Vacuum Fil shaft screw

[Sagebrush64]

I recently picked up as it turns out a very nice black reticulated barreled Vacuum Fil pen. I've got everything disassembled except that darn 2 part brass screw on the end of the shaft.
Is there a trick to getting the bugger off?? I've tried heat, soaking, heat, soaking and a bit of muscle all with no luck. I don't want to damage anything.
TIA

Update: I finally got the silly bugger off and cleaning proceeded smoothly. A new gasket and ink is easily sucked into the barrel. The packing is a bit weak though and will need replacing at some point in the future. Still all in all, a very nice little pen that is quite at home with it's brother and family!