Steel choice for lockpicks...(why emphasis on stainless?)

[krept]

Hope this doesn't come across as being too wordy or abraisive and I apologize if this has been covered in depth by other posts in the past.

What advantages besides corrosion resistance does stainless steel offer for making picks?

I am a hobby knifemaker and have been studying steels for a couple years. I've also got some interested in firearms, which is somewhat related because they use springs... and when you have to bet your hide on a spring, you don't want it to fail.

My understanding is that when chromium is added to steel to make it stainless, it makes the heat treatment including tempering much, much more difficult. Simple carbon steels that range from .18 to .95% carbon is what I believe they usually use for springs.

Stainless steel... as in the literal definition... I believe means that there is upwards of 8-12% chromium in the alloy. The more chromium the steel has, the higher it's stain resistance will be.

When making knives, the composition of carbon is extremely important in the sense that with too little carbon (generally .4% and below) the knife will not have as keen an edge and chances are it will not harden to a good enough Rockwell to make a good blade.

When you run into higher carbon steels, like .8% and above, you run the risk of making the blade brittle, meaning it will break instead of bend or deform under stress. This problem is magnified with a poor heat treat.

Now, bringing this back to lockpicks...

Being totally new to lockpicks, but not steel, it would appear to me that a simple midrange carbon steel would be best suited. Simple steels in this carbon range can be diferentially treated in such a way to make certain parts hard (sometimes to 62RC) or very springy. The advantage to having a hard pick would be that it does not deform as readily, although it could very well break (worst case scenario?). Having a springy pick means that while it would bend, it would be tough and probably give good feedback.

If some corrosion resistance were to be desired, perhaps a steel like 5160 might be a good compromise... it's what the automobile industry commonly uses in truck or car springs. I've made a couple knife outlines from it and while it does rust if severly neglected, it does not rust as much as simple carbon steels.

So... what I'm wondering after all this, is... is there a reason why stainless steel seems to be emphasized in the industry? In knifemaking, it provides almost no advantage other than not corroding as fast. This advantage comes at a cost, however, because stainless steel is frequently brittle when you have long pieces relative to their width. Case in point with this is the use of stainless steel for swords. This is only done usually by low to mid end manufacturers (have you seen the QVC vid of the guy snapping a sword?) because at that length, swords DO commonly snap.

I'd think that this would also translate over to lockpicks because they are long and thin. Because the heat treatment of steel is SO critical, with stainless, you have a tradeoff... if you err on the side of toughness (springy) you sacrifice hardness much moreso than a simple carbon steel... i.e. a simple steel will be as tough (resisting breakage) as a stainless, but will have a higher hardness (resist deformation).

Again... I'm new and I'm sorry if this has been covered or there is another aspect that I haven't thought of regarding the use of stainless steel for lockpicks. BTW... simple carbon steels will polish very, very well. With simple maintenance (keep em dry and wipe them over once with a good rust inhibitor) the shine will remain.

Cheers,
Erik

[Chucklz]

Its for the advertizing appeal. You get to say something like "corrision resistant gov't quality stainless" Some of my favorite picks are made from carbon steel. While I have yet to try the Falle set, I haven't been too impressed with the stainless offerings from SO.

[jordyh]

I guess having the stainless steel ones helps a bit for the lockies, imagine having so many jobs out in the rain that your picks rust on you.

Aside from that, it's probably all trying to get a Unique Selling Proposition as a manufacturer (or it was, a while ago).

[CPLP]

I'm in a project of making na car and I can tell you that carbon steel is much better than spring steel but it's much more expensive. I use hacksaw blades (cheap ones) or any other kind of material that comes cheap. When I buy picks I try to buy the best there is but while making them... I go for the cheaper. For a good rockwell you could use a 154-CM steel, but that's a matter of choice. Usually we go for the higher quality at the lowest price.That's wy spring steel is very used.

[SFGOON]

So good to have a knowledgeable metallurgist aboard.

