Many of the engines and models I make require links - basically a flat piece of metal that holds two holes apart at a specified distance. In most cases, each end of the strip of metal is radiused and the link is tapered such that the tapered sides blend nicely into the radii at each end.
I generally make these as follows. Drill the two holes at the specified separation in a rectangular strip of metal. Put close-fitting pins in each hole and place in milling machine vise so pins sit horizontally on the vise jaws and support the metal strip between the two vise jaws. Put a shim under the small end pin so a horizontal pass with the mill will produce the required angle. Repeat for other side of link so link is properly tapered. I then use a radiusing tool of my own design to form the required radii on each end.
I got tired of rederiving the equations needed to make the calculations associated with this procedure so I wrote the included program. Given the description above, the program should be self-explanatory. If not, email me at mklotz@alum.mit.edu.