CASTING PARTS FROM TIN OR ZINC?

[Kegan]

Hi everyone

I am new to casting but have been collecting materials to melt for a long time. I have only just recently gotten a house and a workshop and am planning my first foundry/furnace build in the next few month.

I have collected cast aluminium and cast zinc and tin items. Ive been learning to tell the difference lately, density seems to be a tell tale indicator. Items like belt guards can be made from aluminium quite easily and the material seems to suit such applications. But items like the base of machines, lathe beds and such call for a heavier material like cast iron. Take the Quorn tool cutter for example.

So has anyone used tin or zinc or zamak or alumimium-bronze to make parts for projects like the Quorn etc? I noticed my Myford ML7 Apron is made from a metal that is not aluminium or cast iron, correct me if I am wrong.

If this topic has been covered sufficiently please accept my apologies and point me in the right direction. If you have experience with any of this please share. I like to experiment and my budget is tight so I like out the box ideas. Simply buying ingots of the right type of material is not an option for me at this time.

Thank you for your time

Kegan

 

[ddmckee54]

Some of the Unimat DB/SL lathes had parts that were cast from aluminum and some had parts that were cast from zamak. These were all die-cast parts. I believe that some of the zamak parts would tend to "creep" if they had a cantilevered load on them for long periods of time. That's why you didn't want to leave the Unimat in the mill format for months/years on end. I believe that zamak would be the preferred material for anything that doesn't have weight hanging off from it, due to its' higher density.

 

[aka9950202]

Keegan, look for the Gingery lathe book. He makes a lathe from aluminium and some steel

Cheers,

Andrew in Melbourne

 

[Kegan]

Thank you for the responses

 

[mrehmus]

Zamac, or ZA 18 or ZA28 is aluminum alloyed with either 18 or 28% zinc. It is stronger and heavier than aluminum and makes great bearings. The gears on my old 6" Craftsman metal lathe were one of those alloys and they were in perfect shape 40 years after they were cast. The alloy melts at just under 1,000 degrees F and shrinks about 1%. And it machines like a dream. It is also used to make costume jewelry using the spin casting method which, in itself, is very interesting.

 

[Vietti]

I agree with Mike, Zamac is underloved by our community. Besides the above mentioned properties it is almost as strong as cast iron. Mike's MEB magazine carried an article on making molds for Zamac from segmented aluminum plates. I have made many magneto housings from this material using aluminum molds with success.

 

[GreenTwin]

I experimented with some Zamak27, which is some very strong material.
The low melting point is a good thing as far as melting and casting the metal, but I found that when I tried to drill it, the material basically melted in front of the drill point.

Others have said the melting problem can be solved by using some lubricant when drilling/machining zamak.

I have also experimented with aluminum alloy 356, and I found that it requires just slightly more heat to melt than zamak.
While 356 does not have the mass of zamak, it can be tempered to an approximate T6 hardness using a two-step process, and this makes for some very nice hard and easily machinable aluminum, without the problems of tool loading/gumminess that you can get with untempered aluminum.

Hope this helps.
.

 

[Vietti]

Green Twin,

I've drilled, tapped and machined lots of ZMAC and never experienced the problem you describe. I wonder if you alloy was bad or the drill was woefully dull. To melt the material your bit was creating +700 degrees!

Suggest you try again with a known alloy and a sharp bit. It's too wonderful a material to disregard.

 

[GreenTwin]

I think Zamak has great potenial for many model builders/casters, especially in some of the stronger grades.

I gave up on brass, bronze, aluminum, and zamak, and only cast engine parts in gray iron now.
I realize that casting gray iron is not an easy step for most, and so zamak may be a good choice for many.

A quick internet search shows Zamak 27 to melt in the range of 708-903 F.

Aluminum 356 has a melting range of 1035-1135 F (a second source says 1220 F).

So the differential between the melting points of Zamak 27 and aluminum is perhaps in the 300F range.

300F means leaving the burner running for 5 more minutes, which is hardly even noticable.

So I hear folks making a big deal about the low melting point of zamak, but in reality, I use the same propane burner, the same crucible, the same furnace for either, and aluminum requires a few more minutes of heating.

If I did not know ahead of time which metal I was melting, I would not even notice the difference in melt times.

I am not knocking Zamak, just pointing out some things I discovered when comparing it to aluminum melts.
Every metal has its good use based on its distinct qualities.
One should not choose to use zamak only because it has a slightly lower melting point than 356 aluminum, because it is simple to melt both zamak and aluminum 356 using the same equipment, with similar melt times.

The mass of zamak is hard to beat for things like flywheels.
For larger scale engines, casting the frame and other parts in 356 aluminum is desirable, since it keeps these parts at a reasonable mass.

I think aluminum performs much better at elevated temperatures, whereas zamak does not perform well above I think 400 F (check me on that).

.

 

[Vietti]

Good points. I melt the Zmac in an electric pot designed to melt lead for sinkers etc. Very simple. Using segmented aluminum molds some rather complicated parts can be made and the mold is not destroyed

 

[GreenTwin]

I have not heard of using aluminum molds with zamac.

