Hi Ralph, here is a side view it is gloued up out of some scrap plex that I had kicking around. The arm is 1 inch thickand the base is a couple of layers of 1/4 inch white plex. The punches are just 1/4 inch diameter bright mild steel, I use for styrene and thin annealed brass so the punches work fine the big brass handle is threaded 1/4 x 20 and fits on all the different punches basically just different ball sizes at the pointed end.
The brass anvils are made from 3/8th diam and sepped down to 1/4 diameter on the bottom side, and the top varies with the rivet size.
The stop is 1/4 inch clear that has been frosted with emory cloth and slides bad to allow the sheet to be positioned exactly where you need it.
The punch just drops into the brass bushing and returns buy virtue of the compression spring.
A couple of shots showing the way the anvil is used to regulate the spacing of the rivets.
a]the first rivet is pressed
b]the rivet is then indexed over so the the first rivet is pushed up to the outside diameter of the small raised area of the anvil, then the second rivet is pressed and so on. Because the small raised portion is circular the sheet can move in either direction. When I work on an arc or a circle I have been following ink marks on the brass and do it freehand.
The next shot shows the anvil and the pressed rivets.
I did publish a very simple rivet press for styrene in and early Tome
I hope this helps.