Desheng Rotary Hook Instruction Manual

1. Introduction

This manual provides essential information for the installation, operation, and maintenance of the Desheng Rotary Hook, designed for industrial double needle sewing machines. This component is crucial for the proper functioning of your sewing machine, ensuring consistent stitch formation and reliable performance. Please read these instructions carefully before attempting any installation or maintenance.

2. Product Overview

The rotary hook is a precision-engineered component responsible for catching the needle thread loop and forming a lockstitch. This specific rotary hook is manufactured to meet the specifications required for high-performance industrial sewing applications.

Figure 1: Front view of the Desheng Rotary Hook. This image displays the main body of the rotary hook, including the bobbin case area and the shaft, highlighting its metallic construction and precise design.

Figure 2: Two views of the Desheng Rotary Hook. One hook is shown fully assembled, while another is positioned to show its internal structure or a different angle, emphasizing its robust build.

3. Compatibility

This Desheng Rotary Hook is compatible with the following industrial double needle sewing machine models and part numbers:

• Juki Models: LH-3168
• Sunstar Models: KM-790
• Equivalent Part Numbers: 226-88253, DSH-3168, H12-15LC

Always verify the part number and machine model before installation to ensure correct fitment.

4. Installation

Replacing a rotary hook requires precision and familiarity with industrial sewing machine mechanics. It is highly recommended that installation be performed by a qualified sewing machine technician. Incorrect installation can lead to machine damage or poor stitching performance.

General Installation Steps (Consult your machine's service manual for detailed instructions):

1. Safety First: Disconnect the sewing machine from its power source before beginning any work.
2. Access the Hook Area: Open the necessary covers and remove any components obstructing access to the rotary hook. This may include the needle plate, feed dogs, and bobbin case.
3. Remove Old Hook: Carefully unfasten the screws or retaining clips holding the old rotary hook in place. Note the orientation and position of all parts.
4. Clean Area: Thoroughly clean any lint, dust, or old lubricant from the hook race and surrounding mechanisms.
5. Install New Hook: Position the new Desheng Rotary Hook into the machine, ensuring it aligns correctly with the drive shaft and timing marks (if applicable).
6. Secure Hook: Fasten the new hook using the original screws or retaining clips. Do not overtighten.
7. Timing Adjustment: This is a critical step. The rotary hook timing must be precisely set in relation to the needle bar movement. Refer to your specific machine's service manual for exact timing procedures. Incorrect timing will result in skipped stitches, thread breakage, or machine damage.
8. Reassemble: Reinstall all removed components (bobbin case, feed dogs, needle plate, covers).
9. Test: Reconnect power and perform test stitches on scrap fabric to verify proper function and stitch quality. Adjust tension as needed.

Note: Always refer to the official service manual for your Juki LH-3168 or Sunstar KM-790 machine for precise, model-specific installation and timing instructions.

5. Operation (Function within Machine)

Once correctly installed and timed, the Desheng Rotary Hook operates as an integral part of the sewing machine's stitch formation mechanism. As the needle descends and then rises, it forms a loop of upper thread. The rotary hook's point catches this loop, carries it around the bobbin case, and interlocks it with the bobbin thread, creating a secure lockstitch. Proper functioning of the rotary hook is essential for smooth sewing, consistent stitch quality, and preventing thread jams or breakage.

6. Maintenance

Regular maintenance of the rotary hook and its surrounding area is vital for extending the life of the part and ensuring optimal machine performance.

• Cleaning: Regularly remove the bobbin case and clean out any lint, dust, or thread fragments from the hook race and bobbin area using a brush or compressed air. Accumulation can impede hook movement and affect stitch quality.
• Lubrication: Apply a small amount of high-quality sewing machine oil to the hook race and other specified lubrication points as indicated in your machine's service manual. Frequency of lubrication depends on machine usage; typically, daily for industrial machines.
• Inspection: Periodically inspect the hook point for any burrs, nicks, or wear. A damaged hook point can cause thread breakage or skipped stitches. If damage is observed, the hook should be replaced.
• Bobbin Case: Ensure the bobbin case is clean and free from damage. A worn or damaged bobbin case can also affect stitch quality.

7. Troubleshooting

If you experience issues after installing or during the use of the rotary hook, consider the following common problems and solutions:

• Skipped Stitches:
  • Check needle installation (correct size, type, and insertion).
  • Verify hook timing. This is the most common cause of skipped stitches related to the hook.
  • Inspect the hook point for damage.
  • Ensure proper thread path and tension.
• Thread Breakage (Upper or Lower):
  • Check for burrs or sharp edges on the hook, needle plate, or bobbin case.
  • Ensure correct thread tension.
  • Verify hook timing.
  • Clean lint from the hook area.
• Noisy Operation:
  • Insufficient lubrication.
  • Loose components in the hook area.
  • Incorrect hook timing causing parts to rub.
• Poor Stitch Quality (Loose, Uneven Stitches):
  • Incorrect thread tension (upper and lower).
  • Lint accumulation in the bobbin case or hook race.
  • Worn bobbin case or hook.

If problems persist, consult a professional sewing machine technician or refer to your machine's comprehensive service manual.

8. Specifications

9. Warranty and Support

For specific warranty information regarding your Desheng Rotary Hook, please refer to the documentation provided at the time of purchase or contact your retailer. As this is a replacement part, its warranty may be covered under the terms of the original purchase or by the manufacturer directly.

For technical support or further assistance with installation and troubleshooting, it is recommended to consult the official service manual for your Juki LH-3168 or Sunstar KM-790 sewing machine. You may also contact a certified sewing machine technician for professional service.