How do I adjust the timing (synchronization) of my Union Special 51100N machine?

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Timing Adjustment - Needle/Looper Synchronization

The timing, or needle-looper synchronization, is crucial for the proper functioning of your Union Special 51100N. Here are the essential points:

Critical Tolerance

The maximum allowable variation between the needle and the looper is 0.005 inch (0.127 mm). Beyond this, you risk missed stitches or needle breakage.

Hook Position

When the needle rises about 1/16 inch, the tip of the hook should meet the needle slightly above the eye. The space between the tip of the hook and the needle should be about half the width of the thread.

Looper Drive Lever Adjustment

If your synchronization is off:

Loosen the screw (E) of the looper drive lever
Pull the adjustment screw (F) towards you (towards the operator), then tighten
Check the synchronization
If the timing is too low: lightly tap the screw (F) away from you, tighten, and recheck
If the needle-looper distance increases when the handwheel turns in the operating direction: slightly move the rocker shaft of the looper drive lever backward

Recommended Tools

For optimal precision, use a synchronization gauge set (model TT34) which will allow you to accurately measure spacings and positions.

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