I did exactly the same thing with some toolholders. The problem was cured with a steel shim and JB Weld. There were two problems, P1,clamping the shim in place, required a small bit of mylar as a release agent, to ensure that everything wasn't stuck together forever, and P2 leaving the toolpost and toolholder clamped up for 24 hours whilst the epoxy cured.
Best of luck,
cheers
Bill