ADJUSTMENTS

For the sewing machine to operate smoothly and to make a proper locking stitch, you must make some minor adjustments. Even though the machine is in time, a single part that is out of adjustment can cause the sewing machine to skip stitches, break thread, fail to feed the material, or make loose stitches.

1. Adjusting the bobbin-case opener

As the hook rotates clockwise, friction on the bobbin-case opener causes the position lug

Figure 4-10B.\Presser-lifting eccentric.

(figure 4-9 [A]) to press against the back of its opening. The bobbin-case opener moves the bobbin case counterclockwise to allow the thread to pass around the bobbin-case-opener lug. If the opener is adjusted too tight, damage to many parts may occur; and if the opener is not set tight enough, extreme upper thread tension may be necessary to lock the stitch properly. Adjusting the bobbin-case opener is accomplished as follows:

a. Turn the balance wheel toward the operator until the bobbin-case-opener lever (figure 4-9 [C]) moves as far to the right as possible.

b. If the bobbin-case opener (figure 4-9 [D]) has been removed, reinstall it at this time. Do not tighten the adjusting screw (figure 4-9 [E]) at this time.

c. Place two thicknesses of paper, as a gauge, between the tip of the bobbin-case opener and its projection on the bobbin case.

d. Move the bobbin-case opener right or left as necessary to cause the bobbin case to move as far to the right as possible without binding.

e. Tighten the bobbin-case-opener adjusting screw.

f. Turn the balance wheel toward the operator and observe the operation of the bobbin case and its opener. Ensure no binds are present and that the bobbin case is pulled counterclockwise as far as possible with each rotation of the hook.

2. Adjusting the total relative lift of the alternating pressers

The total relative lift of the alternating pressers referred to here is that the feet lift one-half inch at total lift. Maximum lift of the alternating pressers is set to sew on heavier goods. There are two types of adjustments, and either type may be found on a given machine. The first type of alternating presser (figure 4-10A) is usually found on earlier sewing machines, while the second type of alternating presser (figure 4-10B) seems to be in current manufacture.

a. Adjusting the first type of alternating presser is accomplished as follows:

(1) Turn the balance wheel toward the operator until the presser-lifting eccentric lock screw (figure 4-10A [A]) is visible inside the opening at the back of the arm of the machine. (See figure 4-11 [A], table 4-3, foldout at end of this chapter.)

NOTE: Figure 4-10A shows two setscrews (B). They are used to hold the presser-lifting eccentric in place on the feed-driving rockshaft. The adjusting screw is not visible in this figure.

(2) Loosen the lock screw and turn the balance wheel until the adjusting screw is visible in the opening in the back of the arm. (See figure 4-11 [A].)

(3) Turn the adjusting screw counterclockwise to obtain maximum total lift of the pressers.

(4) Turn the balance wheel toward the operator until the lock screw is visible in the opening in the back of the arm and retighten the lock screw.

b. Adjusting the second type of alternating presser is accomplished as follows:

(1) Loosen the presser-lifting eccentric adjusting wing nut (figure 4-10B [A]).

(2) Move the assembly up to decrease the lift or down to increase the total lift of the alternating pressers.

(3) Tighten the wing nut.

3. Adjusting the relative lift of the alternating pressers

The alternating presser feet should each lift to approximately the same height. Do not confuse relative lift with total lift. Here we are adjusting the presser feet to lift to approximately the same height. Adjusting the relative lift of the alternating pressers is accomplished as follows:

a. Turn the balance wheel toward the operator and observe the action of the alternating pressers. If they do not lift equally, proceed to step b.

b. Turn the balance wheel until the foot that lifts too high is just above the throat plate.

c. Loosen the presser-lifting link crank pinch screw (figure 4-11 [B]). The foot should snap down; if it does not, push it down.

d. Tighten the presser-lifting link crank pinch screw.

e. Repeat step a. If necessary repeat steps b through d until the feet lift to the same height.

