Why Ti for liners?

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fishbulb

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Sep 18, 2001
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I've noticed that many high-end folders use titanium instead of stainless steel for the liners. From my understanding of the materials' properties I can't see what the benefit of doing so is, and I'm looking for some suggestions.

The primary benefits that Ti has over stainless is that it is lighter for a given volume, has a higher strength/weight ratio, and is effectively immune to corrosion. While in some applications these benefits are really critical, I can't quite see what the real advantage is when used as a liner in a folding knife. To look at them one by one:

Lighter
While a Ti liner will indeed be lighter than a steel liner of identical dimensions, the actual difference is miniscule. For example, a Ti (density .16 lb/in^3) liner that is 3.5 inches X 1.0 inches X .065 inches would weigh about .58 ounces. A steel (density .28 lb/in^3) liner of the same dimensions would weigh 1.02 ounces. Assuming that you ahve two of these liners the total weight saved by switching to Ti would be just over an ounce. If you take into account that steel liners are often skeletonized to further reduce weight then this difference becomes even less.

Stronger
Although pound for pound Ti is considerably stronger than steel, the limiting factor in a pocket knife is not weight, it is size. It would be difficult (perhaps impossible) to detect an extra ounce of weight, but another sixteenth of an inch of thickness makes a big difference in an EDC.

When dealing with identical volumes as you would be with knife liners steel is a good deal stronger than Titanium, and therefore less likely to fail. Some people seem to think that by getting Ti liners they are getting a stronger knife, when in fact they are not.

Corrosion resistant
While this does make sense on a knife that has a Talonite or Titanium blade, it seems odd to tout the corrosion resistant properties of a Ti handle when it is attached to a steel that is not particularly corrosion resistant. Even the 440 or AUS series stainless steels will readily rust if given the chance, so it is hard to understand how having a corrosion resistant handle is a major benefit.

There are also a number of drawbacks with Titanium. It is expensive, much more difficult to machine than stainless, and considerably more subject to wear due to rubbing on the blade tang.

It would seem that with the possible exception of some very specific uses stainless is a generally superior material for usage in knife liners. I would greatly appreciate any input as to why Ti is used as frequently as it is.
 
I've heard that titanium is preferred for liners because it is sticky. The liner sticks to the tang which enhances the lock.
 
Originally posted by anthony cheeseboro
I've heard that titanium is preferred for liners because it is sticky. The liner sticks to the tang which enhances the lock.
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I've heard this too. But you could do the same thing by putting a Titanium tip onto the liner lock right? So if thats the case I agree with fishbulb.

I've also heard that Titanium has more memory...So it would retain the "bend" in the liner on the lock side easier...But steel seems to do it fine, so I don't know how important this is.
-Kevin
 
You problley dont want to know the truth but its quite simply this Ti is "Hot" Like tallonite stellite and ect No one uses stainless because it doesnt sell people want to say "oh yea this has a Talonite blade Ti liners Carbon fiber scales" and so on So the Demand for the name is what keeps Ti being used and thats about it
 
Titanium liners can be a good thing when living and working in a humid environment. You don't have to worry about rust developing inside the handle or under the scales. On the other hand, titanium linerlocks wear faster than steel linerlocks.
 
Originally posted by Cosmic Superchunk
Titanium liners can be a good thing when living and working in a humid environment. You don't have to worry about rust developing inside the handle or under the scales. On the other hand, titanium linerlocks wear faster than steel linerlocks.
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420 liners aren't going to rust really though either. Titanium liners don't rust...but the blade inside the hanle will unless its talonite, H1, etc.
-Kevin
 
I've heard that Ti has a "galling" effect when used on a frame lock which makes it more secure. Personally I've never really seen this effect on a liner lock. I would guess that it would be more noticeable on a frame lock because you can apply pressure in excess of the "spring" in the lock. If the lock is properly designed it shouldn't be a factor regardless of material choice.

I believe that Ti actually has less memory than steel, and is not as well suited to applications as a spring. Generally speaking, springs are made of steel in virtually every application in which they are used.

