StarDestroyer.Net BBS

Yes, I know Velvet Assassin sucked.

But when I saw that knife, I said to myself "I must have one!" I shopped around but came back with nothing. I don't like ordering off the net because I like to be able to see the knife for myself first, but after looking around and finding replicas made by Windlass Steelcrafts and some others, I found some prints on Wikipedia.
http://en.wikipedia.org/wiki/File:Fmfrp_12_80_p69.png

The problem that comes to mind when looking at this design is the rat-tail tang - the blade tapers down to a tang about one eighth inch in diameter, running through a hole drilled through the handle. The pommel nut is then screwed on to press the handle against the guard, and the guard supports the blade. My guess is that they did this because it eliminates the need for handle scales and very precise fits, so making them would be a bit easier. Unfortunately I have a bit of a thing against rat tails, especially the way this one's constructed - if the pommel nut was ever to loosen, that would make the tang flex under stress because the grip and guard aren't able to support the blade as well, and the blade could break.

So, using NX to do the models and Inventor to do the renderings, I'm working on my own version of the Fairbairn-Sykes fighting knife, and this is what it looks like, currently.

http://i245.photobucket.com/albums/gg62 ... sykes1.jpg
http://i245.photobucket.com/albums/gg62 ... sykes2.jpg
http://i245.photobucket.com/albums/gg62 ... sykes3.jpg

Here I've removed one of the scales so the tang is visible.
http://i245.photobucket.com/albums/gg62 ... sykes4.jpg

My design would be a bit more complicated to make, requiring tighter tolerances, more finishing, and possibly precise grinding, but it completely eliminates the rat-tail tang. Because the blade doesn't depend on the grip and guard and is fixed in place on a more robust tang, it's going to be a lot stronger.

Material information is tentatively set at:
Blade and Guard: 420 J2 Stainless Steel
Handle: C464 Brass (I might change this to Gaboon ebony or African mahogany, and then attach a brass pommel to the end, we'll see. Currently it's still all ideas.)
Retaining Pins: SAE 15-5 Stainless Steel (These are not shown)

The guard is to be brazed onto the blade before the handle scales are fitted. They will be held in place by a pair of stainless steel pins that will be shrink-fitted. If I go with wood scales instead of metal ones, I'll probably need to glue them down in addition to putting in the pins. The last option are screws but I don't like that.

The brass handles will be powder-coated black. I chose stainless steel for rust resistance, and also for the added beauty of the blade. Because the cut of the saw would cause the scales to not line up if I simply turned them on a lathe and cut the result in half, I'll cut two sets of scales, keep a bit of excess, then mill them down until they match up perfectly. Wasteful, but hey, the product comes first.

If I can book any time on our CNCs and some time in the shop this upcoming school semester, I will see if I can make one, or a couple. The blades I'll probably need to make by hand, so this will be an interesting learning experience.

Fully dimensioned engineering drawings will be released once I finalize the designs. So far, what do you think?

If the knife is actually going to be used, then a better steel than 420J2 is needed for the blade. 420J2 is butter soft and has next to no wear resistance, it won't take a crisp edge and any edge you manage to put on it will dull very quickly with use. Use 420HC at a minimum if corrosion resistance is needed, 440B & 440C are also good choices depending on how much hardness & corrosion resistance you need. 440C is harder & more wear resistant but it doesn't resist rust as well as 440B.

If you don't need a stainless steel, then O1, A2, A8, and 5160 are all good choices. They're tougher, harder, and will take more abuse than stainless, but they'll rust if you don't keep them dry.

I guess so, Aerius; if I'll be slapping wood handles on this it'd probably take away the ability to resist rust like 420J2 is so great for. I briefly considered 4340 Alloy after reading your post, but I didn't think it'd be worth the extra money, and it isn't available in flat bar at the place I go to for metal, meaning I'd have to order it in, and that assumes they even make it in flat bar.

Yeah - I reconsidered brass handles. They'd be quite heavy and brass is very expensive right now. Because of the amount of waste of cutting the scales like that, I redid the way the scales are fitted to the blade. This cuts down on waste quite a bit.

