What type of steel are lock bars made of.

S

Schroeder Cross-Dunn

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May 7, 2017
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Hi I'm getting interested in making a small frame lock knife,and I'm curious as to what steel i would use for the lock bar. I would assume a spring steel like 5160 but I'm not sure. I'm familiar with blade steels not frame steels! ;) anyway I would appreciate the info.
 
I am not a pro on liner/frame locks, or folders in general by any means, but the lock bar needs to be of similar hardness as the blade to not wear too quickly (not saying the exact same HRC, but both need to be hardenable). More than that, assuming it is hardened and tempered properly, I cant think of any real reason it would matter from a performance standpoint other than corrosion resistance.

As long as it isn't glass hard or (maybe) dead soft, it should never get close to its yield point as it barely needs to deflect, so I would just temper to get the right feel and stiffness in the lock.

I am sure you could use a titanium alloy, but titanium is very tough to machine, so I would stick with steel if possible until I had a good reason to go with titanium.
 
Alright boys, now I clearly need to be educated. Sorry if I gave bad advice, but the only advantages I can see for the titanium are:

1: 45% weight reduction by volume (less by strength).
2: Heat treat not reqd.
3: Corrosion Resistance.

The disadvantages are: It is definitely more difficult to machine. High spring back due to low Youngs Modulus = a lot of chatter. Low thermal conductivity + high reactivity at temp tears up tools. Sure, you can grind it, but but it is much harder to cut. Steel is also much cheaper. And the lock face should be more durable assuming you aren't carburizing (surface hardening) the Ti. Even then, If you picked one of the high abrasion resistance alloys, I suspect that steel would still have the advantage in durability.

What am I missing here (I own a number of steel frame lock knives and have never had a problem with them).
 
Weight and corrosion resistance are the top reasons, but other benefits are no need for heat treatment to act as a spring, and the finishing options with anodizing. Few people want to buy heavy steel frame locks for custom prices. Milling, grinding, laser cutting Ti in my experience isn't much of a challenge. Drilling isn't either with carbide tools or proper technique and hss. Tapping is the only thing that really seems to be difficult with no real way to avoid it's difficulty (as you said, high spring back). Lack of magnetism is inconvenient, it's hard to surface grind on carpet tape because of it's low thermal conductivity.

Carbidizing the lock face is certainly an option and many people do it but I don't find it to be a requirement. The amount of wear occurring on a lock face is pretty low. Proper lock angle will eliminate sticking.

It's not that steel is bad advice and I would encourage anyone making their first frame lock to use steel for the ease and expense if they're not confident their first designs are going to work. Just, like the other guys said, titanium seems to currently be the most common trend that buyers want.

I don't particularly like frame locks and have been making liner locks, but with Ti liners and back spacers. Milling a back spacer to the right thickness, clamping and reclamping since I can't just slap it on a magnet.
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Thanks. Yes, carbidizing, though my iPhone disagrees and insists on correcting to either carburizing or carbonizing.

I think having spent a bunch of time in the military using crap made out of titanium for no good reason at enormous cost to the taxpayer, and having hated working with it because of the spring back. Also, I really hate turning it, and have found drilling to be a pain for the same reason: long, continuous chips. Maybe I need to rejigger cutterhead geometry.
 
Titanium is not prohibitively expensive. We sell blade steel that costs more than 6-4 titanium.

The key to machining titanium is speeds and feeds. We machine 100's of pounds of titanium in Timascus™ every week. It is easy to machine after you get the speeds and feeds correct.

I agree that titanium is a good choice for the reasons that were previously mentioned, great spring properties, corrosion resistance, heat treating not required, less weight and anodizing. Some knifemakers are concerned about the lock face wearing where the titanium rubs against the heat treated steel lock face. Several knifemakers and knife companies are installing a hardened steel insert on the end of the titanium lockbar to rest against the blade. I personally think this is overkill, but when it is well integrated, it does show off the machining abilities of the knifemaker.

Chuck
 
joedhiggins said:
Thanks. Yes, carbidizing, though my iPhone disagrees and insists on correcting to either carburizing or carbonizing.

I think having spent a bunch of time in the military using crap made out of titanium for no good reason at enormous cost to the taxpayer, and having hated working with it because of the spring back. Also, I really hate turning it, and have found drilling to be a pain for the same reason: long, continuous chips. Maybe I need to rejigger cutterhead geometry.
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Or damascus. Or san mai. Or Rex 121. Or mammoth ivory. It's literally what we do yeah? :D
 
kuraki said:
Weight and corrosion resistance are the top reasons, but other benefits are no need for heat treatment to act as a spring, and the finishing options with anodizing. Few people want to buy heavy steel frame locks for custom prices. Milling, grinding, laser cutting Ti in my experience isn't much of a challenge. Drilling isn't either with carbide tools or proper technique and hss. Tapping is the only thing that really seems to be difficult with no real way to avoid it's difficulty (as you said, high spring back). Lack of magnetism is inconvenient, it's hard to surface grind on carpet tape because of it's low thermal conductivity.

