Thanks for the help, after some off-line discussions with others who have actually done the correct waffle pattern and mushroom button riveting with a press, it is pretty much agreed that your press needs to be very solid and that it will NOT allow any side movement of the ram or the rivets will tilt every time. Also a special set of dies needs to be build for the press, with the waffle pattern on one side. Then being very careful with your alignment of the parts and rivets you will get the correct mushroom and waffle pattern. Unfortunately the custom die set is quite expensive to fabricate/machine and a good press is also tough to find. The testing that my vendor here did only required about 8 - 10 tons of pressure to mushroom the AMK rivets.