You need to get holders that use postive rake, take a look at
http://www.thegallos.com/carbide.htm for some good background on this.

I like to get cutting tools that all use the same insert, and an insert
that's widely available and inexpensive.
I have well made cutting tools from Valenite that use the popular TPG-221
and 222 inserts.
I bought them from MSC so if you dig around in their catalog you'll find
them.
APT makes some additional tooling such as boring bars that also use these
TPG inserts.

I like the Valenite tools because the clamping system is sturdy and well
made and replacement parts are easily available.

I really dislike the cheapo tools from Enco and others that use the inserts
that have a small screw through the middle holding them, they are
troublesome and I would stay away from them.

The link above mentions tools from Microdex that also sound pretty good.

Good luck-

Paul T.