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David Trumble
Dec 07, 2017
In Timing
Timing refers to the consistent formation of stitches achieved when the Needle bar, Feed dogs, and Hook Assembly all work together precisely, If the stitches form, the machine is in time. If stitches skip or fail to form consistently, they machine is out of time. There no single adjustment to make this happen. The needle bar, feed dogs, and hook must all be adjusted to produce consistent stitches.
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David Trumble
Dec 07, 2017
In Sewing Machines
Lock Stitch Formation: Thread from the upper thread source is drawn down through the material with a needle. The needle reaches its farthest down position and begins to rise again. After rising about 2.8mm, a loop forms on the back of the needle at “loop lift”. At “loop lift’ the hook moves behind the needle, picks up the thread, and wraps the thread around the bobbin. The needle continues to rise pulling the threads taught forming a thread knot inside the fabric.
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David Trumble
Dec 07, 2017
In Sewing Machines
The thread line from both upper and lower thread sources has built-in resistance from tension discs, tension springs, thread guides, etc. When the resistance from the top and bottom thread sources equalize, the thread knot forms inside the fabric with threads lying smothering on top and bottom of the seam and with no excess thread above or beneath the fabric. This is called balanced tensions. Unbalanced tensions result when one thread source pulls harder than the other. The source that pulls the hardest produces excess thread on that side of the fabric. If excess thread is under the fabric, the lower thread source is pulling harder than the upper thread source. If excess thread is on top of the seam, the upper thread is pulling harder than the lower. Adjust the resistance to re-balance them by adjusting tension discs, tension springs, and by eliminating any sticky, rough, burrs, or otherwise interfering surfaces affecting the tensions. Note: the numbers on the upper tension dial are useful for users. Therefore, ignore the dial until balance is re-established then reset the dial to its user settings.
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David Trumble

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