Having ditched the electromagnet idea, I now need to find (and find out how to find) the magnet I need.

The target is something like a 1/2 or 5/8 inch hex nut, either galvanized or SS, in the middle of a ball of clay about 2 inches in diameter. This will be sitting on top of about 1 1/2 inches of wood. And figure about 1/2 inch of air space. No other ferrous metal in between.

If everything between the magnet and the load is non-magnetic or non-ferrous, does it really matter if it's wood, plastic, fingers, or cloth?

I'd like to get something at the needed strength from say 3-5 inches, then have it drop off fairly quickly. Knowing that might not be possible, is it possible to attenuate or disperse the field to reduce the pull?

Ed

Setting up the magnet you want will be easy, any strong magnet should do the job for you to move the clay wrapped hex nut. Dispersing or dropping off the field will not be. The best thing for you to do from your description is to arrange for the magnet to drop away, straight down. Going straight will prevent a tell tale wobble of the load as the magnet moves away. If it moves even a little sideways it will wobble the load and tip the gaff.

Thanks for the info, Cliff. The magnet will likely be mounted to a cylinder about the diameter of an oatmeal carton, so the movement away from top dead center will be out and down. The cylinder will be mounted underneath my table top, close to the front edge, and the ball in a plastic cup. Wouldn't mind if the load was pulled forward enough to walk the cup off the table edge to fall - but it would be a bit of a bummer if the magnet sucked the ball back under the lip of the table?

Ed

I think you need to start experimenting. But don't use a SS nut because SS is not (usually) magnetic.

SS is not magnetic