homemade knife: small fixed blade

I’ve always wanted to make custom knives. When I finally deemed my circular saw blade too dull to use, it seemed like a great opportunity. The steel used in saw blades usually has high enough carbon content to be hardened, so hang on to them! (or mail to me :D). I traced my blade pattern onto the saw blade and rough cut it with an angle grinder.

For the handle I used a scrap piece of hardwood that I’ve had for a while. I think its bloodwood?

don't throw away those old blades!

don’t throw away those old blades!

I wanted to use a small brass plate between the blade and the handle (what is this part called? Its not really a guard, not really a bolster). I didn’t have any brass plate, but this arcade coin I found was perfect for the job after flattening the faces on a belt sander.

not so worthless after all

not so worthless after all

A slot is cut by drilling a line of holes with diameter slightly smaller than the thickness of the blade. The holes slowly become a slot with careful filing.

careful filing

careful filing

The same technique of drilling small holes and filing is used to make the slot for the knife tang. This is considerably trickier due to the depth. You can also grind a hacksaw blade to fit, and use that to enlarge the hole, but it will still take patience.

think of all the character you're building

think of all the character you’re building

roughly shaped parts

roughly shaped parts

To file the bevel on the blade, I used the setup shown below. A file is attached to a sturdy stick of wood by a screw on one end and a clamp on the other (this is the skinny piece of wood laying diagonally in the photo). One end of this stick rests on a perpendicular piece of wood (the orange clamp is touching it). The height of this piece, and its distance from the blade determines the taper angle. The file of course contacts the knife blank. Also, you can see a little angle iron which is preventing the file from wandering too far down the tang.

flat grind jig

flat grind jig

it resembles a knife!

it resembles a knife!

Now we’re ready to heat treat, so I need a forge. I found a propane torch alone let’s too much heat escape and cannot heat evenly. Plus, a simple forge is surprisingly easy to make. There are tons of articles online showing how to make one, so here’s another:

Start with 2 K2300 bricks. They are really soft and easy to shape. I clamped them together and used an already dull spade bit to drill the forge opening hole.

fire bricks

fire bricks

I added a cavity to better contain the heat. One inch of material around the cavity seems to be the internet-recommended insulation thickness.

marking the size of the cavity

marking the size of the cavity

Its really easy to chip away at this stuff with a screwdriver. I also found that a washer was perfect for smoothing out all the screw driver gauge marks.

shaping the cavity

shaping the cavity

I used a 1/2″ spade bit to drill an opening for the torch.

torch entrance

torch entrance

I hear these don’t get too hot, but better safe than sorry. Some steel angle iron is riveted together to make a stand (a welder would have been nicer though!). You can also see, I wrapped the two bricks together using some steel wire. The internet said this was a good idea, since the brick tends to crack over time, and the wire will keep it together. I am assuming the cracks are more a gradual development and less a dramatic failure???

building a base

building a base

Below is the basic setup, although I ended up changing torch heads since the one below didn’t seem to be burning all the propane (I could smell some). I am guessing it needed more air intake? Anyhow, I ended up buying a Benzomatic all-brash Basic Pencil Flame Torch, which has little air intake holes closer to the end of the torch than the one in the photo below. That seems to have done the trick. (Fun fact: that torch was $12.96 at Home Depot, but the same torch WITH a can of propane was only $12.97).

I used a 1/4″ thick piece of scrap steel over the opening, this seems to help retain heat.

forge setup

forge setup

I’m pretty sure I didn’t do the heat treatment well, but from test filing it seems to at least be a little harder than how it started. Anyhow, I cleaned it up with some sand paper til it was shiny again. I was afraid to drill into the tang directly, for fear it would be too hard, so I decided to try and anneal it. It worked for the most part, but I did accidentally overheat the bottom corner of the blade. oh well.

trying to anneal just the tang

trying to anneal just the tang

Next I covered the blade with tape, and epoxied everything together. Some scrap wood and threaded rod make for a great clamp.

waiting for epoxy to cure

waiting for epoxy to cure

When the glue had cured, I drilled two holes for brass pins in the tang, and a 1/4″ hole that will be drilled out for a lanyard. The next part is definitely my favorite – shaping the handle.

start shaping the handle

start shaping the handle

A belt sander is definitely your best friend for shaping the handle. I also used a combination of rasps, files, and sandpaper. You can see below that I didn’t really polish out all the scratch marks from coarser grits, I was just too impatient to get it done. Surprisingly however, I did manage to get it really sharp! Newbies, make note, a razor sharp blade is within your reach! I was able to shave hairs and skive leather with this.

a shiny!

a shiny!

Seems like the secret weapon to a nice edge is a strop. I took a strip of scrap leather, and rubbed some buffing compound on it. You can tie or clamp one end to something sturdy, and hold onto the other end.

deceptively simple secret weapon

deceptively simple secret weapon

yay, homemade tools are the greatest!

14 thoughts on “homemade knife: small fixed blade

  1. Pingback: Make your own homemade knife: small fixed blade « adafruit industries blog

  2. Nice work, certainly better than my first knife! If the steel was too hard to drill to begin with maybe you can try annealing it first then drilling the holes and heat treating the blade after that to avoid getting soft spots from annealing the tang afterwards. Something to keep in mind, some of these circular saws may be made of a steel which can’t be hardened like mild steel if they have carbide teeth, or may be air hardening (i.e. you can’t do it at home easily). It would be best to look for ones that may be older saw blades like the kind that were used for sawing lumber and whatnot. Another option would be to give it a try on some flat ground tool steel or old files.

      • No problem – great stuff on your website by the way! One more thing – for your heat treating forge, lining the brick with something like fire cement may help to get it to temperatures you want for heat treating, since the bare brick tends to absorb alot of heat on its own as opposed to reflecting it back into the chamber. The bricks I find overtime tend to crack from rapid heating and cooling, but that’s inevitable. For something that would last a little longer ceramic wool may be a better bet, but that also needs a coating for refractory .

      • hmm, I think I’m definitely going to give fire cement a try. In addition to the bricks absorbing a lot of heat, there seems to be a gap between the two bricks now, maybe from warping after the first few uses. Sounds like fire cement could help seal that, too. Thanks!

      • Yup, firebrick tends to do that. Just remember to let it dry thoroughly before firing it up and curing it or you’ll end up with large blisters of fire cement. Let us know how that turns out!

  3. Pingback: Choosing A Good Hunting Knife | Hunting Fishing and Wildlife

  4. you can anneal only the place you intend to drill by using a nail in the drill press this will heat a spot very hot softening it for drilling

  5. Pingback: small paring knife | Amy Qian

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s