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Kydex and Nylon Sheaths

How to Make a Knife Sheath with Kydex

Kydex is a category of thermoplastic acrylic polyvinyl-chloride materials with a wide variety of applications. It’s scratch-resistant, waterproof, and holds its shape very well, making it a popular choice for knife sheaths. When using Kydex to make your own knife sheath, follow the instructions below:

 

  1. Make a pattern for your sheath and test it to make sure it will fit properly. You can make a one- or two-piece sheath. You’ll need to leave a ¼” to ⅜” seam allowance for the glued or riveted edge.
  2. Using your pattern, cut the Kydex using a scroll saw or jewelers saw.
  3. Kydex becomes pliable at 300 degrees Fahrenheit. Heating with a heat gun or 1500-watt hair dryer will work nicely. When hot, mold to shape wearing heat-resistant gloves. Work quickly as the material cools rapidly. If you are not satisfied, reheat and try again.
  4. Glue the seams with any good contact cement according to the manufacturer’s instructions. If desired, drill holes and insert any type of leather rivets to further hold the seams.
  5. Sand and smooth the cut edges as desired.

 

Technical Information: Cementing Kydex to Kydex

Due to its excellent chemical resistance, Kydex can be more difficult to cement than other plastics. Strong bonds may be obtained for most applications using the following methods:

 

  1. The best joints can be obtained using a viscous solvent cement consisting of about 10% Kydex shavings or sawdust dissolved in a 50-50 mixture of tetrahydrofuran (THF) and methyl ethyl ketone (MEK). The Kydex shavings should be dissolved in the straight THF first before adding the appropriate amount of MEK. Both of these solvents are available from lab supply companies such as Fisher Scientific, Aldrich Chemicals, or other chemical distributors.
  2. Without the Kydex shavings, you can make a relatively fast-acting capillary adhesive using only the 50-50 THF and MEK mixture. THF works well at 100% but it tends to flash off too quickly, resulting in a poor joint. The addition of MEK slows down the evaporation rate and affords more time to work with the joint.
A premixed, thickened THF gel cement can be obtained from IPS Weld-On. Their phone number is 1-800-421-2677.