Whorls are interchangeable on Flatiron, Ladybug, Matchless, and Sidekick wheels.

extra slow speed*—5-3/4″ diameter at the widest point of the whorl (measured across the back)
slow speed—4-1/4″ diameter at the widest point of the whorl
medium speed—3″ diameter at the widest point of the whorl
fast speed—2-1/4″ diameter at the widest point of the whorl
high speed**—1-7/8″ diameter at the widest point of the whorl
super high speed**—1-7/8″ diameter at the widest point of the whorl

*The extra slow whorl cannot be used on the Sidekick wheel.

**These whorls have the same diameter but the super high speed has deeper grooves. A high speed bobbin is required for spinning with high speed and super high speed whorls in double drive. (High speed bobbins are not required for Scotch tension mode.)

What whorls do I have?
Each new wheel comes with a medium and a fast speed whorl.

What whorl do I use?
It depends on your treadling rate, the fiber you’re spinning, and the amount of twist you want. There are no hard and fast rules about whorls. Choose a whorl that helps your wheel do as much of the work for you as possible. In general: select bigger whorls or ridges for longer or coarser the fiber or less twist in the yarn; select smaller whorls or ridges for shorter or finer the fiber or more twist in the yarn.

What do whorls do?
Whorls allow the bobbin to turn at a particular speed in relation to the revolutions of the wheel’s drive band. This relationship is given as a spinning ratio. A slower (bigger) whorl will slow down the bobbin and produce a yarn with less twist; a faster (smaller) whorl will speed up the bobbin and produce a yarn with more twist. Each Schacht whorl has a bigger and a smaller groove into which the drive band can sit, so each whorl has two possible spinning ratios.

	Flatiron	Ladybug	Matchless	Sidekick
Extra slow	4.6:1 and 5.2:1	3.2:1 and 3.6:1	4:1 and 4.5:1	N/A
Slow	6.8:1 and 8.5:1	4.7:1 and 5.5:1	6:1 and 7.5:1	4:1 and 4.8:1
Medium	10.4:1 and 12.4:1	6.5:1 and 8.0:1	9:1 and 10.5:1	5.7:1 and 6.8:1
Fast	15:1 and 17.4:1	9.0:1 and 10.5:1	12.6:1 and 15:1	8.0:1 and 9.0:1
High speed	20:1 and 25.2:1	11.5:1 and 14:1	17:1 and 20:1	10.0:1 and 12.0:1
Super high speed	21.2:1 and 26.1:1	12.0:1 and 14.5:1	18:1 and 21:1	11.0:1 and 13.0:1