So you're sewing along on your 401A, minding your own business, and then out of the corner of your eye you notice something strange...
The stitch length selector is moving upwards.
All by itself.
And your stitches are getting shorter and shorter, and shorter...
Uh-oh, your sewing machine is POSSESSED!
Actually, no. There is a simple explanation and a simple fix.
Simply put, there's a nut inside the end of the machine beneath the hand-wheel and if it isn't tight enough then the stitch-length lever will "wander" as you sew. This is especially true if you're sewing heavy duty fabrics. The additional load on the machine causes the lever to wander.
The very early 401A's are particularly prone to this complaint. In fact, this issue prompted Singer to make a design modification early in the production run. It's a little thing but instantly noticeable when you look at an early model and a later model side by side:
401A - Serial Number 652703
401A - Serial Number 706946
The stitch-length selector plate on the earlier machine is completely flat at the bottom, while the later machine has a notch at the longest stitch length. This indentation allows you to "lock" in the stitch lever at the longest stitch length. Which means that the lever cannot move when set at the longest stitch. Great for sewing heavy fabrics.
So what if you have one of the machines with the flat plate? Or what if your lever wanders when set at a shorter stitch length? What can you do about it?
The adjustment is simple, but first the hand-wheel must be removed. You'll need a medium-size flat screwdriver and 9/16" socket wrench or large screwdriver:
Use the medium-size screwdriver to remove the small screw in the center of the hand-wheel.
Next remove the chrome center section of the hand-wheel by unscrewing it in a counter-clockwise motion until it comes off.
Slide the washer off of the center post. Then grasp the hand-wheel in both hands and pull toward you. Look for the recessed hexagonal nut directly beneath the hand-wheel location.
Tighten the nut using the large screwdriver or socket wrench. (The socket wrench provides more leverage and makes for an easier adjustment, but take care not to apply too much force as you can break the head off the nut.) Usually 1/8th of a turn to the right (clockwise) is sufficient to tighten the lever action, but it may take as much as 1/4 of a turn. Raise and lower the stitch-length lever to be sure. You should feel an increase in resistance in the lever as the nut is tightened.
Reverse the steps to replace the hand-wheel.
There, you're done!
Amazing how a simple adjustment can so greatly impact the operation of your machine!
Happy Sewing! Barbara
OldSewinGear...dedicated to helping you get the most out of your old sewing gear.
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.