Singer 31 15 Sewing Machine Manual

The Singer 31 15 is a classic industrial sewing machine designed for heavy-duty stitching applications. This straight stitch machine features a high-speed capability, automatic lubrication system, reverse stitching function, and robust construction for continuous operation. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Threading and Bobbin 7. Stitch Adjustment 8. Maintenance Schedule 9. Care & Cleaning 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Heavy-duty frame, automatic lubrication system, reverse stitch lever, tension control, bobbin winder, presser foot, and needle bar.

Feature	Description
Stitch Type	Straight stitch only
Stitch Length	Adjustable 1-6mm
Speed	Up to 4500 stitches per minute
Needle System	DBx1 industrial needles
Lubrication	Automatic oil circulation system
Presser Foot Lift	Manual and knee lift options
Reverse Stitch	Lever-operated reverse stitching
Bobbin Type	Rotating hook with Class 15 bobbins
Motor	Industrial clutch motor
Thread Tension	Upper and lower tension adjustment

Installation

Unpack and inspect contents. Place on industrial table or stand.

Mount machine: Secure to industrial table using mounting screws provided.
Install motor: Attach clutch motor to machine head and connect drive belt.
Connect power: Plug into appropriate industrial power outlet (check voltage requirements).
Oil system: Fill oil reservoir with recommended sewing machine oil.

WARNING! Machine is heavy; use proper lifting equipment. Ensure stable mounting before operation.

First-Time Setup

Power on machine; perform initial setup procedures.

Thread machine: Follow threading diagram for upper and lower threading.
Install needle: Insert DBx1 needle with flat side facing back, tighten screw.
Wind bobbin: Use built-in bobbin winder with thread tension properly set.
Test stitch: Run machine on scrap fabric to check stitch quality and tension.
Adjust settings: Set stitch length and tension according to fabric type.

CAUTION! Keep fingers away from needle area during operation. Always disconnect power when threading or changing needles.

Specifications

Machine Type: Industrial Straight Stitch
Stitch Length: 1-6mm adjustable
Maximum Speed: 4500 SPM
Needle: DBx1 system, sizes 11-21
Presser Foot Lift: 10mm standard, 16mm with knee lift
Bobbin: Class 15, metal recommended
Thread: Tex 40 to Tex 120
Motor: Clutch motor, 550W
Power Requirements: 220V/380V, 50/60Hz
Machine Weight: 35kg

Controls and Settings

Main controls: Handwheel, reverse stitch lever, stitch length regulator, tension dials, presser foot lever.

Handwheel: Manual operation and needle positioning. Reverse Lever: Engage for back-tacking. Stitch Length: Rotate dial for longer/shorter stitches. Upper Tension: Adjust with numbered dial (higher number = tighter tension). Bobbin Tension: Adjust screw on bobbin case.

Presser Foot Pressure: Adjust spring for different fabric thickness. Needle Position: Center needle position standard.

Threading and Bobbin

Proper threading is essential for optimal performance.

Upper Threading: Follow numbered guides from spool to needle.
Bobbin Winding: Place spool on winder, thread through tension, engage clutch.
Bobbin Insertion: Drop bobbin into case, pull thread through slot and under tension spring.
Bring Up Bobbin Thread: Hold upper thread, rotate handwheel to catch bobbin thread.

Tip: Always pull both threads under and behind presser foot before starting.

Stitch Adjustment

Adjust settings for different fabrics and applications.

Stitch Length: 1-2mm for lightweight fabrics, 3-4mm for medium, 5-6mm for heavy materials.
Thread Tension: Balanced when threads lock in middle of fabric layers.
Needle Size: Smaller for fine fabrics, larger for heavy materials.
Presser Foot Pressure: Increase for slippery fabrics, decrease for stretch materials.

WARNING! Always test settings on scrap fabric before sewing your project.

Maintenance Schedule

Regular maintenance ensures long machine life and consistent performance.

Maintenance Task	Frequency
Oil reservoir check	Daily
Needle change	Every 8 hours or when dull
Bobbin area cleaning	Daily
Hook race cleaning	Weekly
Full lubrication	Monthly
Motor maintenance	As per motor manual
Professional service	Annually

Care & Cleaning

Disconnect power before cleaning. Remove lint and dust regularly.

Daily: Brush out lint from bobbin area and feed dogs.
Weekly: Clean hook race and remove accumulated thread ends.
Monthly: Wipe exterior with soft, dry cloth.

CAUTION! Use only recommended sewing machine oil. Do not use compressed air for cleaning.

Regulatory Information

CE certified for industrial use. Complies with international safety standards for industrial machinery. Copyright © Singer Manufacturing Company. For technical support and service, contact authorized Singer service centers. Original equipment manufacturer specifications must be followed for warranty compliance.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Thread breaking	Incorrect tension/needle	Check threading; adjust tension; replace needle
Skip stitches	Wrong needle/bent needle	Replace needle; check needle size for fabric
Uneven stitches	Tension imbalance	Balance upper and lower tension
Machine jams	Thread buildup	Clean hook race; rethread properly
Noisy operation	Low oil/loose parts	Check oil level; tighten mounting screws
Motor not running	Power issue/belt	Check power connection; inspect drive belt

Service: Contact authorized Singer service center for major repairs.

Warranty: 1 year on parts and labor when serviced by authorized centers.