If you use extruded aluminum you'll loose the hardness that the extrusion has. To get some of this back you'll need to remove the casting while still hot. then quench in cold water, well away from the furnace. Or you'll need to heat treat the casting.
Dave Patterson
odd_kins@yahoo.com
http://home.comcast.net/~oddkins/foundry_home.html
--- On Sun, 2/27/11, james <james122964@yahoo.com> wrote:
From: james <james122964@yahoo.com>
Subject: [gingery_machines] Re: New Here
To: gingery_machines@yahoogroups.com
Date: Sunday, February 27, 2011, 4:57 PM
So, it would be better to use the extruded aluminum? or should I hunt around for actual cast aluminum?
I sure wish the die cast stuff would have been worth it, as it melts a lot easier and is heavier, guess I could use it for pulleys.
Jim
--- In gingery_machines@yahoogroups.com, David Frantz <websterindustro@...> wrote:
>
> Long ago I worked in the die cast industry so I have some experience with this. First die cast alloys are not the same as zinc based casting alloys designed for sand casting. Second die cast alloys age significantly of time. Third die cast alloys are sensitive to the ratios of metals which means it is easy to get fining results if the alloy varies from the accepted ratios much.
>
> Given that you wouldn't have any problems pouring a Zinc die cast alloy. The low melting points mean that you can get by with a cheaper furnace. Sources for the alloys where at one time cheap and plentiful (carburetor and other auto parts). Zinc die castings can have initial strengths equal to similar cast iron parts. So there are good points to consider with respect to Zinc castings.
>
> The bad points are also worth considering. One in this context is that a Zinc casting might not be as dead as a cast-iron or aluminum one. That is you may see much more in the way of ringing and vibration transmission. As mentioned above the alloys do age over time which might result in a need to re scrape parts overtime. Actually all cast metals have an aging factor it is just that some Zinc alloys can age more than others, plus this is in the context of die casting.
>
> In the end I would NOT recommend zinc die cast alloys for most parts of a lathe. I just think you would get far better results from other materials for most of the structure.
>
>
> On the granite:
>
> Granite counter top material can pass as A surface plate. You should check the flatness your self and make sure it is well supported to prevent bending under use. Simply due to the thickness it ought to be a better starting point for a surface plate than ceramic tile or other things that are often suggested. In any event realize that a surface plate requires maintenance just like every other tool.
>
>
>
> David A Frantz
> websterindustro4at4mac.com
>
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