That is an interesting application for sure.

Do you use a mold coat on the aluminum molds to help with release?

.

 

[Vietti]

Yes a coating is used. I hope Mike Rehmus will jump in here and say what issue of his MEB magazine covered the technique. If not, I can dig thru the old issues and figure it out (maybe). Anyone else remember??

 

[DKGrimm]

Interesting thread here on aluminum and Zamac. Not sure if ZA-27 qualifies to be call Zamac or not, but it is all the things that have been described. Besides that, it is very fluid when melted and conforms to sand molds down to the finest detail. Also, unlike aluminum, it is highly corrosion resistant and is an excellent bearing material, so it is a good substitute for bronze for things like water pumps. Also heavy enough to make decent flywheels.

 

[GreenTwin]

Here is a website with descriptions of the various Zamac alloys:

https://dynacast.com/en/knowledge-center/material-information/zinc-casting-metals

And here is a pdf file comparing Zamak (Zamac ? I see it spelled multiple ways) with other metals:

https://cwmdiecast.com/wp-content/uploads/2021/06/2021-NADCA-Zinc.pdf
.

 

[GreenTwin]

Zamak seems to be good for mass-produced items, especially with die castings.
One site mentions that the lower melting point does save energy.
One would not really notice the energy savings so much in a home foundry setting unless perhaps you did a lot of casting work.

It is very strong material, especially as the Zamak number goes up.

.

 

[DKGrimm]

Yes a coating is used. I hope Mike Rehmus will jump in here and say what issue of his MEB magazine covered the technique. If not, I can dig thru the old issues and figure it out (maybe). Anyone else remember??

Model Engine Builder Issue #19, page 23.

 

[Vietti]

Also issue 16 describes using MAXAC in sand casting. I used segmented aluminum molds with success. The segments are made top and bottom and the mold is held in position with blank plates on each end and thru bolts. Jacking screws are provided to free casting from mold. Each segment can have a different shape so some complex shapes can be fashioned. Maxac seems like it would be useful to cast parts from printed prototypes.

 

[Mechanicboy]

MAXAC is fault word. It's ZAMAK, zinc alloy, easy to melt and strong near as cast iron.

https://en.m.wikipedia.org/wiki/Zamak

 

[Steamchick]

Just searched for MAZAK - the name I have used since I was first taught about the Zinc alloy in the 1970s.... - used extensively for thin walled castings for cars.... things like alternator brackets, wing mirror armatures, etc., Model cars (Triang/Dinky, etc.), and hosts of other things. Ideal for model makers to make low-temperature castings of flywheels, etc, where they want mass without cooking the metal to red-heat, etc. and pretty cheap from scrapyard car parts.
But MAZAK doesn't appear as a Zinc Alloy... I remember someone saying "that stuff is dangerous in a fire because it is Zinc" But Magnesium castings are more dangerous. - Then I was told "It is MAZAK, a Zinc alloy, not pure zinc...." - We melted loads of it in a steel bucket on a wood fire and poured it into crude moulds for scrap sale, thus removing any steel scrap that was in the castings (Inserts, rusty bolts, etc.). I was told it needed an arc welder to ignite it, so it was safe on the wood fire... But not to play with Magnesium castings - which were easily identified as they are so light - and very dangerous if ignited!
So maybe my "folklore" education wasn't perfect?
I thought ZAMAK was a trade marked name for the alloy, so MAZAK was the generic term for the magnesium-zinc alloy. (I was wrong on that one!). However, the wonderful "Wiki" interpretation -
From Wikipedia, the free encyclopedia (Built by the "un-knowing" contributors? - Who do not spell it "Encyclopaedia"?)

Zamak ingot
ZAMAK (or Zamac, formerly trademarked as MAZAK[1]) is a family of alloys with a base metal of zinc and alloying elements of aluminium, magnesium, and copper.

So maybe I am just "old fashioned" calling it MAZAK, not "modern speak" calling it "ZAMAK"?

And I am still struggling with the language calling Motor CARRAIGES, abbreviated to "Motor Cars" - or more simply just "CARS" - called "Autos"... as they are not in many ways Automatic?
But this is just a modern sales corruption that is generated by "the first" in an industry to use the unique name to differentiate their product from the rest. - "CARS" in the US of A was originally a term used for RAILWAY CARRAIGES - I think? - Long before the Europeans developed Motor Cars, or Mr Ford invented "Autos" - because he utilised an Automatic transmission, seemingly because he struggled with the manual gearboxes at the time? - And expected the owners and drivers of his Autos to not want to know or use the complex driving technique of a clutch and manual gearbox? (Gear-shifter).
Language is such a beautiful thing, evolved or corrupted by the innocent, or by sales people who want to make money by changing it somehow.
K2

 

[Steamchick]

P.S. Thanks for all the useful information above gents, I enjoyed your posts above.
K2