Lots of good info.

My problem is getting free catalogs from the big boys like:
http://www.gesswein.com/catalog/home.cfm?CFID=2195339&CFTOKEN=74423899
https://www.riogrande.com/home/
http://www.grobetusa.com/
Looking thru the catalog and seeing the expensive equipment, I think Gee, got some stuff (mostly junk) that is on hand.  I can make that for all most nothing.  Trouble is it can be long road when should of just got in and done something with what could do with whats on hand as shown on link Rick posted.


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## ghart3 (Jan 11, 2009)

Manual wax pot.  Old hot plate with pot on top, simple hand pump, temperature gauge. Outer shell is old coffee can.





Waxes turned out about 1/16 to long between bearing centers.  Shortened the waxes by taking saw cut out of middle of rod using band saw.





Wax pieces are held in alignment in V-block and welded using hot pen.  Kept pen on in picture only to show it is hot.  This is way to hot for the wax.





Picture showing rod on bottom before cutting and one on top is welded back together. Welded rod still needs little work in welded area to even up.  Working the wax with hot pen is very easy and have much control. Very easy with the hot pen to add just part of a drop of wax if wanted.


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## Alphawolf45 (Jan 11, 2009)

Thats inspirational. I bought some stuff for a try at lost wax casting but havent had the right project come up yet.Id like to see more of this type project.


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## ghart3 (Jan 13, 2009)

Made some lost wax equipment ten years ago after seeing a demonstration and been wanting to do it ever since.  Was lucky to have gone to a 3 day class a year ago. Should of done something right after class but didn't.  Would of been far easier to just machine 4 rods but figured this was as good as any place to start and if I posted as going along maybe will give me incentive to finish this first project.

Having trouble figuring out how to sprue up the con rod waxes.  Thought bigger flask would work better.   Made new 4 and half diameter investment vacuum flask.  





Sprued up 8 waxes all at same level and think will fit in the 3 and half inch diameter flask





8 waxes in 3 and half inch diameter investment flask.  Might be too crowded.  Suppose to have 1/8 between waxes, 3/8 from sides and half  on bottom.   Picture is showing bottom up.


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## ghart3 (Jan 15, 2009)

Little more work on sprues before attaching to base.  Wish hadn't done such a sloppy job.  Got fears hunks of investment will be left after burnout that can be washed into casting when pouring










Base taped on and holes taped over with cheap electrician tape to keep investment from leaking out while pouring.






Found some good information at Ransom-Randolph site on investment. 
They told about using rubber disk for mixing investment.  Made one and was quite impressed at how well it worked and didn't seem to pull any air into mix. Also site has nice calculator for figuring out how much mix and proportions needed.

http://www.ransom-randolph.com/English_measure_calculator_worksheet_jewelry.xls






Mixing with drill press turning about 760 rpm.





Vacuum after mixing about 4 minutes to remove air in mix.






Second vacuuming after pouring in flask.





Vacuum pump set up.  Two vacuum chambers one made from used kitchen canner and the other one from capped aluminum pipe.






Ready for burnout.
Had bought investment at rock shop.  Was a mistake as the investment is old. The gloss over time was about 4 minutes over what is called for.  Next time will buy from jeweler supply place that sells more. 






Burn out oven.  Vacuum cleaner can, soft fire bricks with slots cut for wire and heating element from an electric furnace.


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## ghart3 (Jan 15, 2009)

Investment burnout over night and did pour this morning





Crucible is charged with some bronze with hunk of graphite on top. Not sure if graphite does any good. Thinking it might burn up oxygen in crucible.

This is only third time use for this propane furnace. Made a lifting device so crucible is raised up after metal has melted. Them made a special pouring shank that slides open allowing shank to slip over top of crucible. Lower shank and slide shank close and it has latch to hold in closed position. This works good and am pleased with this system.










Test run before pour, checking for trouble makers.






Bronze melting






Just after pouring.  






Dunking investment with casting in water just after solidifying












Lightly bead blasted to clean up some. Was surprise no shrinkage between rod bearing centers.  Good thing had shortened waxes before pouring.  Maybe there is usable rods in there.  Thinking maybe might redo and cast in aluminum to have lighter rods. 







End of story...............gary


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## Bernd (Jan 15, 2009)

Gary,

A very informative post of investment casting. :bow: :bow: :bow: :bow:

One question, were do you get your ingots from?

Again a very nice thread on casting.

Bernd


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## ghart3 (Jan 15, 2009)

Bernd,  I'm a scrounger and been saving scrap for years. This was all from the same kind of parts, cast electrical contacts.  It looked like color of bronze and lucked out as melted good and got not dross.

If buying ingots, have read silicon bronze is good choice. Also have heard brass boat props are good for casting.  Sorry, not much help.
Gary


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## Bernd (Jan 18, 2009)

That's fine Gary. I don't plan on doing any casting soon. Was just curious as to were you got yours. So it's scrap instead of ingots form a supplier. 

Bernd


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## kustomkb (Jan 23, 2009)

thanks for sharing that.

great tutorial.

are those corn cob moulds? for baking corn?


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## Kermit (Jan 23, 2009)

kustomkb  said:
			
		

> thanks for sharing that.
> 
> great tutorial.
> 
> are those corn cob moulds? for baking corn?



It's an iron corn BREAD baking pan. Granny used one in her kitchen when I was just a little boy.


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## Captain Jerry (Jan 27, 2009)

ghart3  said:
			
		

> If buying ingots, have read silicon bronze is good choice. Also have heard brass boat props are good for casting. Sorry, not much help.
> Gary



Boat props are supposed to be bronze, not brass, however one reason to scrap a prop is de-zincafication due to electrolitic action in seawater. I doubt that they loose all of the zinc but there could be doubt as to the actual composition.

Jerry


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## gilessim (Jan 27, 2009)

Great documentation and those castings look perfect, I don't know about the graphite but recently I bought some graphite rods, in 2 different diameters from a goldsmiths suppliers that apparently are used for stirring the molten metal

good work!

Giles


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## Flopearedmule (Mar 11, 2009)

If you guys want a good read on investment casting. Strictly I.C. issue No. 56
Bruce Satra writes a nice article on the process. Name of the article...."More Wisdom on tapping and The Process of Lost Wax Casting."

I know I read somewhere in the letter to editors, Mr Washburn stated all the magazines are on microfilm.


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## ksouers (Mar 11, 2009)

flopearedmule70  said:
			
		

> I have scanned it to .pdf.....I would probably get into trouble if I was sending copies out??



Yes, you would.
I suggest you review this notice at the top of the plans forum:
http://www.homemodelenginemachinist.com/index.php?topic=4355.0


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