Janome Overlocker 644D Instruction Manual

The Janome Overlocker 644D is a professional-grade 3/4 thread overlock sewing machine featuring differential feed, built-in rolled hem, easy threading system, adjustable stitch length and width, free arm capability, built-in thread cutter, and bright LED lighting. Designed for home and professional use, this overlocker handles a variety of fabrics from lightweight to heavy materials. Below are key sections for safety, features, setup, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Installation & Setup 3. First-Time Operation 4. Specifications 5. Controls and Settings 6. Threading Instructions 7. Stitch Selection & Techniques 8. Maintenance & Cleaning 9. Safety Information 10. Troubleshooting

Features at a Glance

Key components: 3/4 thread capability, Differential feed system, Built-in rolled hem, Color-coded threading, Free arm, Built-in thread cutter, LED work light.

FeatureDescription
Differential FeedPrevents stretching or puckering on various fabrics
Built-in Rolled HemEasy conversion for fine edge finishing
Color-coded ThreadingSimplified threading with visual guides
Free Arm CapabilityAccessible for sewing cuffs and sleeves
Built-in Thread CutterConvenient cutting at front of machine
LED Work LightBright illumination of sewing area
Stitch Length ControlAdjustable from 1-4mm
Stitch Width ControlAdjustable from 3.5-7mm
Presser Foot PressureAdjustable for different fabric types
Tension DialsIndividual controls for upper/lower loopers and needles

Installation & Setup

Unpack and inspect all components. Place on stable, level surface.

  1. Remove packaging materials and protective covers from machine.
  2. Attach extension table if included for flatbed sewing.
  3. Install foot controller and connect to power source.
  4. Oil machine according to lubrication points diagram in manual.
  5. Install needles following proper orientation and insertion depth.

WARNING! Machine is heavy; use proper lifting technique. Ensure stable surface to prevent tipping.

First-Time Operation

Power on machine; test basic functions before sewing.

  1. Thread machine following color-coded guides for upper/lower loopers and needles.
  2. Set stitch length and width to medium settings for initial testing.
  3. Test on scrap fabric to check tension and stitch formation.
  4. Adjust differential feed based on fabric type being used.
  5. Practice basic overlocking on various fabric types.

CAUTION! Keep fingers away from moving needles. Always use proper foot control.

Specifications

Controls and Settings

Main controls located on front and side panels. Tension dials for upper looper, lower looper, and needles.

Front Panel: Stitch length dial, Stitch width dial, Differential feed control, Presser foot lever, Power switch.

Thread Tension: Four individual dials (upper looper, lower looper, right needle, left needle). Stitch Length: 1-4mm adjustment for stitch density. Stitch Width: 3.5-7mm adjustment for seam allowance. Differential Feed: Adjustable from 0.7-2.0 for fabric handling. Presser Foot: Quick release lever for changing feet.

Threading Instructions

Follow color-coded threading path for proper operation.

  1. Raise presser foot and needles to highest position.
  2. Follow numbered threading sequence: Upper looper (blue), Lower looper (green), Needles (red/yellow).
  3. Ensure threads are properly seated in tension discs.
  4. Pull threads under presser foot toward back of machine.
  5. Test thread tension on scrap fabric before sewing project.

Tip: Always thread with presser foot raised to ensure proper tension disc engagement.

Stitch Selection & Techniques

Versatile stitch options for various sewing applications.

  1. 3-Thread Overlock: Basic overedging for seam finishing.
  2. 4-Thread Safety Stitch: Strong seam construction with overedge finish.
  3. Rolled Hem: Convert for fine edge finishing on lightweight fabrics.
  4. Flatlocking: Decorative seam technique for stretch fabrics.
  5. Differential Feed Settings: Use lower setting for stretch fabrics, higher for lightweight fabrics.
  6. Gathering: Set differential feed above 1.5 for automatic gathering.
  7. Lettuce Edge: Use on knit fabrics with woolly nylon thread.

WARNING! Always test stitches on fabric scraps. Adjust tension and feed for different materials.

Maintenance & Cleaning

Regular maintenance ensures optimal performance and longevity.

  1. Clean lint and dust from loopers and feed dogs after each use.
  2. Oil machine monthly or after every 10 hours of use.
  3. Use only Janome recommended oil and accessories.
  4. Check needle condition regularly; replace if bent or dull.
  5. Store covered when not in use to prevent dust accumulation.

CAUTION! Unplug machine before cleaning or maintenance. Use only recommended lubricants.

Safety Information

Always follow safety guidelines to prevent injury and machine damage.

Troubleshooting

SymptomPossible CauseCorrective Action
Thread breakingIncorrect threading/tensionRe-thread following color codes; adjust tension settings.
Fabric not feedingPresser foot pressure/feed dogsAdjust presser foot pressure; clean feed dogs; check differential feed.
Uneven stitchesTension/differential feedBalance thread tensions; adjust differential feed for fabric type.
Machine jamsThread buildup/lintClean loopers and feed dogs; remove thread tangles.
Poor rolled hemIncorrect conversion/threadingEnsure proper rolled hem conversion; use appropriate thread.
Needle breakingWrong needle/bent needleUse correct needle system; replace bent needles; check needle insertion.
Looper thread skippingTiming/tension issuesCheck looper timing; adjust looper tensions; re-thread properly.

Service: Contact authorized Janome service center for technical issues. Visit www.janome.com or call 1-800-631-0183 for support.

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