So the sliding cover to the bobbin compartment on your 401A has popped off and you can't get it to stay on. So you take a closer look and discover that the spring that holds it in place has broken.
Singer 401A bobbin cover plate
On closer inspection you can see the screw that holds the spring in place. There's just one problem...you can't get to it... The head of the screw is blocked by the hook and bobbin case. So how do you get to it?
The solution is simple...if you know where to look. The first step is to tilt the machine back and look under the lip of the sewing platform directly below the bobbin compartment.
Slide plate spring with attaching screw.
Beneath the lip you'll see what looks like the end of a screw with a slot in it. It looks like the tip of a screw because that's what it is. In fact, it's the end of the screw that holds the spring in place. You can't access the head of the screw down inside the bobbin compartment, but you can unscrew it from the opposite end on the outside of the machine.
Attaching screw for bobbin cover plate.
Using a standard screwdriver, turn the screw clockwise to loosen. (This is opposite of the usual "Lefty loosey, righty tighty" principle because you're working on the tip of the screw, not the head of the screw.)
Once the screw is loose, remove the spring by sliding to the right, tilting slightly, and lifting out.
Remove spring by sliding to right and tilting slightly.
Replace the broken spring and reverse the steps to tighten the screw. Once the spring is fixed in place, reattach the sliding plate. Position the plate behind the spring and use a small screwdriver to lift the wings of the spring into the grooves of the slide plate. Slide plate towards you to snap into place.
OldSewinGear is the collaborative effort of retired repairman Gary and daughter Barbara. We love old sewing gear and enjoy sharing what we've learned in our vintage sewing machine adventures. We are located in Roseburg, Oregon.