Introduction
The Singer 31-15 is a legendary industrial straight-stitch sewing machine widely known as the "Tailor's Machine." From 1900 to 1958, this workhorse powered countless tailor shops, garment factories, and military production facilities around the world. As a core member of the Singer Class 31 industrial family, the 31-15 represents the pinnacle of mechanical sewing machine engineering—built to last over 100 years with proper care.
Production & Manufacturing History (1900-1958)
The Singer Model 31-15 was primarily manufactured in Elizabethport, New Jersey, which was Singer's flagship factory in the United States. However, because Singer operated a massive global manufacturing network, variations of the Class 31 were also produced internationally at other major facilities:
Global Manufacturing Locations
- Kilbowie, Clydebank (Scotland): Machines made here are designated with a "K" suffix, such as the 31K15.
- Wittenberge (Prussia/Germany): Designated with a "D" suffix.
- Monza (Italy): Designated with an "M" suffix.
- St. John's (Quebec, Canada): Designated with a "J" suffix.
Locating and Decoding Your Serial Number
The serial number on a Singer 31-15 is crucial for determining its exact date and place of manufacture, and can be easily deciphered using online databases.
Finding the Serial Number
Location: On most vintage industrial Singer machines like the 31-15, the serial number is a long number stamped directly into the bed (flat top surface) of the machine, often near the pillar or the model number plate.
Serial Number Format
The serial numbers generally fall into two main categories based on their era:
- Pre-1900s: These serial numbers consist of only digits (up to 8 numbers).
- Post-1900s: These are more common for the 31-15 and start with one or two letters followed by six digits (e.g., G1234567 or AB123456).
Decoding the Serial Number
The letter prefixes indicate the specific factory location and the production batch allotment date. For example, a "G" prefix often refers to the Elizabethport, New Jersey factory, and the subsequent numbers can be cross-referenced with production tables to find the exact date the batch was made. The "K" prefix signifies production at the Kilbowie, Scotland, factory.
Using the Serial Number for Information
ISMACS Database: The most widely recommended resource for dating a Singer machine is the International Sewing Machine Collectors' Society (ISMACS) website's serial number database. By entering the specific serial number, you can find the precise date of manufacture and the factory location.
Important Note: Don't confuse the patent dates listed on separate plates (which can be as early as the 1890s) with the actual manufacturing date of your specific machine, which is determined only by the unique serial number.
The Complete Class 31 Family
The Class 31 was one of Singer's most extensive industrial classes, with dozens of specialized sub-models designed for specific manufacturing tasks. While the 31-15 is the most famous for general tailoring, other notable variations include:
Notable Class 31 Models
- 31-15: The standard drop-feed straight stitch for cloth and light leather—the most common and versatile model.
- 31-19: A specialized model for binding and edge work.
- 31-20: Known for having a larger bobbin and shuttle for high-thread-capacity work.
- 31-32: Distinguished by having a reverse function, which the 31-15 lacks.
- 31-44 & 31-45: Specifically modified for shoe manufacturing, such as stitching tongues and boot uppers.
- 31-53 to 31-60: Specialized two-needle machines for parallel stitching on fabrics and shoes.
- 31K47: A rare variation featuring a built-in walking foot mechanism for heavy materials.
In total, historical parts lists and registries indicate there were over 40 distinct sub-models within Class 31, each tailored for specific industrial applications ranging from lace darning to heavy boot stitching.
Technical Specifications
Understanding the technical specifications of the Singer 31-15 is essential for proper operation and parts sourcing:
Needles
The 31-15 uses the common DBx1 industrial needle system (also known as 16x257, 16x231, or 1738). We carry both standard point needles for general fabrics and leather point needles for heavy materials.
Presser Feet
The machine is compatible with various industrial presser feet, including specialized roller feet for leather and heavy materials. For heavy-duty applications, a walking foot attachment can be added to help feed thick materials evenly. The availability of numerous feed dogs and needle plates allows customization for different fabric types and applications.
Bobbins & Bobbin Case
The 31-15 uses Class 15 bobbins (Style A), similar to those found in many vintage home machines. However, it requires a specific 31-15 bobbin case (part #62740). We stock metal bobbins #2996 designed specifically for Singer industrial models.
Power Source & Belting
Originally sold as a treadle-powered machine for small shops, most 31-15 machines were later fitted with electric clutch motors or modern servo motors in industrial tables. These machines typically use 5/16" leather belting for the motor belt connection.
