Our company purchased a nice CNC Lathe a few months ago and we have slowly been accumulating tooling for it. In an attempt to save a little money in the short term, I purchased a Dorian/Newcomer slot-grip style grooving/cutoff blade and toolholder. It works ok for the minimal amount of shallow grooving that we use it for. The problems arise when we try to cut off anything more than 3/4" in diameter.

On anything that size or larger, the tool leaves a significant taper on the cutoff surface. The back side of the workpiece after being cutoff always has a dome shape, while the remaining stock has a less-noticeable concave shape. We have tried re-positioning the bar, indicating the blade to near-zero, and even shimming the tool-holder to way over compensate for the taper and STILL it will not cut correctly. I am at my wits end with this thing. I know other people are using them successfully so what is the logical procedure for making this thing work?

Any tips, hints or suggestions would be greatly appreciated! Thanks ahead of time...