The alternative is to use a pair of threaded reducers that will allow the use of standard English thread BB cups in the OS Chater Lea BB shell. I have done this with one of my Hetchins. I bought the reducers from the UK Tandem Clubs parts facility but I believe that they are actually made by George Longstaff and have perfect threads. These require careful machining due to the thinness of the steel left between the inside and outside threads. I guess that there are US producers too, or any good machine shop should be able to turn a pair up from drawings. Tony Beckett Wintery south coast of UK