Feickert Protractor - anyone use one?

mohawk, I've used a Dennesen for years.  It predates the Feickert and works on the same principles but is not as versatile.  It has been out of production for years and was offered in both metal (which I have) and plastic versions (lower cost).  It does have a "divot" to precisely locate the stylus tip.  Used examples do appear from time to time.

https://images.search.yahoo.com/search/images;_ylt=A0SO8zY5DoJZi_4AMztXNyoA;_ylu=X3oDMTEycmVrcm81BGN...

While I've never used a Feickert I expect it has the same limitation as my Dennesen.  They really only work with arms which provide some means of identifying the precise pivot point for the arm.  That can be a bearing set screw, damping fluid well, etc.  If you are simply trying to estimate location of the pivot point, whether by eye or by measuring, I don't believe you can have the necessary accuracy for something as precise as the stylus alignment. 

Good point Lew.

Actually I've utilized my Dennesen to precisely locate the spot to drill to mount an arm.  With the P2S dimension given by the arm manufacturer and a steel metric ruler I set that distance on the Dennesen.  Then placing the alignment plate on the spindle I can swing the device to identify the arc on which the arm should be located.  From that I chose a position on that arc which best accommodates the arm and mark that point to drill.

All this seems obvious if anyone owns a Dennesen or similar alignment tool, but those considering buying one may not realize this extra benefit of this type of alignment device.  

Lew, another method which I've done over the years is to create a template out of sturdy stock such as a file folder.  I have basic drafting skills so can lay out a line with the exact center hole for the spindle, the P2S distance from that to arm pivot point, and then mark that with a vertical needle.  Rather than attempt to cut out a circle for the spindle I found a simple X cut with an X-acto allows the template to be fitted over the spindle.  Anyway, it worked for me.

My above post assumes the arm does not have a factory mounting template.  Buying used arms typically eliminates that convenience.