Note:

1. After publication of this article I received a note from Scott Grandstaff clarifying some issue of casting methods and pointing to some mistakes on my part.  Hence, the casting issues of the transitional frame described on page 3 are edited.  Thank you Scott!  The question remains on differences between casting of frames for No.2-1938 and improved casting of No.2-Transitional frames.  How was this improvement achieved?

2. Another reader pointed me to the study by George Langford in which George mentioned the existence of two different metal frames for No.2A drill.  Indeed, the description of the No.2 Type A in George's study indicates that. Thank you George!

However, George suggests that ZAMAK castings made by Millers falls "to their everlasting credit, none of these die-cast frames has fallen into pieces. I haven't found any broken frames made either from malleable iron or this pot metal."  My experience, described in the above articles, is different.  A dozen or so broken frames are here and can't be ignored.