I added a slight chamfer to the guard.

http://i245.photobucket.com/albums/gg62 ... AD/fs3.jpg
http://i245.photobucket.com/albums/gg62 ... AD/fs2.jpg
The scales are now asymmetric. This will allow me to simply mill a slot through one using a half-inch cutter, and then turn a smaller one on a lathe, cut it in half, and fit it overtop. This should reduce waste material by about a quarter, if I'm careful and don't need too much extra stock on the lathe.

This is with both scales removed. You can see the pins and the pommel spike.
http://i245.photobucket.com/albums/gg62 ... 4metal.jpg

And fully assembled.
http://i245.photobucket.com/albums/gg62 ... AD/fs1.jpg

http://i245.photobucket.com/albums/gg62 ... erhead.jpg
I made the point of the blade a bit more rounded than the original designs called for - it's actually parabolic. The idea was to provide a bit more support there.

The curve of the handle looks a bit off, I guess it might've been my mistake when I transcribed this. I'm going to try updating that and make it a bit thicker near the pommel, like the originals.

Davey wrote:I guess so, Aerius; if I'll be slapping wood handles on this it'd probably take away the ability to resist rust like 420J2 is so great for. I briefly considered 4340 Alloy after reading your post, but I didn't think it'd be worth the extra money, and it isn't available in flat bar at the place I go to for metal, meaning I'd have to order it in, and that assumes they even make it in flat bar.

Corrosion resistance isn't an issue with wood handles since in any decent knife design, the wood is glued to the steel with a generous amount of epoxy. This seals the metal and prevents moisture from getting under the wood and rusting it from the inside. Also, 4340 is a structural steel for stuff like engine crankshafts & aircraft landing gear, it's not for knives, the material properties are all wrong. For knives you're looking at tool steels for the most part, meaning steels that are used to make drill bits, saw blades and other such cutting instruments.

I made the point of the blade a bit more rounded than the original designs called for - it's actually parabolic. The idea was to provide a bit more support there.

The problem there is the knife now becomes a crappy stabbing weapon, and you'll actually do more damage to the tip when stabbing since it won't penetrate cleanly. If you stab a parabolic tip into a block of wood there's a good chance you'll bend it if your aim isn't straight and you don't hit it cleanly. A sharp point will penetrate even if your aim is off and the rest of the blade follows it in, round it off and the tip tends to glance before sinking in which puts a lot more stress on it and rolls the tip over or bends it. The other issue then is it won't penetrate through heavy fabric such as a couple layers of heavy denim or a leather jacket. For a stab to get through it needs a sharp point, and if you use a good steel you can stab it though car doors without damaging the tip.


If the knife's going to be a display model, then go ahead and make it out of 420J2 and grind it in whatever shape you please. But if it's actually going to be used as a practical tool, then you need to take function into account, that means material choice, blade geometry, weight distribution, and all that other stuff become important.

1095 should be a great and common steel to use in a knife (you'll find it in Ka-Bars), but it's very high carbon, and so will rust easily. You might want to try AUS-8 instead of 440C as welll, since it's more rust-resistant (and my Boker held its edge for quite a while, so the hardness isn't bad). Certainly they're not ATS-34 or anything, but you get what you pay for.

The changes you made would definitely provide an improvement, yes. Remember that W. E. stressed the importance of using all parts of the knife, including the pommel as weapons, so the tougher, the better.

Ack - didn't think about that with the point. Oversight on my part.

I've changed the point back to the sharp point in the original drawings and I made those changes with the handle. How's this?
http://i245.photobucket.com/albums/gg62 ... /CAD/5.png

Also, 4340 is a structural steel for stuff like engine crankshafts & aircraft landing gear, it's not for knives, the material properties are all wrong. For knives you're looking at tool steels for the most part, meaning steels that are used to make drill bits, saw blades and other such cutting instruments.

Yeah, I was thinking about recarburizing it using a bag and charcoal before the final quenching to raise its carbon content - I've been able to get samples of 1040 to around 60 Rockwell-C before on the surface (although the results have been terribly inconsistent, but that's my probably own fault for not using enough charcoal dust or not always packing it in right...) Ah well. You're right.