I strongly suspected that the primary appeal was just as bryce said, a way to gain a marketing advantage by capitalizing on the "space-age" appeal of Ti. Makes you wonder what other heavily promoted features in the industry are just hype as well.
 
Makes you wonder what other heavily promoted features in the industry are just hype as well.
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I agree about Ti being hype...and as for heavily promoted features of the same type...lets just say I can name a few. :p
-Kevin
 
I think some of your points are a little off:

Weight First, skeletonizing would increase machining costs. Second, in a 5 oz. knife, 1 oz more or less will make a big difference in overall weight and balance.

Strength For a 25% decrease in weight, 50% thicker liners can be used. This creates a 69% increase in stiffness (my crude remembrances of beam theory gives the equation (.5 * 1.5^3) - 1 * 100% ). 1/16 of an inch makes a difference, but so does 0.5 oz. of weight.

Corrosion resistance Liners, by their very nature are difficult to keep clean. With my SAK knives, I don't have any blades with rust, but several of the SAK liners have developed spots of rust.

Of course, the "cool" factor also looms quite large. I have a Titanium micro-pry bar+bottle opener made by R.W. Clark and I like it because it is light, stiff and just plain "cool".

edit: clarified SAK blade vs. liner rust statement. Corrected stiffness increase from 70%.
 
I have a couple of folders that weigh in the 1.0 to 1.6 oz range, so the weight difference would be considerable.
 
I have two kershaws with Ti liners the 1500 and 1510 and the 1550 blackout has steel liners and the little chive 1600blk.Of the four perception-wise the chive feels the heaviest due to its frame lock construction of 420 stainless steel. The weights range from a low of 1.9 oz to 3.5 for the blackout with the two Ti Linered knves in the middle. I feel that the chive with Ti frame would be a VERY light unit the estimated weight would be .9 oz or less and that would be a very weird thing. To give you an idea of what 1 ounce feels like take 9 American pennies in your hand;that is 1 ounce.The heaviest is the blackout with the poly handles and steel liners. The random and mini tasks both have g-10 handles and Ti liners and hit the scales at 3.3 and 2.3 respectivly. Lightest is the chive at 1.9 but size to weight puts the chive as the heaviest and it feels it since it has less surface area to distribute the weight over. :cool:
 
Originally posted by enkidu
I think some of your points are a little off:

Weight First, skeletonizing would increase machining costs. Second, in a 5 oz. knife, 1 oz more or less will make a big difference in overall weight and balance.
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Unless I am mistaken, liners are generally blanked out or laser cut. If this is the case then the skeletonizing can be integrated into the original forming operation and there would be little or no cost increase. There is really no way to be sure unless a manufacturer will chip in here, but I would imagine that it is all made in one shot.

Even if it were not the additional cost of machining more holes would be significantly less then the cost of purchasing and forming Ti.

While the addition of 1 oz. is a 20% weight increase on a 5 oz. knife, it is still just an ounce. I would be surprised if somebody could tell the difference between a 5 oz weight and a 6 oz weight without a scale.


Strength For a 25% decrease in weight, 50% thicker liners can be used. This creates a 69% increase in stiffness (my crude remembrances of beam theory gives the equation (.5 * 1.5^3) - 1 * 100% ). 1/16 of an inch makes a difference, but so does 0.5 oz. of weight.
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From what I have seen manufacturers do not take advantage of this. The Ti liners that I have seen are the same thickness as their stainless counterparts (BM AFCK for example) which would represent a significant reduction in strength.

The fact that they use the same dimensions for their steel and Ti liners would indicate to me that they are not real concerned about getting the most out of the material. I would like to see them take better advantage of it.


Corrosion resistance Liners, by their very nature are difficult to keep clean. With my SAK knives, I don't have any blades with rust, but several of the SAK liners have developed spots of rust.
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That is a very good point.

Personally I have never seen a knife which displayed corrosion on the stainless liners in any amount which could cause a problem. Perhaps a few rust spots, but nothing structural. You would likely have to really mistreat the knife over a considerable length of time for this to be an issue.

