I recently built a surface grinding attachment with a steel chuck (see picture below) and have been using it to clean up blades after heat treating. It works great, but the chuck magnetizes the blades. I have a demagnetizer on order, but I really wanted to demagnetize a blade today, so I experimented a bit and came up with a method that worked so well I thought I'd share it.
My chuck uses 60x10x5mm neodymium magnets that I inserted into the slots with alternating polarities, i.e., every other magnet is flipped. I am not entirely sure whether this increases or decreases the force of the chuck or not, but I found this article about pull force of side by side magnets that indicates that the alternating arrangement may increase the pull force. I don't really know how demagnetizers work, but I think they create a magnetic field of alternating polarity that leaves the steel demagnetized. So, I thought if I could pull the blade along the chuck without it getting stuck on the chuck, it might do the trick. I tested different spacer materials I found around the shop, and what worked best was a piece of cardboard that was around 1/8" thick, maybe a little bit thicker. I put the cardboard on the chuck and pulled the knife along the length of the chuck and it came away demagnetized. I tried this with several blades and it worked every time. It worked so well that I am wondering whether I'll even use the plate demagnetizer when it gets here.
My chuck uses 60x10x5mm neodymium magnets that I inserted into the slots with alternating polarities, i.e., every other magnet is flipped. I am not entirely sure whether this increases or decreases the force of the chuck or not, but I found this article about pull force of side by side magnets that indicates that the alternating arrangement may increase the pull force. I don't really know how demagnetizers work, but I think they create a magnetic field of alternating polarity that leaves the steel demagnetized. So, I thought if I could pull the blade along the chuck without it getting stuck on the chuck, it might do the trick. I tested different spacer materials I found around the shop, and what worked best was a piece of cardboard that was around 1/8" thick, maybe a little bit thicker. I put the cardboard on the chuck and pulled the knife along the length of the chuck and it came away demagnetized. I tried this with several blades and it worked every time. It worked so well that I am wondering whether I'll even use the plate demagnetizer when it gets here.