[philso]

Hello Matt

Perhaps soaking in solvent is the way to go even though it would be much slower.

I just read a datasheet for some neodydmium magnets last night and they indicated the magnets would start to lose magnetic strength above a surprisingly low temperature. I don't recall the exact number but it was something like 80C. I am sure the industrial heat gun gets hotter than that since we were charring the solid maple workbench with the blast. Unfortunately, I don't recall which manufacturer posted this data (it was pretty late).

We also noticed that the pulling force of the magnets that we measured seem to decrease to a fraction after removal from the backing plates. This observation applied to the ones we heated as well as the ones we sheared off. We suspect that the backing plates are some sort of high-permeability steel and they concentrate the magnetic flux. They look rather thick for the mechanical stresses involved.

Another strange phenomenon we noticed is that the magnets seem to be magnetized in zones along the arc. The pair of magnets from one hard drive would stack nicely but magnets from another (different brand/model) would only stack with an offset. In the past, I had noticed this same effect with strips of flexible magnets.

Since we could not get the pulling force we needed with the magnets from the dead hard drives we now have some on order from an online supplier.