Pfaff 2170 - Manual (Page 143)

Embr
oidery
5:46
Threads
The thickness of the thread is represented by a
number: the lower the number, the thicker the
thread. Most embroideries are designed for 40 wt
thread.
Rayon thread
Rayon thread is a soft and durable thread with a
shine and is often used when embroidering.
Metallic threads
Special threads like metallic threads are more fragile
than rayon embroidery thread. To avoid thread
breakage you should lower the speed and use the
vertical spool pin. Place the thread on a spool holder
using a felt pad and use a metallic needle.
Bobbin thread
When embroidering you should use a special bobbin
thread. The bobbin thread is thinner than normal
sewing thread and prevents embroidery build-ups
on the wrong side.