I was in a local thrift shop a couple of weeks ago and saw a Singer 15-75. That was only the second one I had ever seen, so they are not that plentiful. The asking price was $75 and I have lots of straight stitchers, so I passed that one by but it reminded me that I have one tucked away that I got years ago.
The 15-75 has the same reverse sewing mechanism as the 15-91 and the 15-125 EXCEPT that it is belt driven, rather than direct gear driven like its sisters.
I didn't like the machine originally because it was too noisy but about a month ago I ran across the instructions for adjusting the shuttle cushion spring and I have been checking all my 15 Class machines for excess gap and correcting it.
The space between the tail of the cushion spring and the shuttle is supposed to be .010 - .014 inches, just wide enough to let thread pass through. Too narrow a gap and thread will get hung up; too wide a gap and the machine will be excessively noisy. Every machine I have checked has a much larger gap and this 15-75 had about .12 instead of the .012 it should have. Adjusting the spring quieted the machine right down and it is now a pleasure to sew on it.