A great deal of the decision regarding "which metal to use" for lockpicks relates to manufacturing costs, both the materiels themselves and the process of mass producing the picks. Because lockpicking is not a high stress application (at least not for the metal ) a wide variety of metals are suitable. Also, being corrosion-resistant aids in the longetivity of the tools.

[Shrub]

Stainless, without trying you end up with a hard wearing (relative) god looking tool that doesnt need looking after, doest get damaged by work hardening when made, stronger o the thinner sizes, cheaper produce tools from due to methds of cutting etc etc

If you was to make a pick from stainless you are much less likely to then have to heat treat it which requires power and labour and also has the potential of a odd batch here and there getting scrapped due to a power failure or machine down time.

There are pros and cons for any material, its the balence between all those pros and cons that the manufactures have to juggle.

On another point, i thought a big reason for knifes made from stainless were not that they dont rust but more that they can get a sharper edge, are more hygenic and look a lot nicer.

[pretender]

explain the balance stuff, if you would. don't really care for extensive crazy research, just yer stance.

anyhoo, as i recall, stainless didn't really like taking a great edge and it wasn't that effective overall for blades one way or the other. carbon steel remains the champ in that respect, unless i really, really got outshined by technology.

don't often recall a great edge from a stainless blade in my own lifetime. they're hell on wheels.

stainless, as i recall, is hard - either you stamp it cheap and thin or you break out machining and suffer a profit cut. most tend to be pretty inferior in feel, nevermind the look.

just my thoughts, don't shoot me, anyone.

[Shrub]

Ask a surgeon what material his scalpels are made from.

[illusion]

I don't doubt they can be made sharp, but I am not sure about it's ability to keep a sharp edge... it all depends upon the function the blade is expected to fullfill... scalpels are not re-used in general, and this leads me to believe stainless won't hold a decent edge long.

[krept]

good, insightful posts. I appreciate it. Two things I didn't consider: the volume of work that a locksmith goes through and the fact that picks normally don't face the amount of abuse required to deform the metal. In simply going over the little amount of knowledge, I seem to remember some plungers in locks are made out of brass, which isn't that hard relatively speaking.

Regarding scalpels, I figure that they are stainless because simple carbon steels like the 10xx series will rust... fast. I mean if you grind barstock, dip it in normal water to cool it and leave it out for a short period of time it will rust. Oxidization of iron (rusting) is probably something you don't want in the bloodstream. Scalpels and razors are also made very, very thin so they can slice very well. Actually, some of the best scalpels (like those used for some eye surgery) are made from obsidian, but for our purposes (and knives) it's simply too brittle.

As a slight digression, I had to laugh at the marketing angle... the term "surgical stainless steel" is thrown around a lot and that is clearly an example of marketing at work. People associate "surgical" with scalpel and therefore the $4.99 blade MUST be sharp... haha

Just a brief word on steel naming, at least as I know it from the knife industry. When one refers to the "10xx" series of steel, that basically means it's "carbon steel" or that it has no intended alloys. That's why it's preceded by the "10." The XX part is going to be the percentage of carbon... afterall... iron + carbon = steel. So when you see 1018 steel, which is "mild" or "low carbon" it means there is .18% C. Other common steels are 1040,1045,1050,1060 and 1075 but these are medium carbon steels. High carbon steels are basically 1080 and up.

All of the steels in the 10xx series are referred to as "carbon steels" or "simple carbon steels." Many small coil and leaf springs are made from these.

The 51xx series is similar, without getting into detail, the "51" means it has a little chromium in it. Therefore, 5160 has .6% carbon, making it a medium carbon steel, but NOT a simple steel technically. This is what automobile springs are made from.

[krept]

explain the balance stuff, if you would. don't really care for extensive crazy research, just yer stance.

anyhoo, as i recall, stainless didn't really like taking a great edge and it wasn't that effective overall for blades one way or the other. carbon steel remains the champ in that respect, unless i really, really got outshined by technology.

don't often recall a great edge from a stainless blade in my own lifetime. they're <censored> on wheels.

stainless, as i recall, is hard - either you stamp it cheap and thin or you break out machining and suffer a profit cut. most tend to be pretty inferior in feel, nevermind the look.

just my thoughts, don't shoot me, anyone.