Gaben: What folders are these? To be that light they would probably have to use rather small liners, in which case the weight difference between steel and Ti would be even less.
 
I've seen Microtech LCC's with rusted liners and backspacers. It is one of the only high end knives that I know off that uses steel liners. I think the Al MAR Sere does too. Since the handle (and liners) are in direct contact with a corrosion friendly environment (human hand)I'd prefer titanium in those hard to clean places.

I have a Spyderco Endura stainless handle that I've carried for a while and it has no rust on it, inside or out. Maybe since it's satin finished it's easier to clean and keep from rusting:confused:

Compare an MT LCC and a Buck Strider folder. The LCC weighs kust as much as the Buck does, but the Buck has thicker liners and a thicker blade. The Strider has TI liners. Maybe Buck sees the light and gives thicker liners because of the weight advantage.
 
posted by Fishbulb:
While the addition of 1 oz. is a 20% weight increase on a 5 oz. knife, it is still just an ounce. I would be surprised if somebody could tell the difference between a 5 oz weight and a 6 oz weight without a scale.
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But the balance will be affected enough to be noticeable.

And of course, for knives where titanium is used for the handle material and not just the liner (like the Sebenza,) titanium can provide a decided advantage in weight.

The fact that they use the same dimensions for their steel and Ti liners would indicate to me that they are not real concerned about getting the most out of the material. I would like to see them take better advantage of it.
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BTW, even a 26% increase in thickness will provide equivalent stiffness. I don't know about you, but I can't tell the difference between 1/16 and 5/64 without a gauge. Maybe they did increase the thickness and we just can't tell. Of course, they probably didn't bother, why increase cost :).

I think we can agree that titanium does have some advantages and some disadvantages when used as knife liners. I think we can also agree that titanium sells well enough to offset the additional costs. And that is the ultimate reason why so many makers are using titanium liners in their knives.

Plus titanium is cool :D
 
Fishbulb,

Your profile says you are an Engineer / Student. You’ve make statements based on very little or incorrect data and discount the real world experiences of others. I’m going to tell on you to your professors. ;) A good engineer should always consider and factor in the experiences of others when developing a hypothesis.

A few facts need to be clarified:

Spring -
You are correct that commercially pure (CP) titanium is not a good spring material. It is soft and gummy. However, I don’t know of a knife made using CP for the liners. Almost all knifemakers and knife factories uses 6AL4V (6% aluminum, 4% vanadium, remainder titanium) which has very good spring properties. You wrote “springs are made of steel in virtually every application in which they are used.” Springs are made of lots of different materials including: steel, wood, thermoplastic, composites, titanium, etc. The reason steel is used for most springs is cost. Many of the non-steel springs have life cycles that exceed steel springs by two times or more. Most stainless steels must be heat treated before they can be used for liners. Titanium does not require heat treatment. Bottom line: titanium does have the required properties to make a good spring on a liner.

Galling -
Titanium is notorious for galling. Its propensity for galling is the reason titanium is so hard to machine. You wrote: “Personally I've never really seen this effect on a liner lock.” Your statement does not mean it does not happen. If you had two identical folders, one with titanium liners and one with stainless liners, I’m sure you would feel the difference when pushing the liner away from the tang. The galling is the little hang or catch before the liner moves. If you want to learn about galling come over to my house and we will put some titanium in machines and play with it.

Manufacturing Costs -
Concerning adding holes to skeletonize the liner and reduce weight you wrote: “Unless I am mistaken, liners are generally blanked out or laser cut.” If liners are fine blanked the cost would be the same as a full liner. However, if the liners are being laser cut the additional time required to cut the weight reducing holes would be significant. I’m familiar with several knife manufacturers. Fine blanking used to be used by almost all the big companies. Fine blanking was cost effective if the company was making the knife by the thousands or more over several years. Now a new knife model may be available for a year and then discontinued. In this case fine blanking is too expensive and laser cutting is cost effective. A knife company that invests in laser cutters is able to respond to customer wants much faster. The cost of laser cutters continues to come down. It us just a matter of time before fine blanking is obsolete. Don’t forget to add the cost and time of heat treating the stainless steel liners. Material cost is not significant. The cost for a pair of liners measuring .050”x4”x1”; titanium $1.10, stainless $0.59, or a difference of 51 cents per knife. Bottom line: To determine if skeletonized stainless steel liners cost less than titanium liners, manufacturing costs must be considered.

