Originally Posted by Reynolds 531

Its brazed on mild steel.

Dont try to weld it, it will only make it worse.

Option 1 to just go ride: Cable clamp onto frame.

Option 2 to fix pretty well: Cut half a circle, and weld internally with mini-mig (aka "zap") and then carefully clean inside and specifically fit the cable housing.

Option 3 restoration: Carefully remove existing stop. Braze on new one from Nova Cycles (or similar). Rechrome frame.
------------------------------------------------
If it was me, I would machine on a lathe a cable stop replica of stainless steel, polish it, and then cut in half.

Then I would carefully "zap" mini-mig weld (hidden internally) to the existing cable stop ABOVE the brazed chrome stay. (this will prevent the existing braze from overheating)

There may be internal burrs (from the tack welds) by doing this, but they will be hidden by design. The intent is to be as non-intrusive as possible, to avoid any heat messing up the original braze or chrome.

Then, the cable housing could be sanded externally as appropriate to fit by the "burrs", and all repairs would be hidden. The color difference between polished stainless repair and 40 year old will be negligible.

------------------------------------

I just came up with another idea: The cable stop doesnt really need to be "split", so you could weld the same polished stainless repair circle along the top, externally. (this should be done with 0.024 stainless wire).
By doing this, you will avoid internal burrs, and can sand and polish the repair on the top.