(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 counter- clockwise 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 4-9Continue Reading