listen carfully ok heres whatcha do buy a new one it ain't gunna fix itself unless u try some vbutter i recomend blue bonnet. lol but seriously try it.
Isaac Singer built the first commercially successful machine, which was electric powered instead of crank or pedal as all others had been.
Circular is one type. There are manual and hand crank knitting machines.
I do believe you have a 1921 model, but according to the singer website, for a machine that old, you would need to email or call them in order to get the model type.
i think it is a wheel and axle
A lever
There are many variable to determining the value - more detail is needed, year of manufacture, you can obtain that at the singer site - all you need is the serial number. These machines can be treadle, crank or electric. Condition of paint and decals? Is is a working machine? I have purchased them for as little as $5.00 (working electrical from 1932) and seen them as high as $100.00
a wheel and axle
The better machine shops can drill and tap the crank for you. Might be cheaper to buy a newer crank.
The lead singer has, Chester Bennington, has had small acting parts in Crank and Crank 2.
Singer made several variations of the 201, the most common in the US being the 201-2, with the internal motor. The 201-3 had an external belt driven motor, and was more commonly found in England and Canada. The Singer 201-1 was offered as a hand crank and yes, a treadle. So there is the detailed answer.
wheel and axle
a wheel and axle