Resistance To Wear -
Concerning titanium resistance to wear you wrote “considerably more subject to wear due to rubbing on the blade tang.” This is an interesting issue. A small number of makers say that they have had to replace titanium liners due to wear. Many other makers say they have never or very rarely have had to replace titanium liners. I have never had to replace any of the liners on my factory or custom knives. I do know some makers increase the lock resistance to wear by heating the tip if the liner that engages the tang with a torch until it is red hot. I questioned the hardness of the heat affected titanium until one day when I deeply scratched the VG10 blade of my Spyderco Calypso on the plasma cut edge of titanium sheet. Bottom line: If done correctly titanium liners are resistant to wear.

My Opinions:
Weight -
I can easily feel the weight savings of titanium over stainless steel by hand. Maybe I play with too many knives. Weight is important. The less a knife weighs the more knives you can carry before your pants start to fall down.

Corrosion Resistance -
I think corrosion resistance is very important. The liners (and backspacer) are not as easy accessible as the blade for cleaning so they should be as corrosion resistant as possible. If the liners are stainless steel and skeletonized there are lots of place for junk to collect and start corrosion. I want my knives to last long enough for me to give to my grandkids.

Coloring -
Titanium can be anodized different colors. Stainless steel can be heat colored but it is not as easy or controllable as titanium.

Hype
Sell the sizzle not the steak. Of course there is hype involved with titanium! The name is cool. You can say to people, “My knife has some of the same materials as the SR71, Space Shuttle and F22 Raptor”. The similar condition exists with carbon fiber. CF is miserable stuff to work and a serious health hazard. But it looks great and is a functional material.

Titanium is hyped.

Titanium has properties to back up the hype.

When built correctly titanium makes a good liner for a folding knife.
 
Chuck,
That is about the best reply that I have ever read explaining titanium liners. Thanks.

FWIW, in the many years that titanium liner/framelocks have been coming out of my shop, I've never had to replace a titanium liner for wear or any other reason.
 
Originally posted by Chuck Bybee
Fishbulb,

Your profile says you are an Engineer / Student. You’ve make statements based on very little or incorrect data and discount the real world experiences of others. I’m going to tell on you to your professors. ;) A good engineer should always consider and factor in the experiences of others when developing a hypothesis.
Click to expand...

Actually, I was looking for the real world experiences of others to explain why the makers do what they do. Certainly didn't think that I discounted anybody.

Believe me, nothing frustrates me more than when a co-worker chooses to believe his theories and calculations over the experience of a technician who has worked with the product for decades. Generally I come up with the theoritical work and then go show it to a tech and ask "Does this look right to you?" in order to get a reality check on the designs. It seems to work quite well. This is what I tried to do here. I came up with the theoretical case from the information that I had available and then presented it to a huge experience pool to see how it stood up.

Your post is very informative and was exactly what I have been looking for.


Spring -
You are correct that commercially pure (CP) titanium is not a good spring material. It is soft and gummy. However, I don’t know of a knife made using CP for the liners. Almost all knifemakers and knife factories uses 6AL4V (6% aluminum, 4% vanadium, remainder titanium) which has very good spring properties. You wrote “springs are made of steel in virtually every application in which they are used.” Springs are made of lots of different materials including: steel, wood, thermoplastic, composites, titanium, etc. The reason steel is used for most springs is cost. Many of the non-steel springs have life cycles that exceed steel springs by two times or more. Most stainless steels must be heat treated before they can be used for liners. Titanium does not require heat treatment. Bottom line: titanium does have the required properties to make a good spring on a liner.
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Yes, it can make a good spring for a liner; I never said that it cannot. I was questioning whether it results in a superior spring compared to stainless.


