Opening limber holes

[mickelsen]

What is the best method for opening up limber holes in plastic models? I know you can grind them open from behind using a Dremel or something similar, but it is still fairly easy to grind too far and ruin the nice, neat hole. Is there a way to keep this from happening without having to just rely on your fingers not slipping? The older I get the less reliable my fingers are along such lines.
Thanks.

[He Who Shall Not Be Named]

Moto-tool with bits smaller than the hole you're working. Slow speed so you don't melt the plastic. Drag the bit around the perimeter of the hole you're making till you cut away the required material. Hand milling is what you're doing. Finish off the work with Jeweler's files, straight and riffler types.

David,

[mickelsen]

Okay. Just so I can learn and understand the process, why do I need to use a bit that is smaller than the hole that I'm working? I would think that a bit bigger than the hole would make it harder to slip down the side of the hole and ruin it. And what is a riffler filer?