Construction
The Singer 31-15 is an all-metal machine built with cast iron and heavy steel components. This robust construction is why these machines can easily last over 100 years if properly maintained.
Historical Significance
The "Tailor's Standard"
The 31-15 was the staple machine in nearly every tailor shop in the early 20th century due to its precision and reliability. Its ability to produce consistent, high-quality straight stitches made it indispensable for professional garment makers.
World War II Contribution
During World War II, the Singer 31-15 was extensively used by the military and in factories to produce uniforms, tents, and army bags. Its durability and speed made it essential to the war effort.
Design Innovations
The 31-15 featured a knee-lift mechanism for hands-free presser foot operation and an oscillating shuttle that allowed for smooth operation at high speeds—innovations that were ahead of their time.
Singer's Marketing & Selling Points
Singer marketed the 31-15 with several key advantages:
Robustness & Simplicity
Marketed to small shops without on-site mechanics because it was extremely durable and only required simple oiling for maintenance.
Versatility
Capable of handling a vast range of fabrics, from lightweight wovens to heavy canvas, denim, and even light garment leather.
High-Speed Efficiency
Designed to sew quickly and reliably, making it ideal for the high-volume demands of professional garment manufacturing.
Common Uses Today (2026)
The Singer 31-15 remains a respected tool in 2026, prized for its mechanical simplicity and historical longevity:
Small Artisan Shops
Frequently used for tailoring, alterations, and garment repairs by craftspeople who appreciate vintage machinery.
Medium-Weight Materials
Capable of handling broadcloth, heavy canvas, denim, coating, and blankets with ease.
Light Leather Work
Suitable for soft clothing leather, pigskin wallet interiors, and small leather goods. Note: not intended for heavy saddle work or thick upholstery leather.
Quilting & Topstitching
Favored for straight topstitching and machine quilting due to its precise stitch quality and consistent tension.
Maintenance Tips
Keeping your Singer 31-15 running smoothly requires regular attention:
Frequent Oiling
Requires manual lubrication before use. Apply one drop of sewing machine oil to all moving metal parts and designated oil holes.
Lint Removal
Regularly brush out dust from the bobbin area, feed dogs, and under the needle plate after every project to prevent buildup.
Needle Replacement
Replace the DBx1 needle every 8–10 hours of sewing to prevent skipped stitches or fabric damage.
Professional Servicing
Even with home care, an annual inspection by a technician is recommended to ensure timing and tension remain accurate.
Why the Singer 31-15 Is Still Popular
Indestructible Build
Built with cast iron and heavy steel components, these machines can easily last over 100 years if properly maintained—a testament to early 20th-century American manufacturing.
Parts Availability
Because millions were produced, replacement parts like bobbins, bobbin cases, and presser feet are inexpensive and widely available.
Ease of Modification
Users often replace original clutch motors with modern servo motors for silent operation and superior speed control, bringing vintage reliability into the modern era.
Comparison to Modern Industrial Machines
| Feature | Singer 31-15 (Vintage) | Modern Industrial Machines |
|---|---|---|
| Reverse | Generally lacks a reverse function | Standard on almost all modern models |
| Speed | Approx. 2,200 stitches per minute | Can exceed 5,000+ stitches per minute |
| Electronics | None (Fully mechanical) | Often include auto-backtack and thread cutters |
| Lubrication | Manual oiling required | Many feature automatic "dry head" or oil bath systems |
| Versatility | Excellent for various fabric weights | Often specialized for specific fabric types |
Parts & Accessories
At Central Michigan Sewing Supplies, we stock a comprehensive selection of Singer Model 31 parts and accessories, including:
- DBx1 industrial needles (standard and leather point)
- Industrial presser feet and attachments
- Metal bobbins #2996
- Bobbin case #62740
- Genuine Singer walking foot attachments
- Leather motor belts (5/16" diameter)
- Feed dogs and needle plates for various applications
Conclusion
The Singer Model 31-15 truly deserves its reputation as the "Tailor's Machine." Its combination of robust all-metal construction, mechanical simplicity, and versatile capabilities make it as relevant today as it was over a century ago. Whether you're running a small artisan shop, working with medium-weight fabrics and light leather, or simply appreciate the craftsmanship of vintage industrial machinery, the Singer 31-15 represents the best of American manufacturing excellence.
Looking for parts or accessories for your Singer 31-15? Browse our complete selection of Singer Model 31 parts to keep your legendary machine running for another 100 years.