A few companies sell a magnetic clamp for creating strong magnetic fields. Although the clamps are sturdy and versitile, they are expensive. Often very expensive. I decided to make my own.
I used a Jorgensen wood clamp. The clamps are very strong, and the threaded screw rods allow for very precise adjustment. The magnets are from K&J Magnetics and are 1" x 2" x 0.5" N42 rare earth magnet with (and this is the good thing) counter sunk screws holes. Excellent. Mine took a #10 screw and I used non-magnetic stainless steel, though magnetic steel would have probably been okay. (They are out of stock on this particular magnet, but they expect more and others would work.)
The key is to drill holes in the wooden handle first, then drive in the screws.
The idea was to make a pendulum that would show eddy currents. The bar is made of aluminum an 1/8 inch thick and the plates are made from 6 x 12 x 1/8 inch aluminum as well. I cut the slots on a miter saw but I don't recommend that as it was very dangerous, although it works with a carbide blade. I tried a bunch of ways of attaching the plate to the blade, but opted for the clamp which can be changed out the quickest. All the metal was obtained from Online Metals. They cut to order and for cheap.