How to Make a Kydex Knife Sheath

A knife sheath not only protects you from being injured (that’s obvious), but also keeps the knife protected! A well made sheath will ensure the cutting edge stays sharp, the blade will not get damaged when carried, stowed in a pack, or when stored with other knives and tools. Traditional leather sheaths are great, but newer advanced plastics like Kydex make great looking, lightweight, extremely rugged alternative sheaths that are nearly indestructible. Plus, Kydex won’t rot or mildew if it gets wet, and won’t hold water like leather – which can cause carbon steel knives to rust or corrode. Kydex is very easy to work with, whether using normal hand tools, or more advanced shop tools. Since it is easy to thermoform, the sheath can be custom made to the exact contours for the individual knife for maximum protection.

Difficulty: Moderate

Instructions

Things You'll Need:

• Supplies:
• Kydex sheet (.060 to .090” thick for larger blades)
• Sheath press for forming Kydex
• Blue painters tape
• White chalk, grease pencil or marker
• Hacksaw, jigsaw or band saw
• File, scotchbrite pad
• Eyelets or rivets
• Heat source (oven, heatgun)
• MSHA/NIOSH approved respirator or dust mask
• Protective eyewear
• Oven mitts or heavy workgloves
• Optional: belt clip, such as a Teklock
• Note: A used toaster oven makes a good, cheap heat source. A high temp heat gun can also be used, but it is more difficult to heat the plastic consistently.

1. Protect the knife by covering the blade with wide blue painter’s tape. You might want to wrap the handle as well while you’re at it.

2. Cut a sheet of Kydex to 2 – 3” longer than the knife blade, and 4 – 5 times wider than the knife blade. Allow plenty of excess. Typically, Kydex will have a smooth side (inside of finished sheath) and a pebbled or textured side (outside of the finished sheath).

3. Lay the Kydex smooth side down on an aluminum foil covered cookie sheet, and place in toaster oven. Heat the Kydex at 275 - 300 deg F. for 7 – 10 minutes. Check it often! The Kydex should be “floppy” soft when it’s ready to use.

4. CAUTION! Use heavy mitts or workgloves to remove the hot Kydex from the oven.

5. Fold the Kydex in half over the knife (smooth side against the blade), working the fold tight against the spine. Make sure it overlaps up onto the knife handle by at least 1”.

6. Quickly place the wrapped blade in the press between the pads, cover and clamp tightly. Allow the assembly to cool completely before removing from the press.

7. Draw the finished outline on the sheath with chalk, staying about 1/2” away from the original knife profile. Try to keep the cut shape simple, smooth and uncomplicated.

8. Remove the knife by carefully prying open the sheet. Remove the painter’s tape from the knife.

9. Cut out the shape, staying just on the outside of the line. Use a course toothed hacksaw blade, or a very low speed jigsaw or bandsaw. The plastic will melt very easily, so use a low blade speed and high feed rate of material into the saw.

10. Trim the handle area of the sheath. Trim a little at a time, test fitting the knife as you go until you are comfortable with the shape you’ve chosen. Use rounded corners here, since this is where your hand will be touching the sheath when grabbing the knife during use, and you don’t want any sharp edges or corners.

11. Clean-up the cut edge using a medium file, or a scotchbrite pad. If you’re careful, you can use a belt or disc sander. Be sure to wear proper eye protection and respirator. Use compressed air to clean off all debris, especially inside the sheath!

12. If using a belt clip, determine where and how you want to mount it – vertical carry, horizontal carry, or a hybrid. Mark eyelet locations along the edge that will match the belt clip mounting hole spacing (typically 1-1/2” or 2”), all the way towards the tip to keep the sheath tight. Also recommend drilling a “drain hole” where the very tip of the knife will be, to aid in cleaning out the sheath.

13. Drill holes the appropriate size for the eyelets, rivets or mounting screws you intend to use.

14. Install eyelets or rivets using the proper setting tools for the hardware you’ve chosen.

15. You’ll want the knife to “click” into the sheath – this will keep the knife secure when carried on the waist. To do this, flare or tighten the handle opening of the sheath as needed by spot heating small areas with a heat gun, lighter or candle flame to soften it. Take care not to melt or scorch the plastic! Mold the plastic using your fingers until the desired shape is achieved. Wear gloves!
    Tip: Heat an area, form it with your fingers, then quench it under cold running water to quickly set the form.

16. Attach the belt-clip using machine screws or rivets.

Tips & Warnings

• An alternative to the wrap method above is to use two pieces of Kydex to sandwich the blade. Simply start with two pieces instead of one, following the instructions skipping Step 6.
• You can buy a commercial press, or see my How to Make a Kydex Press if you want to save some money!
• If you don't like your first attempt, try reheating and reforming until you achieve the desired results.
• CAUTION! Handle hot Kydex with oven mitts or heavy work gloves to avoid serious skin burns!
• Always wear proper safety equipment (including safety glasses and a respirator) when working with hand or power tools.
• Avoid breathing Kydex dust by using an approved respirator.