Hi Mike,
The problem could be related to cutter run-out (not running concentrically) which results in the tip spinning off-center and creating the flat region where there should be a sharp line.
If there is a small flat on the tip of the cutter it's best to define it as an Engraving Tool in the Tool Database, adding the approximate Flat Tip Diameter. Remember to specify the half angle - 45 degrees for a 90 VBit.
Another thing to be aware of is the results you get if the cutter angle is out by a few degrees. The images below show the results of programming a toolpath with for a 90 degree VBit but actually cutting the job with 80 and 100 cutter degree cutters.
Let us know how you get on with the tests,
Tony |