1. The same effective modification could also be made without replacing the original bellows. Rather than machining a new central section, a similar piece may be placed between the existing central section and the lower housing. This sector need only be sufficiently high to accommodate a pumping port tube of the desired size and be machined with O-ring grooves on its upper and lower faces. The center shaft may then be lengthened the appropriate amount by an extension piece which threads into the end of the existing shaft. The lower face of the existing central section must also be polished smooth for the O-ring seal.
2. Brazing Manual, American Welding Society. Committee on Brazing and Soldering (Reinhold, New York, 1963), p. 133.