Duerkopp Adler 506 Service Instructions Manual page 19

Worm wheel set
For conversion to a curve disk 4 of a different stitch number range the
appropriate worm wheel set must also be mounted. A worm wheel set
consists of a worm driver 2 and a worm 3.
2 3
Gear reducer
Through installation of the gear reducer 6 with the intermediate gear 5
the number of stitches per curve disk revolution is doubled
(multiplication ratio 1:2).
Without gear reducer:
With gear reducer:
5
4
42, 58 and 72 stitches per curve disk
revolution (depending on the worm wheel set)
84, 116 and 144 stitches per curve disk
revolution (depending on the worm wheel set)
6
19