[David G4EBT]

As has been said, the original 'cement' used to secure bases and top caps was a mixture of shellac and wood flour. It can be softened and removed by immersion in methylated spirits (known outside the UK as 'de-natured alcohol'). As a hobbyist woodturner I have lots of wood flour and shellac available so I did try it, if only for authenticity, but wasn't much impressed with the results. At the time, my main requirement was in converting EBL1 side-contact valves to EBL31 octal valves, which entailed changing the base and also changing the top cap from 3/8" to 1/4".

I ended up using 'PLASTIC PADDING SUPER STEEL EPOXY-WELD' which has proved entirely satisfactory. It has heat resistant properties well beyond what we're looking for.

This is from the maker's spec sheet:

SUPER STEEL is a dark-grey coloured, metal-filled, two-component adhesive which sets like steel and is suitable for metal, wood, china, stone, glass and leather. It hardens in 5 mins and cures in 10 mins. Max. temp 315°C (<100 continuous). Contains 54g/l solvent. Suitable for metal, wood, china, stone, glass and leather Not for soft plastic and Polypropylene.

In addition to securing valve bases and top caps, I use it for all sorts of radio related tasks - Bakelite cabinet repairs, sealing the ends of 're-stuffed' capacitors and filling unwanted holes is die-cast aluminium project boxes. Despite the claim that it's 'metal filled', and its title 'Super Steel', it isn't conductive.

Some pics below:

Pic 1: EBL1 valve converted to EBL31 (new Octal base and 1/4" top cap secured with Super Steel).
Pic 2: A strip of Super Steel applied to glass, subjected to 1,000V insulation test. ('1' on the display = no conduction).
Pic 3: End view of a re-stuffed 1935 vintage cap.
Pic 4, several re-stuff caps.

It sets rock hard, can be drilled, sanded and filed.

Hope that's of interest.