Anvil 090: Mainspring Fabrication, 1812 Springfield

Published on November 13, 2020
Duration: 34:44

This video details the expert-level process of fabricating a replacement mainspring for an 1812 Springfield lock. The instructor, Mark Novak, demonstrates the intricate steps of shaping, welding, heat-treating, and tempering spring steel. Key techniques include forming the spring's geometry for optimal leverage, carefully controlling heat during bending and welding, and achieving the correct hardness and flexibility through precise quenching and tempering in a lead pot. The process emphasizes understanding the functional requirements of the spring within the lock mechanism.

Quick Summary

Fabricating a replacement mainspring for an 1812 Springfield involves shaping steel, welding, hardening through quenching, and drawing back the temper. Drawing temper, often indicated by a blue color achieved by heating in a lead pot, is critical for flexibility and preventing brittleness, allowing the spring to flex without shattering.

Chapters

  1. 00:05Introduction: Broken Spring
  2. 00:54Original Spring Analysis
  3. 01:17Spring Function and Geometry
  4. 03:15Alternative Spring Designs
  5. 04:08Repairing the Broken Spring
  6. 05:16Forming the Upper Limb Tab
  7. 07:00Creating Test Coupons
  8. 07:54Traditional Spring Bending
  9. 10:03Shaping the Spring for Lock Clearance
  10. 11:40Creating the Locating Pin Tab
  11. 13:44Fabricating the Lower Limb
  12. 15:30Reheating and Bending
  13. 16:50Trimming to Length
  14. 18:30Combining Spring Halves
  15. 20:28Welding the Spring
  16. 21:39Quenching the Spring
  17. 23:55Tempering Process: Lead Pot
  18. 25:27Lead Pot Setup
  19. 26:33Safety Tip: Hot Lead
  20. 27:25Tempering Color Indicators
  21. 30:10Tempering Completion
  22. 30:31Cooling After Tempering
  23. 31:08Spring Flexibility Test
  24. 32:02Final Spring Assembly and Tensioning
  25. 32:40Mounting Spring in Lock
  26. 33:42Testing the Lock Mechanism
  27. 34:14Conclusion: Completed Spring

Frequently Asked Questions

How is a replacement mainspring fabricated for an antique firearm like the 1812 Springfield?

Fabrication involves cutting steel to size, bending it to the correct shape, welding the pieces, and then heat-treating. This includes hardening by quenching and drawing back the temper by heating in a lead pot to achieve the necessary flexibility and strength for reliable function.

What are the key steps in heat-treating a newly fabricated firearm spring?

The process involves heating the spring to a high temperature, quenching it in water or oil to harden it, and then drawing back the temper. Drawing temper is done by reheating the spring to a lower temperature, often indicated by a specific color like blue, to reduce brittleness and allow it to flex without breaking.

Why is drawing the temper important for a firearm mainspring?

Drawing the temper is crucial because it balances hardness with flexibility. A spring that is too hard will be brittle and shatter under stress. Drawing back the temper makes the spring resilient, allowing it to bend significantly and return to its original shape repeatedly without fatigue or failure.

What are common sources for spring steel for DIY firearm repairs?

Suitable spring steel can often be salvaged from old metal items like lawnmower blades, edger blades, or circular saw blades. Alternatively, specialized spring steel stock can be purchased from firearm parts suppliers.

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