I don't turn, but I have sanded Purpleheart more than a few times back in my humidor-making days. Sounds like to me you are sanding the end grain. Are you cutting the plugs by entering the wood into the long grain? If so, you need to buy thicker stock and enter the wood at the end grain. This will give you long grain to sand on and will come out more consitently.
This may not be possible as the plugs will be weaker by comparison. Depends on your application. You may need to find cutters that will tear the fibers less than the ones you are presently using. IOW really really sharp, high quality plug cutters and go s-l-o-w as you cut.
Go for the long grain if you can use it that way. If not, you have to find a way to have the exposed end grain less porous after your cuts. Different porosity will look different no matter how much you clean it up after sanding.
Last edited by TexasTimbers; 03-24-2008 at 10:23 AM.