4. Adjusting the lifting linkage of the alternating pressers

To set the lifting linkage, you must loosen the lifting crank pinch screw (figure 4-11 [B]) and the presser bar lifting bracket pinch screw (figure 4-11 ----[C]). Turn the balance wheel toward the operator until the feed dogs rise to meet the forward presser foot at the top of the throat plate. Press the presser bar lifting bracket down to the hand lifting lever (figure 4-11 [D]). Tighten the presser bar lifting bracket pinch screw (figure 4-11 [C]) and the lifting crank pinch screw \ (figure 4-11 [B]).

5. Adjusting the upper thread-tensionreleasing lever

The upper thread-tension release allows the goods to be removed without the needle thread breaking.

a. Lift the presser-lifting lever and observe the thread tension disc. It should separate to release the thread. If not, proceed as follows:

b. Remove the thread controller assembly from the machine as follows:

(1) Remove the thread controller assembly retaining screw (figure 4-6 [1]). (2) Loosen the thread controller stud setscrew (figure 4-6 [J]). (3) Pull the thread controller assembly away from the machine.

c. Bend the thread releasing lever (figure 4-12 [B]) away from the thread controller assembly to increase the amount of the release and toward the plate to decrease the tension as needed.

d. Reattach the assembly to the machine and observe the operation. Repeat steps a through d if necessary.

6. Setting the feed indicator disc

Loosen the setscrew in the feed indicator disc (figure 4-1 [E]) so that it spins on the arm shaft. Depress the feed indicator plunger and turn the balance wheel toward you until it drops; keep turning the balance wheel toward you until it stops. The feed-driving eccentric is now set at 3 1/2 SPI.

NOTE: With the plunger engaged, turning the balance wheel toward you decreases the SPI, and turning the balance wheel away from you increases the SPI.

The ideal setting for the indicator disc on the sewing machine is 8 SPI. You accomplish this setting by engaging the plunger and turning the balance wheel approximately one-fourth of a turn away from you. Release the plunger, make several inches of stitches on a piece of paper, and count the total number of stitches per inch. If you are sewing 8 I, depress the plunger and slow/y turn the balance wheel toward the operator until the plunger drops. l Stop . . Release the plunger and the balance wheel. 

. Now turn the feed indicator disc (figure

4-1 [E]) on the arm shaft until 8 shows in the window on the uprise of your machine. . Tighten the setscrew in the fee d indicator disc.

7. Setting the thread controller spring

The thread controller spring prevents the needle from piercing the thread. It takes the slack out of the needle thread until the point of the needle enters the material.

To properly set the tension on the thread controller spring, you must first loosen the thread controller stud setscrew on the tension stud (figure 4-6 [J]). Turn the tension stud counterclockwise for more tension or clockwise for less tension.

A properly adjusted controller spring rests on the thread controller spring stop as the point of the needle enters the material. This action releases all tension on the needle thread.

8. Setting the controller spring stop

You may have to make an adjustment to the controller spring stop to allow the thread controller spring to operate properly. This is a very simple adjustment. By loosening the tension stud screw, shown in figure 4-6 (I), you raise the stop for less action or lower it for more action.

9. Adjusting the thread tension

The thread tension will be the last adjustment required. In most cases, you can make any adjustment required by turning the thumb nut (figure 4-12 [A]) on the needle thread tension disc.

If the stitch is locking on top of the material, turn the nut counterclockwise. This

will loosen the upper thread tension causing the bobbin tension to draw the stitch into the material. A clockwise turn will tighten the upper thread, thus drawing up any stitch that may be locking below the material.

If you cannot correct the tension by adjusting the thread tension disc, adjust the bobbin tension. To do this, tighten or loosen the small screw nearest the center of the spring. This completes all the necessary timing and adjusting on the 111 W 155 sewing machine. If you still have a problem, refer to the troubleshooting portion of this chapter.

TROUBLESHOOTING

While making adjustments or timing the sewing machine, you may overlook a step or a faulty part. The troubleshooting chart (table 4-4) will help you locate and correct most problems.

If the sewing machine is binding (hard to turn), you can locate the problem easily. First, check the feeding action; then set the machine on zero feed and remove the throat plate. Turn the machine by hand. If the bind is still present, remove the arm shaft connection belt. If the bind is located in the hook-driving shaft, the machine will turn freely. Turn the balance wheel by hand. If the bind is located in the arm shaft, the bind will still be present.