Union Special XF500 Industrial Sewing Machine Maintenance Guide

Key adjustment steps

The following adjustments need to be made in order, otherwise they may affect the functionality of the relevant components. All measurements are in millimeters or inches, and torque values must be strictly followed.

3.1 Timing Feed to Needle

When the needle is inserted into the fabric, the feeding is still in progress and needs to be adjusted:

Remove the top cover, head cover, and other shielding components.

Rotate the handwheel until the needle bar connecting rod (A in Figure 2) is at the top dead center.

Loosen the four screws of the upper spindle sprocket (A in Figure 3) and secure the handwheel to prevent movement.

Rotate the lower spindle so that the plane of the feed crank counterweight (A in Figure 4) is perpendicular to the bottom of the machine and away from the operator.

Tighten the sprocket screw to a torque of 36 in lbs (41 cm/kg).

After adjustment, it is necessary to check the synchronization of the bending needle and the needle movement.

3.2 Synchronous bending needle and needle movement

Use specialized gauge 21227 R (single needle) or 21227 AD (double needle/three needle):

Remove the needle eye guard, thread picking cam, needle, presser foot, needle plate, bent needle, and feeding teeth.

Rotate the handwheel to the bottom dead center of the needle bar, with the bent needle seat at the rightmost end.

Install the gauge, insert the pin into the curved needle seat, and fix the indicator block on the machine head.

Turn the handwheel clockwise until the pin on the bent needle seat contacts the gauge plate, then gently tighten the screw of the needle rod connecting rod (A in Figure 6) and adjust the pointer of the indicator to "0".

Reverse the handwheel to make the pin contact the gauge plate again and observe the reading. Allowable deviation ± 1 scale. If the reading is off center, loosen the sprocket screw (K in Figure 5) and turn the handwheel clockwise; Turn counterclockwise if it is below. Repeatedly adjust until the pointer is within 1 scale for both forward and reverse rotation.

If there is no gauge, visual inspection can be used: turn the handwheel clockwise to align the curved needle tip with the left side of the right needle, and measure the distance from the needle hole to the bottom of the curved needle; Reverse the handwheel and measure again, adjusting the distance to be equal in both directions (as shown in Sketch D).

3.3 Needle bar alignment (double needle/three needle)

Install a new needle. When the needle bar connecting rod is at the top dead center, the top of the needle bar should be about 1 7/8 inches (47.6mm, temporary value) away from the top of the upper needle bar bushing. Gently tighten the screw (C in Figure 7).

Rotate the handwheel to ensure that the needle is in the center of the needle plate hole (Figure 8), adjust the rotation direction of the needle rod, and then tighten the screw according to the specified torque.

The needle plate can be fine tuned in four directions: loosen the three screws of the needle plate support (B in Figure 8) and the two screws of the positioning sleeve, and adjust by tightening the positioning sleeve first and then the support screw.

3.4 Bending needle setting (single needle)

Install a new needle (specified model size).

When the curved needle is at the far right end, the distance from the needle centerline to the curved needle tip should be 5/32 inch (4.0mm). Use the bending needle gauge 21225-5/32 to assist in adjustment: loosen the screw (A in Figure 9), turn screw B (clockwise increase, counterclockwise decrease), while bending the upper part of the needle seat to the left, and then lock it.

When the curved needle moves to the left behind the needle, the maximum gap between it and the needle is 0.002 inches (0.05mm), which can be adjusted by moving the curved needle seat back and forth.

3.5 Bending needle setting (double needle/three needle)

When the curved needle seat is at the far right end, the distance A from the center of the right needle to the tip of the right curved needle (Figure 10) is shown in the table. Loosen the stop ring screw (A in Figure 11), press down the release rod, bend the upper part of the needle seat to the left, and turn the adjustment screw D (increase the gauge clockwise, decrease counterclockwise), using the gauge as an aid.

Continue to bend the needle seat to the left, turn the stop ring clockwise to the end, and tighten screw A. Push up the release lever to lock it.

Adjust screw C with spring plunger (Figure 10) so that when the release rod is pressed down, the bent needle seat can spring open to the right (for easy threading), and lock when pushed back to the left. After locking, the release lever should be roughly aligned with the middle curved needle.

When the curved needle moves to the left behind the needle, the maximum gap between it and the needle is 0.002 inches, which can be adjusted by moving the curved needle seat back and forth.

3.6 Needle bar height

When the handwheel is turned clockwise to align the curved needle tip (A in Figure 12) with the left side of the needle (B), the top of the needle hole should be 1/64 inch (0.4mm) lower than the lower surface of the curved needle. Loosen screw C and adjust the needle bar by moving it up and down. Be careful not to disrupt the alignment of the needle bar.