Minecraft custom item texture - experiencing ghosting

I am attempting to create some HD textures for Minecraft (currently version 1.8.1). I succeeded in getting the image to load in the game, but it doesn't look right. It appears that the game is trying to create a thickness for the item (this example is an iron sword). I used the same resolution for a birch log block that turned out great, of course it's a square item so I can imagine that trying to create thickness of a hand-held item is more difficult.

Does anyone have any suggestions on how to improve/remove this artifact for items?

Thanks.

Edit: Here is the texture I used: