To wind a bobbin you first turn the "stop-motion-wheel" to the left releasing the hand wheel to spin freely without all the rest of the machine continuing to turn. But, in the real world........
The hand wheel and the bushing it turns on is rarely oiled. The hand wheel needs only a drop of oil at the gap of the hand wheel and the flange of the bushing if it had been oiled routinely. If it hasn't been oiled since the machine left the Singer factory the hand wheel will need to be removed, the bearing surfaces cleaned, oiled and restored to be correct.
But there is a deeper problem that may be causing your machine to run-on. I have in the past done all the cleaning and oiling thing and some machines will still run-on. These machines have gotten perfectly "run-in". The gears and bearings and all that kinda' stuff have worked with each other long enough that the wearing-in of these parts has made these parts fit each other perfectly. Every thing turns with seemingly no resistance except that which is felt because the motor is being turned by its' connection through the drive belt.
If you suspect you are having a problem this way remove the motor drive belt and turn the machine using the hand wheel. If you can't really discern any resistance consider this cure.
Roll your machine over onto its' back on to a padded surface. The machine's hand wheel should be to the right for this conversation while you are looking at the drip pan on the machines' bottom. Exciting isn't it? Remove that drip pan and have a look within. There is a gear at one right end of the silver colored lower high-speed shaft that has the chrome hook assembly (where you snap the bobbin carrier with its' bobbin into) at the left end of the silver shaft. (The white/green model 221's do not have gears so use the rubber t gimbler drive belt hub for your point of reference). The shaft goes through the gear (hub) and into a "block" that is part of the machines' base casting. In the middle of the block is a screw, a set-screw. The bushing that supports the gear end of the shaft is held in place (kept from moving) within this block by this set-screw. If you over-tighten this set-screw CAREFULLY the tightening will deform the bushing slightly and induce some resistance to the turning of the lower shaft and therefore the whole machine.
This set-screw hasn't been turned in sixty years. Loosen the screw before you tighten it. Press firmly into the set screw and use a quality screw-driver that fits the screw slot properly. Ladies, you might need some help with this, after sixty years of waiting for a little attention the screw will not like to turn at first and will start to turn with a pop. Loosen the screw before you try to tighten the screw and maybe even remove and oil the screw or its' hole. When you tighten the screw keep turning/testing the hand wheel to feel for added resistance. As we tighten the screw we will be turning the screw tighter than is required to just hold the bushing in place. I am asking you to tighten it just enough that the bushing distorts slightly and pinches the shaft inducing a resistance to the entire machines being able to turn. It will take some effort to turn the screw enough to make a change but the screw will only turn about 1/32th of a turn at most.
Tighten and test for resistance of the machine to turning. If things get a bit too tight, loosen the screw and the shaft will respond accordingly. We do not want a lot of resistance to the turning of the machine, but there must be some. Properly adjusted the machine will turn easily but you can feel it turn rather than something that seems almost sloppy loose.
Source: Dave's Blog