Thanks. Drilled out to 1.3mm then with a 3mm drill bit, very lightly, by hand, chamfer the edges of the lug holes. Soften with a fine grade sandpaper (2000), then polish.
Just finished - 5513 on NATO:
Cartel, shaped CGs, softened case
Drilled lug holes, 1.2mm
Athaya 702 crown and tube
Clark bezel and T19 Crystal
Yuki dial and pearl
Tudor ETA handset
ETA 2846
Phoenix G10 NATO