Carbidizing the lock face is certainly an option and many people do it but I don't find it to be a requirement. The amount of wear occurring on a lock face is pretty low. Proper lock angle will eliminate sticking.

It's not that steel is bad advice and I would encourage anyone making their first frame lock to use steel for the ease and expense if they're not confident their first designs are going to work. Just, like the other guys said, titanium seems to currently be the most common trend that buyers want.

I don't particularly like frame locks and have been making liner locks, but with Ti liners and back spacers. Milling a back spacer to the right thickness, clamping and reclamping since I can't just slap it on a magnet.
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I’m working on a pair of liner locks right now. Cut on the wrong side of the line for the lock bar, wasted piece. It’s all part of doing business. Mistakes happen.
 
416 or 420 stainless is an option. Perhaps a little easier to machine than Ti, and maybe a little bit cheaper, though you may want to heat treat it to realize its full potential. All things being equal, I'd just as soon go with Ti. While it is technically more "difficult" to machine, it's really not bad with sharp tools and proper feeds and speeds. The worst part for me is tapping small holes, but with the right setup and techniques, this can be done without TOO much of a headache.
 
Wow this got a lot of replies really fast. Thank you all for the input. I'm seeing a lot of people saying go with Ti, so I would ask would any Ti work or is it a specific kind. To be specific I am designing a framelock the size of a leatherman micra that would fit on a keychain. Blade steel is probably going to be an AUS8 or 440C so I would need to know the rockwell of the lock bar material to make it work. Thanks again for the input.
 
Schroeder Cross-Dunn said:
Wow this got a lot of replies really fast. Thank you all for the input. I'm seeing a lot of people saying go with Ti, so I would ask would any Ti work or is it a specific kind. To be specific I am designing a framelock the size of a leatherman micra that would fit on a keychain. Blade steel is probably going to be an AUS8 or 440C so I would need to know the rockwell of the lock bar material to make it work. Thanks again for the input.
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6al-4v (grade 5) titanium is the most commonly used and available. I think people worry about "hardness" way more than is necessary. For a smaller blade as you describe, it's even less of an issue, as you shouldn't be seeing the kinds of forces that would even begin to deform a lock face. I think a hardened stop pin is more important, especially if you tend to flick your knives open, but the bigger problem with Ti is lock stick/galling, which can be mitigated some by proper geometry, polishing the mating surfaces (again, proper geometry is imperitive), and possibly carbidizing the lock face on the ti side. As mentioned, hardened inserts can also be used, but that's overkill IMO, especially for a first knife. A smaller knife may be difficult enough, in and of itself.
 
Titanium works just fine with our standard knifemaker tools. I find that it cuts, grinds and sands quite easily.

And as far as tapping....with a tap-matic, I can tap 10 holes in about 40 seconds. I've only ever used 1 tap since I got it. Tapped literally hundreds of holes and its still going strong.
 
J. Doyle said:
Titanium works just fine with our standard knifemaker tools. I find that it cuts, grinds and sands quite easily.

And as far as tapping....with a tap-matic, I can tap 10 holes in about 40 seconds. I've only ever used 1 tap since I got it. Tapped literally hundreds of holes and its still going strong.
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I just snagged a micro sized one on Ebay. I'm all about 2-56 holes but I'm still a little sheepish about putting my one remaining 0-80 in there at 400 rpm :eek:
 
It can be cut on a porta-band it's slow and steady no need to ruin the teeth. It can be hand tapped but suggest using a hand tapping guide with those micro taps. Check Little Machine Shop they have the best price on tappers I can't build one that cheap!!!

I have set up a dedicated table top drill press with a Tap-Matic Only for tapping small holes. Yeah it's pricey to set up but if you are doing lots of folder work sure is nice drilling all those tiny holes and the taps seem to last forever.
 
Kevin McGovern said:
So how hard is it to hand tap, and can it be cut on a portaband?
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Porta-band will cut just fine, though it is a bit gummy. I normally use a slow speed with a little bit of cutting fluid to keep the ti from sticking in the teeth as bad. As for hand tapping, thin isn't as bad, though framelock thickness can be a little grabby on the taps. I've had luck with drilling one bit size larger or so, though I'm sure a better tap or different tapping fluid might have helped. The nice thing about breaking taps in titanium is that you can dissolve them in acid without hurting the Ti.
That said, it's obviously better if you can get buy without breaking one in the first place. ;)
 
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