Tanto

Project: Autumn 2023

Writeup: December 2023

No curves allowed...

Let me be the first to say that in general this isn't a particularly good knife. Either in terms of practicality, design or execution. But for me, it's pretty good, and there are a couple of interesting points I thought it was worth showing.

I'm referring to it as a "Tanto" simply because it uses the tip shape which has taken on that name in modern use. Similarities between this design to actual Japanese tanto extend to them both being made out of metal.

If you listen carefully you can hear the sound of all the engineers in the room throwing up

It's actually the first knife I can truly say is completely my own design (as you can probably tell...). Usually I copy and modify stuff from other people. But I wanted to try and get my head around parametric design, so thought I'd pick a little easy 2D project to start off with. So there! The goal of this project wasn't actually to build a practical, well-designed or well-executed knife all along, it was a learning experience! (he says post-rationalising poor decisions...)

I did actually enjoy this part of the process. It was very handy to be able to rapidly experiment with various shapes and sizes in real-world dimensions. Once the parametric design process clicked, it was a lot of fun to quickly change things around to keep improving. I can imagine combining this with some kind of 3D printing / CNC process to quickly translate the designs into something you can hold in your hand for reference would be extremely useful. I was constantly holding a ruler while doing this to try and get that translation but even doing that, 200mm seemed a lot longer in real life.

I originally had a fuller kinda thing going along the flat section above the bevel, but I realised I can't actually manufacture that. But leaving it plain looked stupid, so I added the three bevelled holes just above the guard. I think they look cool in person, but it's obviously completely impractical to have big weak points right at the already weakest point of your tool. If I do another one I'll try and think of something less braindead.

#precision

Cutting out the blank was easy with the design printed out (but next time remember to put the center marks on all the holes idiot). I even remembered to drill the hole that would eventually turn into the sharpening choil!

The bevels were cut using my trusty "file attached to a stick" jig. But the angles actually ended up matching the plans perfectly and the lines were nice and crisp (for me), so everything was apparently good enough! The screw sticking up in the middle of the blade is my stop to help me get a nice straight plunge, which also came out ok.

Brass 'n' Fibre

I had the brass and carbon-fibre in mind ever since the surprising success of the similar design of my T15 Mule Scales which used green G10 as the liners. I also wanted to see if I could do the integrated guard kinda thing by brazing a fat bit of brass on top of the liners. This turned out to work well enough. I thought it would be smart to put two little bits of braze rod physically between the two pieces and then heat everything up, thinking that it would just wick together perfectly leaving no joint. But I ended up needing to squeeze the two piece together as I heated which left a bit of an inconsistent gap which was bigger than I ideally wanted. Maybe more even heat or better flux would make this work, or maybe just having the pieces flush to start with and then adding braze to the outside of the joint to let it wick in would be the way to go.

Then the carbon-fibre pieces were epoxied on before I finished off the profile. This would be much easier with a bandsaw! Took a long time to get everything matching.

Most of the bevels around the scales were done by sticking my tiny belt sander at the right angle and freehanding around the carbon-fibre. But all the internal corners had to be done by hand. Was a bit of a faff, but I was relatively happy.

Deconstructed

In this photo you can see how the scales fit on to the blade with custom bolts. I take 5mm wide M4 connectors and Locktite them onto one set of screws then cut them to the correct length to form the female bolts which register the scales on the blade. Then the male bolts are cut to the right length (you want as many threads as possible but don't want to bottom-out in the threaded part) and everything goes together nicely. I could only find brass countersunk bolts with Phillips heads which look mildly stupid, but they fit together well.

This is also after the blade was hand sanded to 800 grid, acid etched in ferric-chloride and then stonewashed with the world's least consistent garden rocks. The handle scales were similarly sanded, then dunked in cold-blue solution to darken the brass. Then they got stonewashed too to give the brass the same look as the blade.

A close-up of where the blade would snap in half if you ever tried to use it for anything serious...

I was happy with the finish, but it could probably be better if I used some consistent (maybe bigger?) stone media and a nice big tumbler instead of me shaking stuff in a bottle like a chimpanzee. I did mask off the carbon fibre for this, but it might not have been necessary. It might also look better if I left the brass un-etched which would leave it brighter and a better contrast to the dark blade.

Welcome to Greytown USA

Finished it up with another Kydex sheath. It's a bit of an awkward shape, so I wasn't sure about the designs. Maybe a "taco" style would be better? Also it's too tight. My first one was too loose, so the next one is on track to be perfect...

Blade performance is... fine. Geometry is good! But the edge-retention is underwhelming: I've done better with 1095. I think potentially my quench tank (paint pot) wasn't quite big enough so my cooling wasn't as quick as it usually is with smaller blades. The next one will be better. I should also really start experiments with a better steel.