Galling -
Titanium is notorious for galling. Its propensity for galling is the reason titanium is so hard to machine. You wrote: “Personally I've never really seen this effect on a liner lock.” Your statement does not mean it does not happen. If you had two identical folders, one with titanium liners and one with stainless liners, I’m sure you would feel the difference when pushing the liner away from the tang. The galling is the little hang or catch before the liner moves. If you want to learn about galling come over to my house and we will put some titanium in machines and play with it.
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Interesting. The only Ti liner lock I have available right now is a BM 690, and I went and tried the liner a few times. There is indeed a discernable "catch" before the liner moves during unlocking. It is so faint that I never noticed before. I would be curious to see how much this property affects lock security.

I doubt that it would be enough to prevent release when accidentally pressing on the lock, but it could possibly be a benefit in resisting "creep" due to torqueing or vibration. Since most liner lock failures seem to be of the latter kind, this could be quite an advantage.

I do know some makers increase the lock resistance to wear by heating the tip if the liner that engages the tang with a torch until it is red hot. I questioned the hardness of the heat affected titanium until one day when I deeply scratched the VG10 blade of my Spyderco Calypso on the plasma cut edge of titanium sheet. Bottom line: If done correctly titanium liners are resistant to wear.
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The only production company that I know of who torch hardens the contact point of a Ti lock is Chris Reeve. If other manufacturers are taking advantage of this then it is much less of an issue. The Ti liners on the production knives which I have handled did not show any indication of this.

Custom makers were never intended in the scope of my original post. I'm primarily concerned with production companies. Perhaps I should have clarified that earlier.

Coloring -
Titanium can be anodized different colors. Stainless steel can be heat colored but it is not as easy or controllable as titanium.
Click to expand...

Good point. Not much of a functional concern, but I can't imagine the aforementioned 690 without those nice blue liners.



When built correctly titanium makes a good liner for a folding knife.
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Yes, absolutely no doubt that it does. I was questioning whether it makes a better liner than stainless, and if so is this performance increase enough to justify the increased cost.

Thanks for your post, I found it very informative. There are still a few things that I'm curious about regarding manufacturers' choices of liner material, but it certainly seems that the advantages of Ti are more significant than I first believed.
 
I must have numb fingers. I can't feel the "catch" of Ti on the blade of my kershaw 1500 but I can feel it on my 1510 which is basically in an unused condition. Has anyone else found that your EDC w/Ti liners "break in" ? I have never had my 1500s lock release accidently but don't need to find out the hard way! :barf:
 
I do like to have a "catch" with the liner lock spring... if it's not more secure, it makes me feel like the lock is more secure.

I definitely agree: Knives made with steel liners or handles (e.g. Kershaw Vapor) or knives made from a solid steel frame, even if well built (e.g. Sawby Combat Utility Knife) definitely feel much heavier than the Ti framed/lined knives we have grown to know and love.

Ti is a good choice for folders, IMO. Small or large.

The following is offered not to point any fingers what-so-ever, just an observation:

When I got out of college with my fancy schmancy electrical engineering degree, along with wet ears and green horns and all, mercifully I had some humility and was smart enough to know how ignorant I was (ignorant, not stupid).

I learned a TREMENDOUS amount of what I learned about instrumentation and controls from the "locals" at the refinery/petrochem plant... guys who had been eating/breathing this stuff for decades but just never wanted to, or had an opportunity to, go to college. A little humility and an open, curious mind can carry you a much longer way than a sheepskin (I went and got an MBA anyway... try not to hold that against me).

I think the best thing I learned from engineering school was that if you had a problem or an interest, undoubtedly you weren't the first, and there was a book or article out there, somewhere, that could give you a quick education and keep you from making so many unnecessary, experimental mistakes. I.e., taught me, among many other things, to be resourceful (of course, you don't need to go to college to figure that out).
 
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