Optimal use of materials.

[Carlos]

There are a lot of new materials being played with nowadays in knife making, and naturally I wonder if they are being put to the best use.



The new CPM steels, like S90V and 3V designed for corrosion resistance, wear resistance, and toughness, seem like they would be the ideal materials for knife locks -- particularly linerlocks.



What is currently being used for locks? Spyderco mostly uses steel -- presumabley one that maximizes corrosion resistance, but titanium has often been used by others and it seems that its inherent softness has led to many locks wearing out in short order. Would a steel like CPM-3V be an optimal lock material?



I've also been thinking about carbon fibre. While in its primary industrial applications CF is used as a structural material for its light weight and rigidity, in knives it is appears to be mostly decorative. G-10's apparent greater resistance to delamination makes it more desirable for handle scales on "using" knives, but what about the structural advantages of CF? It seems to me that CF would be a great material for backspacers and auxilliary liners (not the lock liner as in linerlocks).



Imagine a liner-locking knife handle of two G10 scales. On the lock side a CPM-3V steel liner is nested into the G10. On the opposite side there is a supporting CF liner (rather than a metal one) bewteen the G10 scale and a CF backspacer.



Would the G10 protect the CF from abrasion and shock, while allowing the handle overall to benefit from additional rigidity from the CF reinforcent, and at a minimal weight penalty? Such a thing might be too expensive to produce, but I wonder if it would provide real world benefit.



Edited by - Carlos on 10/28/00 12:06:08 AM

[sal]

Hi Carlos. the possibilites are many.
good prjects for protos or customs. difficult to do in production. the costs go up and the average ELU would appreciate the novelty.

It would make an interesting knife. What other materials are intriguing?

sal

[Carlos]

Hi Sal,

I guess I'm sort of a "refinements" kind of guy -- I'm always wondering if something could be improved or used in a better way. Actually I've been thinking about G10 as well.

All the advanced composites are really interesting, and G10 seems like it isn't being used to its full potential. Of course, Spyderco has gone the furthest with using the potential of G10 in the handles of the Starmate and Military. It always seemed odd to me that everyone uses steel or titanium to "reinforce" G10, when the laminate itself is supposed to be stiffer and stronger than metals.

One way to improve G10 in use in knife handles would be to switch the fiberglass yarn in the laminate. Most G10 in knife handles seems to be based on generic E-glass (made for electrical insulative applications). S2-glass (made for high strength structural applications), which is stiffer and stronger would make a better base for the laminate in G10 knife handles that attempt to do away with metal "reinforcement." The ELU are dubuious about "unsupported" G10, so it would have to be extremely stiff and strong to be convincing. Most G10 scales seem to be too thin as well, giving an undesirable abount of flex for a strucutral application, which has led to the myth that it needs metal "supports."

I was also thinking about something you said about the strength of knife handles -- it all comes down to the pins/screws that hold the handle together. Speed-tech gets around this by machining its handles out of a single piece of Aluminum. A way to make a G10 handle metal-free in terms of structure (locks aside), would be to have the two G10 scales and a G10 backspacer epoxied together. No pins, no screws -- this works for many CF bicycle frames, and Aluminum frames.

Of course, there would still be a screw for the blade hinge, and the lock - nested linerlock or otherwise - would add some metal content. One might also have to use the same kind of clip that you use on your FRN handles knives. But the epoxied G10 would effectively a single-piece handle.

To make this work you'd probably have to use 6 or 9 weave for the scales and 12 or maybe 20 weave laminate for the spacer (or a double or triple layer sanwdich of 6 or 9 weave), preferably based on S2-glass. There could be no perceptible flex in the handle for ELU confidence reasons, though some would never accept something so radical. But a "solid" G10 handle seems like it would be the next step in the evolution from the Military/Starmate handle.

Something like this would probably be more applicable to production knives (on the higher end of the price scale of course), than my CF-supported idea above.

Edited by - Carlos on 10/28/00 8:51:11 PM

[sal]

Interesting notion Carlos. We build a solid G10 model (Blackhawk) about 7 years ago. Even the spring was made from G10. The only steel was the blade and lock lever. Vince put it together as an experiment.

We send the prototype out to be blackened and the blackening process somehow took the "spring" out of the G10 spring.

One of these days we will again get into an all composite piece.

sal

[Carlos]

Hi Sal,

Wouldn't it have made more sense to use a G10 lock lever and metal spring, or is there some reason that G10 doesn't make a good lock lever?

Was that protoype for the old C24 Blackhawk? (Which reminds me, did the Native Chief get shelved or is it still on the future SKU list? Seems like you're going to have another SKU reduction poll pretty soon <img src="wink.gif" width=15 height=15 align=middle>

[sal]

Hi Carlos. The G10 material will not make a good lock to interface with the tang of the blade. Most of the forces in a lockback go against the lock, the tang or the pins.

G10 does not have the shear strength to interface with the steel tang of the blade. The tang will cut the G10 at too low a poundage for our lock strength requirements.

It might work well in the compression lock because the amount of material that needs to be under compression is very little.

sal

[Carlos]

Thanks for the explanation Sal.

The idea of a composite compression lock is an intriguing one. It quickly brought to mind the notion of a G10 handle with a Carbon Fiber compression lock. :D

CF is often used for things like gears and cams where high shear strength is required. Of course there is a bewildering variety of CF laminates so there are probably more than a few that are optimized for that kind of application.

An &quot;all composite&quot; handle with G10 for the handle and CF for the lock would be very exotic indeed. Do you think it would work?

[sal]

It would take some R&amp;D time for building and testing to be sure and R&amp;D is pretty busy right now. Ultimately, I think long term compression on the composite would take it's toll (molecule by molecule) and vertical play would result. Of cousre one could have a metal lock (1/4&quot; x 1/4&quot<img src="wink.gif" width=15 height=15 align=middle> attached to the composite carrier.

sal

[Carlos]

Sal,

Don't the glass and carbon laminates have greater compression strength than steel, or is the problem one of fatigue?

I was thinking about the way that Kevlar is used in carbon fiber or fiberglass hulls of kayaks and some high-tech racing sailboats. What they do is compose the laminate with an outer layer of fiberglass, and an inner layer of kevlar. When the boat hits something, the external pressure compresses the fiberglass layer (which is its greatest strength), and puts the kevlar layer under tension (its greatest strength).

I guess in a compression type lock, the pressure pushes up against the bar. A laminate bar for the compression lock might best be composed with its bottom layers of kevlar, and its top layers of G10 or CF. That should hold up better over time against fatigue, but I wonder whether it would be stiff enough for a solid lockup from the start. I guess it would take some experimentation to come up with the right proportion of fibers in the laminate -- this is a question for the engineers. <img src="smile.gif" width=15 height=15 align=middle>