Houston, we have a problem.
After slitting, removing the burrs, and cleaning it up, it appears to have sprung about 0.002" closed. So now the bore is 0.998" and a 1" tool won't fit. Of course in the Uddelholm brochure for this metal says to stress relieve it after rough machining at 985°F for 2 hours.
So now to decide my options. Maybe just enlarge the bore? But the OD of the bushing is now 0.002" less than 40mm for the boring bar holder. But it probably has enough clamping movement for it to still grip the bushing.