Appropriate grades of steel for fine tools

[rohare]

I searched around a bit first, but didn't find anything that addressed this particular point.

I'm making (or trying to make...) a decoder for dial padlocks that requires passing through the hole used by the shackle. Because of the wide variety of tolerances of these holes (even for the same brand and model) I've got to keep the tool extrememly thin. I'm going to experiment a bit with stiff wires of varying diameters but am concerned that the very thin tools will bend wth the wheels rather than transmitting the position of the wheels. And of course the useful life of a tool is pretty short if it's so delicate. So what I'm wondering is what specific grade of steel (or some other metal?) would be best for such a tool? I'm looking for stiffness and resistance to change of shape, even when very thin or of tiny diameter. From what I've read, spring steel is a good place to start looking, but even in that subcatagory of steel there are many differing grades. Thanks much for any help!

[GWiens2001]

Some hardware stores have a variety of sizes of music wire, and as long as you are not overly rough, it seems to work for some fine work I do. You might consider that. If you are in the United States, Ace Hardware carries it. They also carry a wide assortment of tubing for making tools and decoders. True Value hardware stores also are a nice source. Both are online as well.

Good luck, and keep us posted!

Gordon

[YouLuckyFox]

I agree with Gordon on music wire, I use a place called "Metal Supermarket" they give me the material and diameter I need for a lot of my projects. I just checked their website, they help you select the grade of metal you'll be needing (good descriptions for some grades of metal: http://www.metalsupermarkets.com/catalog/ALLOY_STEEL/ROUND_BAR Notice in the link I give it even explains the distinction of cold-rolled steel. That is good, but if you really want to dial things down, this site should help you:http://www.onlinemetals.com/steelguide.cfm
I make a lot of my own tools, so PM if you need help with specifics. Passing through the hole used by the shackle? Is it decoding with the shackle closed? Have you decided on a minimum Outside Diameter on the instrument you will be designing, yet?

[rohare]

You Lucky Fox,

Yep, the idea is to decode with the shackle closed. I've made a cutaway of a master lock dial padlock for proof of concept. The idea is to slip past the shackle (the side that doesn't come clear of the body), rotate 90 degrees and touch the 3rd wheel. Spin the dial the dial to the right until you feel the gap. Spin dial to left... etc. etc. Wash, rinse, repeat.

By the way, if someone has already done this and sells a tool for it, I'm gonna feel really dumb...

As for diameter, I haven't experimented enough to decide for certain. I know for a fact that .028 inches (about .71mm) will fit past some shackles, but not all. It's also a fit so tight that it obscures the feel of moving parts inside. I've verified this using feeler gauges and .028 just happened to be the smallest one I had. The decision on the diameter will be a trade-off between being small enough to usefully bypass the shackles, and being strong and stiff enough to accurately transmit data back to the user without deforming. This is why I want to find the most appropriate possible alloy for the tool. I want that trade-off to be a beneficial as possible. I've got a few lengths of stainless steel wire on order measuring .25mm, .36mm, and .38mm so I can do some further testing.

From looking at those two sites you mention, I think tool steel is the way to go ultimately. But for a final prototype I'll probably take you and Gordon up on the suggestion of music wire. Now the trick is to find such material in the ridiculous diameters I'm looking for.

[YouLuckyFox]

From looking at those two sites you mention, I think tool steel is the way to go ultimately. But for a final prototype I'll probably take you and Gordon up on the suggestion of music wire. Now the trick is to find such material in the ridiculous diameters I'm looking for.

You got that right, those type of dimensions are tiny! I would be very interested to see how things come along, please keep this forum topic updated! I have heard of several semi-destructive methods at accessing the gates, but nothing like using a probe to decode through the shackle housing! Tool steel is definitely a good option, but it is tough to machine! My paltry two cents would be to try getting some hypodermic needles of appropriate length (here me out, I have an idea ). They are made of cold-drawn (well, hot-drawn and then cold-drawn) 304 stainless steel which is not the toughest, but does have a good ductility which will be VERY important with such tight dimensions. Since the needle is constructed of a hollow tube, you can put a wire down it that has a little bit of memory in it (being bent to a certain curving angle and heated to ensure the angle before actually entering the tube), that is to say when it comes out the other end of the tube, it will curve out and into the gate of the third wheel. The advantage of this is that it preserves the feedback that would be needed to transmit data, but not at expense of strength. Your left hand could receive the transmitted data through the wire while your right hand held the tube steady. This is totally a long shot, but this is a readily available resource, they make syringes with Outer Diameters of the tolerances you need with varying lengths (a 22 gauge needle = .028 inches) and you'll have an easier time finding wire that will fit down the tube (as it is often used in the manufacturing process of the needles themselves) than finding a stock material of tool steel of the dimensions you're hoping for, but please contact any metal suppliers to find what they can do for you. And again, please keep this topic updated!
Best of luck!
YouLuckyFox
http://shopmedvet.com
http://www.sigmaaldrich.com/chemistry/stockroom-reagents/learning-center/technical-library/needle-gauge-chart.html

[GWiens2001]

I have some music wire that is .018" in diameter, from Ace Hardware.

Gordon

P.S. I have no affiliation with Ace Hardware. I just like the selection of tubing and solid metal for various materials.

[rohare]

Gordon,
Yep, ACE Hardware looks like the right place to go. If the stuff I have on order doesn't do the trick I will be making an appearance.

You Lucky Fox,
That syringe idea is awesome. I'm going to try my original idea first but I'm keeping that one in reserve. It actually sounds like a better idea overall.

Pictures will be forthcoming in a few days or a week.

[YouLuckyFox]

@ pictures: Please do, this is most interesting as when you get to the smaller dimensions, you really get to learn how differently some metals react than others. It can really come down to what specific metal you are using that will make your idea work; then again, might not.

[Dogrocket]

Another metal to consider if you use an exterior tube as a guide is Nitinol (Nickel Titanium alloy, also known as "shape metal") - very springy, returns to form, and has some interesting properties when heated.

[YouLuckyFox]

Great idea! This is like the Open Source Lockpick forum here.

[rohare]

Okay, I got in the assortment of wire gauges that I ordered and set to work on a cutaway dial-padlock I chopped up. The diameters I have to work with are:
0.015 in / 0.38 mm
0.014 in / 0.36 mm
0.010 in / 0.25 mm

They are all 304 stainless steel.

The .38 and .36 mm wires were too large. Just plain not enought clearance to get them into the body of the lock. The .25 mm wire just managed to slide past the shackle. Unfortunately, it wedges in with very little clearance and all feeling of what is going on inside the lock is lost. Furthermore, the wire is so thin that it wouldn't matter anyways. I tried simply ignoring the shackle and poking the wire directly at the wheels in my cutaway lock and spun them around. The wire bends and deforms so readily that I can barely detect the change in the wheel state through my fingers despite the fact that I'm looking at the wheels when I do this. Having a clearer passage past the shackle by using a syringe body would not solve this problem. Futher, any syringe with an outer diameter small enough to get past the shackle would necessarily have a smaller inner diameter requiring the use of a wire even narrower than the one I'm currently failing with.

I don't see that any grade of steel, however strong, would be sufficiently resistant to change at these diameters to actually work.

Of course, destructive means such as drilling into the back would still work, but that sort of defeats the purpose of the tool.

I guess my plans for world domination have been mugged by physics.

Unless one of you has some other genius suggestion that I'm not thinking of...

[YouLuckyFox]

Well, darn it. The syringe idea was a total shot in the dark, but wouldn't it look cool in a movie? I'll keep an eye out for your future posts, best of luck!