Although I wish I could say yes, they are metal, I'm casting all my parts with a urethane resin since I am very familiar with it. As much as I would like to, I have not had the time to experiment with metal casting yet.
I have not given up though. I have spoken to some metal casting shops and I am working on a new Solidworks file of the track link that will lend itself to spin casting in metal. If it proves cost effective and there is enough interest to justify it, perhaps I will move forward with that option.
Also, when looking at making the rear idler last year I had it quoted by a metal, rapid proto company where they actually grow the part much like an SLA only it's in any metal you want. The nice thing with this process is undercuts are not an issue. This would allow, possibly, for functional, accurate track link replacements. Of course the cost is also more then spin casting but maybe in large quantities, and for the smaller part track link it would be less.
My problem is I'm not prepared to make the jump from hobby to business. I already have a full time job I love that does not leave me much free time as it is.
Probably more info then you were looking for.
Thanks again everyone for the great comments.
Kind regards
Tim