Introduction: Belt Buckle Knife

Is it a simple belt that holds my pants?

Tired of losing knives, I was thinking about making one that was part of my belt, so I made one of 420 stainless steel. This discreetly hides in the belt taking advantage of the shape of the buckle.

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I would also apologize for my English as a non-native English speaker some terms are very difficult for me. Forward, Instructable!! I will be happy to answer any question.

Step 1: Materials and Tools


Stainless Steel sheet 420:

  • This steel is recommended for beginners with stainless steel due to the medium-low level of difficulty to work it.
  • Tempering (oil): 980 to 1030 ºC
  • Hardening: it's recommended a temperatura range from 100 to 190 ºC (minimum recommended time is of 50')

Old belt

One metal nail

Kidex (black)

A selection of sandpaper from coarse grit to as fine as you can get

Super glue


Hand tools

Metal files




Drill bits


Mitutoyo caliper

Sharpening stone

Power Tools

BTS900 Scheppach Belt sander

Optimum B14 Drill press

Goxawee 240W Die grinder

Bosch Grinding machine

Proxxon fd150 Mini lathe


Heat Gun

Step 2: Drawing and Cut

Using a stainless steel sheet 420 (5x40x150mm) I began marking the silhouette (document attached). To make this easier and not to move the papel I used small neodymiums which were very useful :-))

Once the silhouette marked using the grinding machine roughly cut out the knife outline leaving about 2mm of waste around the profile.

Step 3: Defining Silhouette

I used the belt sander to gradually work down the profile until I reach the line I made all the way around.

For hard-to-access curved areas I used round metal files and finally with a die grinder for a finer finish.

The 420 steel untempered works fairly easily with power and hand tools (metal files), but once hardened it does not allow manual machining.

Step 4: Buckle

To empty the interior of what the buckle will be, previosuly I delimited the area and drilled the entire contour with the idea of removing as much material as possible. In this way, later it would be easier for me to finish cutting it with the disk of the die grinder.

Finally, I filed all the areas leaving the interior with a uniform appearance.

Step 5: Bottle Opener

At first, I did not have the idea of adding an opener to the knife, but I thought that if I did not make it, someday I would regret it :-))

So I returned to the initial drawing and marked the area where the opener would be. I drilled a hole with a drill bit and cut the rest with the metal saw.

Step 6: Adding the Bevel

Draw a line down the middle of the steel where you want the edge of the blade to be.

Clamp the blade horizontally to a table and use the file to slowly grind the edge to add the chamfer profile.

I decided to make it this way to have more control and that the angle was always the right one. It worked great but takes a while! :-(

Turn the blade over and repeat on the other side.

Using sand paper to gradually sand out all of the marks created by the file and create a good finish. Firstly I used rough grains until finish using 1000 grit paper. It is important to make sure that the whole blade is sanded!

Finally, I wanted to give it a sharpening in the water stones before give the blade is heat treated.

Step 7: Prong Belt

I take advantage that the metal is not yet tempered to make two holes that I will use later to put the prong of the buckle and a piece that will prevent the knife from coming loose from the belt.

Step 8: Heat Treating

The treating actually quite hard to complete accurately, heating the steel to a temperature 980º-1030º (Stainless 420) and then quenching in oil of the car, this hardens the blade and makes it very brittle.

The next stage to the process is tempering, I heated the oven of my house to 200º and I introduced the knife during approximately one hour.

This process requires a lot of practice and knowledge. Sure that in this operation I made mistakes but I think that is where you learn (learn by trial and error).

Finally after all the process, the metal acquires a dark tone that I removed it using sandpaper with soapy water.

Step 9: Prong Belt

To make the prong of the buckle I use one metal nail, which I process in the belt sander turning it into a 50mm long stainless bar. I file one of its sides leaving a smooth surface and with a hammer and patience I give it the desired shape .

Step 10: Knife Stopper

For fixing the knife to the belt, I made a small stainless steel piece with my little lathe, which I later heated red-hot and hammered until it was fixed in the knife.

This type of pieces are sold with different fastening systems but I decided to make it myself to practice with my small Proxxon lathe :-)

Step 11: Sheath Part Under the Belt

For the sheath I used Kydex which is a thermoplastic sheet which can be molded to form-fit nearly any shape.

Using an old belt which had nothing special, I cut its buckle and I made a hole in which would fit the piece that I made with the lathe.

Then, with a piece of black kydex I put it over the knife and heat it with a heat gun. I put foam quickly and press it with clamps. After a couple of minutes, when removing the clamps the kydex will have hardened and will have the shape of the knife!

I cut the piece of kydex to the size of the belt and glue it with super glue. After a few days using the belt, I decided also to sew the piece of kydex giving it more resistance.

Step 12: Final Conclusions

I am very happy with the final result and everything went more or less as expected.

Based on this idea, different designs can be made according to the needs of each one, such as a multi-tool.

I hope you liked it and that someone gives the desire to make one.

See you soon!