To remove and satin polish internal tig welded corners requires a sequence of belts with a Dynafile or Beltit type powerfile machine.
A light tig weld with little build up:
Step 1: Remove weld with FX87 P80 grit belts
Step 2: Blend the finish with VT FE2 medium surface conditioning belts (240 grit finish)
A heavier tig weld with greater build up:
Step 1: Remove weld with FX87 P60 grit belts
Step 2: Refine the grind lines with the P120 grit TZ59 belts
Step 3: Blend the finish with VT FE2 medium surface conditioning belts (240 grit finish)