The sliding buttonhole foot is one type of buttonhole foot. It came with my Pfaff 1475 (on right) I obtained late 1991 and with my Riccar 808E obtained late 1978. (on left)
The red arrow indicates where the buttonhole will begin. As you stitch the slider moves and the calibrated lines will help determine the buttonhole length.
How is this buttonhole length determined? Many times I've read to put a tape measure around the button. What? A better idea would be to put a string around the button, then measure the string.
I have a different way of doing it which I have been using since the early 80s.
An old piece of scrap fabric was used upon which I stitched buttonhole to the lengths of each red mark and the half red ones.
It doesn't have to be anything fancy. This was done on scrap fabric and buttonholes were mainly for length, not beauty. After all,, no one else was going to see this but me. Ha!
Just slip the button through the buttonholes until the perfect size is found, then stitch the buttonhole to that length.
The Pfaff 1475 has fully automatic as well as semi-automatic buttonholes. To determine which length of buttonhole to program in, use the strip for the button. You will need to know how the red marks translate to metric as that is how most Europeon machines are programmed. For example, notch 4 1/2 is 20 mm; notch 6 1/2 is 28 mm.
When using semi-automatic buttonholes on the Pfaff 1475 use 150 flashing. When the first side reaches the length you want, proceed with the rest of the buttonhole.
For more accuracy and control I tend to use the semi-automatic mode as opposed to the fully automatic ones. For years I've said that I should make a similar strip for my Pfaff 1475, but there is really no need as the red marks are the same on both buttonhole feet.
As usual, click on the pictures to enlarge.