Joined: Jan 2010
Posts: 9,831
Likes: 1,809
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
The caps covering the arm bolts should be impacted around their periphery with a wood dowel, using a 2# hammer. That will break the threads free, so then easily spun out.
I bought a 24" wheel Hamilton triathlon frame (24" wheels were a thing in the 80's) that appeared to have been submerged for some time, probably in a basement that flooded. The rust is bad inside and out.
How thin that the tubing is butted might be a factor, but the lugs are comparatively thick.