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E167: Basics of Knife and Kydex Making with Bob Hill

In this episode, we sit down with Bob Hill; knife maker, Kydex maker, and owner of Bob Hill Blades. He’s going to share with us the basics of knife making, how to work with Kydex, and a host of other maker topics.

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Knife Making and Kydex Making Topics Discussed:

  • How does someone start learning to make knives?
  • How much tooling up does it take to get into knife making?
  • How do you determine what angle to put on a knife and does the metal play any part in it?
  • How long does it take to become proficient at knife making?
  • Why has Kydex almost replaced leather for holsters and knife sheathes?
  • What tools would they need for Kydex sheath and holster making?
  • How expensive is it for a hobbyist to get started making things in Kydex?
  • Besides holsters and knife sheathes, what else can you make out of Kydex?

Quick Takeaways from this Knife Making and Kydex Making Episode:

What’s the best way for someone to learn knife making?

What I would suggest to a lot of folks… a number of the supply companies… professional companies where they host grind-ins or hammer-ins… there’re clubs that hosts those… a buddy of mine Mike Stewart, he owns Bark River Knives… he hosts three grind-ins a year. And you can go in and see the full process of how they make a knife. And you actually go in and you make a knife. You do as little or as much as you want.

What’s the learning curve on making a knife?

The people I’ve had come here to my shop to learn how to make a knife […] to really achieve what they have in their mind, it can take a few blades. But the actual getting something functional, might not be pretty, but it’ll get the job done, not that bad. I’d say one weekend. […] That includes some of the metallurgy as well.

How much tooling up does it take to make knives?

You can make a knife with just files. […] Action filing. You’re using files to a fairly high tolerance. Like thousands of an inch. […] I filed out a small drop point hunter on a Saturday.

[For the beginner] forging, I’m a big fan of the gas air forge. […] You can build your own for about fifty to sixty dollars. […] You need to have a good anvil and a good base. Then you’re going to buy a ton of hammers. […] You’ll evolve into it. […] But if someone wants to do hobby where they do stock removal, really you could get away with […] you need some kind of belt grinder to be able to remove material and be able to shape the knife… grind the bevels. Basically take away all the material that isn’t the knife. […] You’ll use that on everything whether you’re doing Kydex, or leather sheathes… you’ll use that to sharpen the knife if you have a good variable speed one and the appropriate belts. It’s the tool that you use the most. […] I would be looking at the 2 inch by 72 inch belts; they’re the standard. They’re a bit more expensive, but if you’re really really wanting to throw down into it. […]

Where does forging come in?

Forging is nice if you want to be efficient with the materials. […] It can also be very helpful if you know what you’re doing with the heat treating to actually refine the grain structure. […] They’ll anneal out any of the grain structure that they create into it. […] It ends up being as if it was a homogeneous piece of steel. […] With forging, you can really go fast getting the material shaped…

In layman’s terms, why does the grain structure of a knife matter?

They’re not even going to see it. That’s going to be the polish and the finish. […] I’ll make word carving chisels for people that have to have a degree of spring. The way that I’m doing those, I want the grain structure to be a certain way so they’ll be strong when they’re flexing. […] It’s like that last 5% of performance they’re trying to get out of it.

How important is blade geometry?

The overall geometry is probably the most important aspect of it [knives]. […] The basics of the edges where you have hollow grind or a concave grind […] it’ll have a radius [facing into the blade]. Then you’ll have flat grind and your convex [grind – radius facing out]. The strongest edge, of course, is convex. Next is the flat grind. Then the hollow grind. Depending upon what you’re cutting, if you’ll notice the straight razors and things like that, they’ll be hollow grind. It’s a very feather edge–it’s very light; not very strong. Flat grind kind of in-between can be very very sharp, but a little bit stronger. Then convex, which can also be ridiculously sharp, but stronger still. […] But grinding, setting your edge, and having it be geared towards the task you want to achieve. [For example] all of my camp knives are going to be convex and fairly tall grinds. They’re not going to be a super thin edge, but still convex so that it spreads […] if you’re chopping into something it spreads. It’s not going to be a hollow grind where the edges would bite whatever you’re chopping into.

Then the other geometry, like point geometry, if you’re having to us it to piece into something. Rocker. […] kitchen knives I’ll obsess over the rocker. The angle of the handle depending on how tall the person is… for the ergonomics. […] The height thing in particular, I’ll hand somebody who’s like s 5′-5″ one knife and they go, “this is terrible!” Then I’ll hand them another one and they’ll say, “this is fantastic!” Exactly the same blade geometry, but the only difference is the angle of the handle.

Why has Kydex taken off in the knife and tactical world?

One is cost. And time. Leather takes a little bit more time. […] I’ve lost knives. […] We were soaking wet and my leather sheath got so soft that the knife just fell out. I don’t have to worry about that with Kydex.

The leather costs more than the Kydex by four fold. […] Kydex is fast; I can make a good sheath in 15 minutes. […] A good leather one […] that can take me four hours.

Is it true that leather can hold dirt and debris that damages the gun or knife while Kydex doesn’t

Generally with leather, where people let the stuff get a little bit wet and then the salts come out of the leather… cause damage to the material [metal]… I see that more often than any kind of debris or detritus that would have been in the sheath or the holster.

If you take care of it and you don’t store it in it, leather is just great. You can get abrasive material in either or. It’s maintenance. You have to clean and oil your leather. You have to clean your Kydex sheaths and holsters.

What is the learning curve on working with Kydex?

Kydex is pretty straight forward. […] Kydex is the trade name; there are a lot of thermally moldable pastics you can get. […] You get the sheet from the manufacturer and it’ll tell you what the working temperature is. Basically you heat it up to it’s working temperature. And you do it gradually. And then […] with a vacum press or a foam press […] you compress the plastic over whatever it is you want to form it to. Once it cools down it’s in that shape. […] Then cut […] and put grommets/rivets in it. […] Grind the edges. Buff it. Then you’re done, really. […] You may have to relax it a little with a heat gun.

What tools do you need for making things with Kydex?

  • Something to cut it on.
  • A box cutter.
  • A hand drill.
  • Appropriate size drill bits for the grommets you’ll use.
  • Grommet set.
  • Buffer
  • Grinder
  • Something to heat it up on.
  • A hot gun [digital infrared thermometer]
  • Foam and build your on press.

Special Note:

The final episode of this season, season 5, will be on May 25. ITRH will return August 1st for Season 6. You will be getting the now traditional summer shorts episodes roughly every three weeks while the show is on summer break.

Resources for Knife Making and Kydex Making:

In his free time, he enjoys hogging the remote, surfing, scotch, mental masturbation and debate over philosophical topics, and shooting stuff--usually not all at the same time.

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