I have used 303 stainless, brass and nickel silver pins as far as solid pins go. I have also used mosaic pins that really dress up the knife.
Advantages and disadvantages.
Brass is very nice looking freshly buffed. It will tarnish after a while and it will leave a dull brown patina. Some folks like this, some don't. Brass is also soft.
I can basically state the same thing about nickel silver. It will tend to tarnish to somewhat of a grayish dull patina over time. It is fairly soft as well. Some folks refer to this as German silver.
Stainless does not tarnish. This is a BIG advantage. I use nothing but stainless now for bolsters and finger guards. It will not scratch as readily as the other two materials. To each his or her own, that is just my personal preference. Here are the disadvantages of stainless. It is a little harder to work with. One word of caution, when you are buffing the handle upon completion of the knife, do not over buff the material. There will be humps or high spots where the pins are. This is particularly evident on softer handle materials such as water buffalo and sheep horn, not to mention ox horn, which is particularly soft. Just be aware of this to be a potential problem.
On any of the pin material above, particularly stainless, do not get the pins too hot when grinding the handle material, the epoxy will burn around the pins and look horrible. You don't want to get mosaic pins too very hot at all.
I have never worked with aluminum pins.
CLWilkins