Here are the rest of the shots.
http://i245.photobucket.com/albums/gg62 ... /CAD/1.png
http://i245.photobucket.com/albums/gg62 ... /CAD/2.png
http://i245.photobucket.com/albums/gg62 ... /CAD/3.png
http://i245.photobucket.com/albums/gg62 ... /CAD/4.png

1095 should be a great and common steel to use in a knife (you'll find it in Ka-Bars), but it's very high carbon, and so will rust easily.

Yeah, I guess so. Might as well, I definitely could afford to lavish some maintenance on this blade, if I could make one. I guess it'd also be easier to work than stainless, so that's a plus.

The changes you made would definitely provide an improvement, yes. Remember that W. E. stressed the importance of using all parts of the knife, including the pommel as weapons, so the tougher, the better.

Thanks. I added a spike to the pommel of one of my lightsaber designs: I've seen guys at a European Martial arts centre fight using fifteenth-century two-handed swords and it surprised me how much the other parts of the sword are used offensively - the crossguard and pommel, I mean. Some of the modern Fairbairn Sykes knife makers have similar pommels, so I figured I might as well tack on my own.

The advice is appreciated, guys. Thanks.

I missed something big in the earlier models, but now that I have a good view of the handle I see a big problem. As far as I can tell the handle as a whole is round and made of nice smooth wood, this is fine if the knife's going to be used for stabbing, but for slashes, it's bad. If the edge doesn't contact squarly in a slash, the knife's going to twist in your hand and stop cutting, or if it's a hard enough impact it's spin right out of your grip. If you're going to keep a round handle, it'll need a heavily checkered or textured grip such as this so it stays locked in position in your hand even if your hands are sweaty, wet, or covered in blood. Personally I'd suggest going to an oval cross-section on the handle so it indexes in your hand better, that way you always know where the edge is even without looking. I'd still use some kind of texturing on the handle to further improve the grip.

With regards to steels, anything with less than 0.5% carbon is going to be useless, it just won't harden enough unless carburized or otherwise case-hardened. Problem there is as soon as you sharpen the knife a few times, the hardened layer is gone and you're into the softer metal. Plus you still need to temper the steel after quenching & hardening so the final hardness is going to end up too low.

1075 is probably the best one to start with, it should be fairly cheap and it's about the easiest one to heat treat and temper. O1 tool steel is also very forgiving to work with. 1095 needs faster quenching to get good hardness, problem here is unless you have special equipment, the only way of doing this is a water or brine quench which results in more warpage in the blade and possible cracking if you're unlucky. You can find material datasheets and guides for heat treating & tempering the steels all over then internet. Here's one for O1.

One more thing. You want to do all your rough grinding and machining before you heat treat the steel, otherwise it's going to take you ages to get anywhere. Once the steel is hardened it's almost impossible to drill and it'll laugh at saw blades. Files will just slide off it and it'll wear out sanding belts real fast.

Gotcha. An oval cross section would be somewhat difficult for me to do very consistently on only a lathe, but I could knurl or checker the grips pretty easily. If worse does come to worst I could wrap the grips in nylon para-cord, glue it down, and do a diamond patterning on the wrap overtop to give it some ovality.

Thanks for the tip about 1095, I'm pretty sure I could order in some 1075 carbon steel or O1 tool steel, or I may have some stock lying around here *somewhere.* I'm fairly competent with machine tools, but I haven't made any knives before, so I suppose if it's easier to work, even better.

Here's the drawing for the blade. It hasn't been backdrafted yet so there could be a number of missing or superfluous dimensions, I'll iron them out as I go. The title block is somewhat minimalist, I don't have any more-professional-looking patterns made at the moment, so I quickly drew one up that'll serve the purpose. Ignore the notes in the lower-left corner for now.

http://i245.photobucket.com/albums/gg62 ... lade-1.jpg

To make ovalized handles, you could start it off as a round on a lathe, then flatten it out and do the final shaping on a belt sander. Ideally you should use a slack belt sander something like this one where you can hold the piece against the free part of the belt and let that make a nice curve for you. It's possible to do it on a normal belt sander, you just need to take a bit more care so you don't get flat spots.

aerius wrote:<TRUNCATED>something like this one where you can hold the piece against the free part of the belt and let that make a nice curve for you. <TRUNCATED>

Brilliant. Thanks man. Damn, why didn't I think of that...

This is coming along nicely. I'll try to see if I can model that in NX as well.