hey i was looking into magnetizing my bases and putting magnets on my models the be able to switch weapons. Any one know what sizes i should use?
The smaller the magnets are, the harder it will be to work with them, but also they will show up less if they're smaller. For the switching of weapons, I recommend these fellas: You can find 'em here: http://www.rare-earth-magnets.com/SearchResult-CategoryID-34.html
The smaller the better for plastic arms, but asrodrig is right that they are very fiddly to work with. Especially when you should be aiming to make them completely flush with the plastic, and definitely not sticking out at all. But the further into the hole they are the less magnetising power there is. There is a topic with some good tips on rare earth magnets here: http://www.lustria-online.com/threads/rare-earth-magnets.951/
Great Tutorial on magnets and using them: http://www.warhammer-empire.com/theforum/index.php?topic=28730.msg395815#msg395815
Well all I can advice to when it comes to magnets and models is this link: http://boringmordheimblog.blogspot.com/search/label/Tutorials