Magnets...here's how they work...

I have magnetized one piece before this, the weapon on my heldrake.  I wanted to change up the weapon on my Terminator Lord so that I could run him with dual Lightning Claws, but I had already glued a combi-melta arm to him before I decided to do this.  With some careful pulling and prying, I broke the super glue bond and began the modification.

I used a small hand drill to start the holes in the arms and the shoulder. Then I cut and slowly made the hole bigger until the magnet could fit without sticking out.  I put a little bit of green stuff behind the magnets with a fair amount of super glue to hold it all in place.  I think it turned out pretty well.  I plan on doing the left arm as well so that I can change out the primary Lightning Claw for Power Weapons or a Power Fist if needed.

First time trying this, but here is a video of switching arms:

And the usual pictures...see if you can spot my assistant who always shows up when I am working on Warhammer models.