cleeds, Perhaps I misunderstand what you are trying to say in response to dang, but he is talking about turntables, not tonearms. In fact, there are at least 3 different "standards" for spindle diameter. As you might guess, it is critical for any protractor to fit snugly, with no "play", over the spindle. Conversely, the spindle diameter cannot exceed that of the hole in the protractor, else the protractor cannot be used. So, his question was not inappropriate to a discussion of protractors. In addition to owning an older Feickert, I also own a UNItractor. UNI was cleverly designed with interchangeable spindle holes; three are supplied. The one that fits my Lenco spindle perfectly does not fit my Japanese DDs and vice-versa. As to the Feickert, I can only say to Dang that I have used it with the Lenco and with at least one of the DD turntables I own; can't recall which. It seems to "fit" both but not so perfectly as does the UNI with a precisely chosen spindle adapter.
Also, although both the Feickert and the UNI are loosely based on the Dennesen, both are a bit better in that both allow for checking the alignment by supplying a second pattern, displaced toward the spindle, where the stylus tip and cantilever alignment is confirmed. (Maybe not a good verbal description, but if you own a Feickert you know what I mean.)
