It is easier to thread a vintage sewing machine than a new machine. On a vintage machine nothing is hidden--all the hooks and the tension knob are on the outside of the machine. This basic design remained the same well into the 1950s and 1960s. The same basic steps are used to thread most older machines.
Place a spool of thread on the spindle and an empty bobbin on the bobbin winding spool. Pull the thread to the left and wrap it around the metal hook on the top of the machine, or around the bobbin thread tension button if the machine is equipped with one. The bobbin thread tension will be a round flat knob on top of the machine. Pull the thread to the right and wrap it around the bobbin several times.
Disengage the hand wheel to prevent the needle from rising and falling as you wind the bobbin. You can usually do this by loosening the knob in the center of the wheel. This may not be possible on some older model machines.
Run the machine until the bobbin is wound. Hold the loose end of the thread until the thread is firmly wrapped and will not come loose. Cut the thread and remove the bobbin. Locate the bobbin case in the bobbin compartment under the pressure foot. Lift the metal latch on the bobbin case and pull the case out. Place the bobbin in the bobbin case, and replace the case in the bobbin compartment. Your bobbin compartment may be behind a door, and may open horizontally or vertically.
Re-tighten the hand wheel if you disengaged it previously. Turn the hand wheel until the needle is at its highest point.
Wrap the thread around the hook again and bring it down in front of the machine, around the tension knob and up again. Be sure the thread goes between the two metal discs behind the tension knob.
Thread the thread through the take-up lever from right to left. The take-up lever is the metal bar with a hole located over the needle. It goes up and down when you turn the hand wheel. Bring the thread through any hooks located between the take-up lever and the needle, going from the top down. There will always be a hook or loop on the needle holder bar just above the needle. Sometimes there will be one above that on the body of the machine.
Thread the needle. If the last hook is on the front of the needle holder bar, thread the needle from front to back. If it is on the side of the bar, thread the needle from that side of the bar to the other.
Hold the end of the thread as you turn the hand wheel to lower and raise the needle one time. This will bring up a loop of bobbin thread. Pull this loop until the end of the thread comes out. Pull both threads to the back.
Some very old machines will not have a bobbin winder, but had a separate bobbin winding device.
You may have to push the bobbin spindle to one side or hold down a button to wind the bobbin.
If your machine will not wind bobbins you may be able to find pre-wound bobbins to fit your machine or you may wind the bobbins by hand.