Singer 6620C Heavy Duty Sewing Machine Manual

The Singer 6620C is a heavy-duty sewing machine designed for tackling thick fabrics like denim, canvas, and leather, as well as everyday sewing projects. It features a powerful motor, a variety of built-in stitches, automatic needle threader, adjustable presser foot pressure, top drop-in bobbin, and a durable metal frame. Below are key sections for safety, features, setup, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Heavy-duty metal frame, built-in stitch panel, automatic needle threader, top drop-in bobbin system, adjustable presser foot lever, reverse stitch button, stitch length/width dials.

Unpacking and Setup

Unpack and inspect all contents. Place on a stable, flat surface.

1. Remove machine from box: Lift by the carrying handle, not by the free arm.
2. Attach power cord: Plug the foot controller into the machine, then plug both the machine and controller into a 120V AC outlet.
3. Install needle: Use the included screwdriver to loosen the needle clamp screw, insert needle with flat side to the back, tighten screw.
4. Wind and insert bobbin: Follow threading diagram to wind bobbin, then place in bobbin case.
5. Thread upper thread: Follow numbered path on machine, use automatic needle threader.

WARNING! Machine is heavy; lift with care to avoid back injury. Keep fingers away from needle during operation.

First-Time Operation

Power on machine; practice on scrap fabric first.

1. Select stitch: Turn stitch selection dial to desired pattern (e.g., straight stitch).
2. Adjust settings: Set stitch length to 2.5 and width to 0 for basic straight stitch.
3. Position fabric: Lower presser foot lever; gently guide fabric without pulling.
4. Start sewing: Press foot controller slowly to begin; use reverse lever to lock stitches.
5. Finish: Raise needle to highest position, lift presser foot, remove fabric, and trim threads.

CAUTION! Always turn handwheel toward you (counter-clockwise) to avoid timing issues. Unplug machine when not in use or during maintenance.

Specifications

• Model: Singer 6620C Heavy Duty
• Stitches: 23 Built-in stitches (6 basic, 7 stretch, 10 decorative)
• Stitch Length: Adjustable up to 6mm
• Stitch Width: Adjustable up to 6mm
• Speed: Up to 1,100 stitches per minute
• Bobbin: Class 15 transparent top drop-in
• Needle: HAx1 sewing system, size 14/90 recommended for heavy fabrics
• Presser Feet: Snap-on, includes all-purpose, zipper, buttonhole feet
• Power Source: 120V AC, 60Hz
• Warranty: 25-year limited warranty

Controls and Settings

Main controls located on front and side of machine.

Front Panel: Stitch selection dial, stitch length dial, stitch width dial, reverse stitch lever, presser foot lifter.

Side/Under Area: Bobbin winder spindle, handwheel, tension dial (default 4-5), presser foot pressure dial (adjust for fabric thickness).

Basic Settings: For straight stitch: Length 2.5, Width 0, Tension 4-5. For zigzag: Length 2, Width 3-4. For buttonhole: Use automatic buttonhole foot and follow markings.

Stitch Selection and Applications

Select stitch based on fabric and project type.

1. Straight Stitch (Pattern 1): General sewing, seams. Use length 2.5-3 for medium weight fabrics.
2. Zigzag Stitch (Pattern 2-4): Finishing edges, sewing stretch fabrics, appliqué.
3. Stretch Stitches (Patterns 5-11): For knits and elastic fabrics to prevent popped seams.
4. Decorative Stitches (Patterns 12-23): For embellishment on home decor and garments.
5. Buttonhole Stitch (Pattern 0): One-step automatic buttonhole with buttonhole foot attached.

Tip: Always test stitch settings on a scrap of your project fabric first.

Threading and Bobbin Winding

Correct threading is essential for proper stitch formation.

1. Upper Threading: Follow numbered path: from spool pin, through thread guides, down to tension discs, up and through take-up lever, down to needle. Use automatic needle threader for final step.
2. Bobbin Winding: Place spool on pin, thread through bobbin winder tension disc, wrap thread around bobbin 3-4 times, push bobbin winder to engage, press foot controller. Stop when full.
3. Inserting Bobbin: Place wound bobbin in case with thread running counter-clockwise; pull thread through slot and under tension spring. Drop case into machine until click.
4. Drawing Up Bobbin Thread: Hold upper thread tail, turn handwheel toward you until needle goes down and up; pull upper thread to bring bobbin thread up through needle plate.

WARNING! Ensure presser foot is raised when threading upper thread to allow thread to seat properly in tension discs.

Maintenance & Cleaning

Unplug machine before any maintenance. Regular cleaning prevents lint buildup.

1. Daily: Remove needle plate screws; use small brush to clean lint from feed dogs and bobbin area.
2. Monthly: Add a drop of sewing machine oil to hook race and other moving parts as indicated in manual (avoid oiling motor).
3. Needle: Replace needle after every 8 hours of sewing or with each new project.
4. Exterior: Wipe with soft, dry cloth. Do not use solvents or sprays.

CAUTION! Never blow into machine as moisture can cause rust. Use only Singer recommended oil.

Regulatory Information

FCC Part 15: Class B digital device; complies with interference limits for residential use. Copyright © Singer Manufacturing Company. Trademarks of Singer. For support, visit www.singer.com or contact 1-800-4-SINGER. This product is designed for household use.

Troubleshooting

Reset: Unplug machine for 60 seconds to reset electronic components if issues persist.

Service: 1-800-4-SINGER; www.singer.com for authorized service centers.