Crucible steel is one of the companies at the forefront of specialized stainless steel production. They have taken the aforementioned 154CM and used applied their "crucible particulate metallurgy" process to make it, ensuring very fine grain size which directly translated to a fine edge. Another great stainless steel for blades is S30V, great stuff... but they are both very expensive.

Simple carbon steel is great because it will hold a fine edge, while still being relatively easy to maintain (resharpen). Alloys in stainless, especially those mentioned above, make it a relative PITA to maintain.

If you are interested in what a GOOD simple carbon blade can do, check out the journeyman test for the ABS, below:
http://www.americanbladesmith.com/ABS_JSTest.htm

I've never heard of a stainless blade that can do that.

Just so you know I'm not biased... Strider knives are my favorite and the reason I got into knifemaking. They almost exclusively use S30V stainless for their blades... the main reason being is they definitely want that extra corrosion resistance.

[krept]

explain the balance stuff, if you would. don't really care for extensive crazy research, just yer stance.

The balance in steel wavers mainly between toughness and hardness. A very extreme example would be comparing a crowbar to a piece of glass.

A crowbar is TOUGH but won't hold an edge. It can pry very well and if push comes to shove, it'll bend or dent. Chances are it will NOT break.

Glass is HARD. Often times people hit the tip of their knife on glass and it deforms or breaks. Why? Glass is a lot harder... but it's not tough. Clearly it gets sharp, but often too sharp for our purposes.

An example related to knives would be, well a scalpal versus a machete. You can make the steel hard like glass and it would make a good scalpel... slices very well and doesn't bend. OTOH, you can make steel more like a crowbar... don't need that good an edge for a machete, but you want it tough becuse you'll be hitting hard wood and rocks that could shatter a blade that isn't very tough.

Wanted to add the thing about heat treatment... all you need to do with simple steel is get it to nonmagnetic (where a magnet won't stick) and dunk it in oil to cool it down. Water is better to obtain maximum hardness, but it frequently breaks steel. After that, pop it in an oven set to around 400 (depending on the steel) and cook for a while and voila... you've got a tempered piece of steel. I use a propane forge to do my work... on thin pieces like picks, i'd venture to say that one of those torch lighters or a BBQ grill might do the trick. Basically, nonmagnetic is when it gets to a dull red.

sorry if i rambled!

thanks again for the input. hope I can get good at picking and contribute in that respect.

cheers

[pretender]

thanks for the info. probably help a good bit of people besides me.

will agree on stainless not being *that* good for picks. think people get a wee bit too obsessed over such. it's pretty tough stuff to shape and lacks some of the resiliency a good carbon steel will give you.

my rule of thumb is that the picks get made out of carbon steel, and the tension wrenches are always stainless.

destructive testing on my heat-treated stuff has had a fairly positive result; the amount of deformation necessary to screw 'em all up is absurd.

then again, who knows - perhaps people recreationally chop down trees and unbolt alternators with their picks...

[vector40]

Rust does happen on picks, to be fair.

I miss my Sebenza...

[Shrub]

Hmmm far too much reading to keep my interest on a subject i know a lot about but i did notice in your first reply as i skipped over it was your use of numbers, in the UK we still regulary use EN numbers which were from the war, during the war all sorts of material were being collected with little thought to strength or other properties, you may have a tank made from nothing more than tin and then high grade steel for the next so they standardised it all and gave them numbers prefixed with EN (Emergency Number) the higher the number the better the material, EN3 is mild steel, EN24 is a very good quality steel that can be hardened to a good hardness then theres extra letters on the end of that which determine the ardness of the material, EN24T is a very good steel that will be hard from the box but can be hardened a lot more, its free cutting with the right tooling and gives a nice finish when worked but still rusts.

Off topic but thought i would mention it.