How to Fix Thread Tension on a Juki DDL-8700

Introduction

This guide will fix the thread tension on a Juki DDL-8700 lockstitch industrial sewing machine.

When working on sewing projects, you often change the fabric and threads that you use. With this, the sewing machine tension must be adjusted before sewing. Without proper thread tension, loops and bundles of thread (bird nests) can be created, rendering the sewing machine almost unusable.

This guide will demonstrate how to fix thread tension issues, returning the machine to working order.

What you need

Step 1 How to Fix Thread Tension on a Juki DDL-8700

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Thread the machine.
Insert the bobbin case.

Edit

Step 2

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Sew a straight line on scrap fabric to test thread tension.
Be cautious when placing your fingers near the needle when working with the machine turned on.

Edit

Step 3

Check the fabric for loose thread tension.
Look out for loops of thread on the top and bottom of the fabric.
The bobbin case tension is too loose if loops are on the top of the fabric.
The upper thread tension is too loose if the loops are on the bottom of the fabric.

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Step 4

Take out the bobbin case.

Edit

Step 5

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Create a baseline thread tension for the bobbin case by tightening or loosening the screw on the bobbin case.
Thread should not easily unravel but can be pulled loosely.

Edit

Step 6

Reinsert the bobbin case into the machine.

Edit

Step 7

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Sew another straight line on the scrap fabric next to the previous line.

Edit

Step 8

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Check the front and back thread tension of the scrap fabric for loose stitches.

Edit

Step 9

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Adjust the upper thread tension.
If there are loose stitches on the top of the fabric, loosen the upper thread tension by turning the tension knob counterclockwise.
If there are loose stitches on the bottom of the fabric, tighten the upper thread tension by turning the tension knob clockwise.

Edit

Step 10

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Check the thread tension by sewing another straight line on the scrap fabric next to the previous line.

Edit

Step 11

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Check the front and back thread tension of the scrap fabric for loose stitches.
The thread tension is correct if there are no loose stitches.
Repeat steps 5-8 as needed to achieve a consistent thread tension without loops on top or bottom of scrap fabric.