How to Make a Butterfly Knife Out of a Multi Tool

Written by david claerr
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How to Make a Butterfly Knife Out of a Multi Tool
Butterfly knife (David A. Claerr)

A standard multitool is a well-crafted and durable device that under normal circumstances can withstand many years of usage. But if used under extreme conditions, the individual tools can break or become dulled, chipped or otherwise unsuitable for the task. This project uses a multitool which has a broken pliers unit. The pivot ends of the pliers are repurposed to serve as a mount for a single, long blade, effectively turning the multitool into a butterfly knife.

Skill level:
Moderately Challenging

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Things you need

  • Metal saws such as hacksaw or metal-cutting band saw
  • Grinders
  • Metal files
  • Welding unit or JB Weld epoxy
  • Needle-nosed pliers
  • Loctite liquid fastener
  • Blade (finished) for knife: premade or custom.
  • Vices and/or clamps

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  1. 1

    Cut and grind off the plier pincers to just above the main pivot point for the pincers. (The pincer pivot point will immobilised by the process of welding or by application of epoxy.) If necessary, the smaller pivots on which the individual blades and tools fold into the handle can be removed by unscrewing with needle-nosed pliers. It takes considerable torque applied to the pivots to loosen them as they are fixed in place with a dried liquid fastener. For a longer blade, removal of a few of the tools opposite the pliers unit is recommended to provide more space.

    How to Make a Butterfly Knife Out of a Multi Tool
    Modifying parts
  2. 2

    Clamp and align the mutlitool and the blade in place. Use metal vices and clamps that resist high temperatures if welding. (I use portable vices that can be clamped to a metal workbench.) The blade must be precisely aligned and centred before either welding or by application of the epoxy to attach the remainder of the pincer unit to the blade. Ensure that the blade is the proper length to fold into the handle prior to attachment.

  3. 3

    Attach the blade to the pincers unit (by weld or epoxy). Allow the weld to cool or the epoxy to set, and then grind and file off the excess metal or epoxy to a smooth, bevelled transition from the pincer unit to the shaft of the blade. Check the folding action of the blade into the handle pieces. It may be necessary to remove a portion of the metal on the handle's pieces at the place where they contact the pliers mounting for the handles to open all the way and meet back-to-back when the blade is in full extension.

  4. 4

    Replace any pivot points that were removed by first applying the Loctite or an equivalent liquid fastener to the threads of the screws before reassembling them. Use care to apply a small amount that will not overflow the joint and interfere with the working of the pivot points. Inspect the joints carefully and wipe away any overflow.

Tips and warnings

  • The welding of the blade should only be attempted by persons with training and experience. Attachment using JB Weld or an equivalent epoxy should be done by an adult or with adult supervision. Use appropriate caution and follow safety procedures at all times. Wear protective gear and safety glasses at all times when working with metalworking tools. Check your local and state ordinances for any possible legal restrictions on carrying the knife in public places.

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