Instructables

Magnetic Combination Lock Picture Safe

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Why I would love to win a zing laser cutter...

Since I was little, I have been taking things apart; for years, I have been looking through and learning from Instructables. I love inventing, prototyping, designing. I love it so much I started a very small product design business with my wife from my home, where we design, cottage manufacture, and sell my own original products. As with most dreams lots of work is involved. Any help I can get that lets me focus more time on designing innovative products and less time on the day to day mechanics of putting those designs into action will allow me to reach my dreams.

A laser cutter would speed up my prototyping phase of product design. With more efficient prototyping, I can increase my output and troubleshoot faster. A laser cutter means more opportunity and faster innovation. I can certainly get my business going on my own, but it won't be as fast or as fun as if I won a zing laser cutter!


What I did to show my skills...

In this Instructable, I will show you how I created a great magnetic combination lock that be can be installed in an application, where you would like to leave no evidence of a keyhole or combination lock with the same security of both.

Inspiration came from a book my wife bought me on vacation from a thrift store: The Boy Mechanic: Volume 1 by Popular Mechanics Co. A very fascinating book detailing projects that popular mechanics published around the turn of the 20th century for boys to build. One project shows how to build a wooden combination lock. That intrigued me, so I built a simple version out of scrap wood. That got me thinking about locks. What I thought would be really great would be a magnetic version of the combination lock. So you could pull the key off, and no one would know it was even a combination lock. So after lots of tinkering, drafting, and failing I departed a long ways from the wooden combination lock design they had and came up with my original Magnetic Combination Lock. I am sure somebody may have done something similar somewhere, but I am unaware of it.

Before we get into the details, please check out the video down below so you can see the finished product and how it works. I would like to point out that the goal of my build was not to create an indestructible safe, but rather to prove my concept of a magnetic combination lock that was functional enough to keep honest people honest. However, the design can easily be implemented with much sturdier materials with little modification to make a safe that would keep dishonest people honest.

--Please read the safety disclaimer at the bottom before attempting to build.--




SAFETY DISCLAIMER: (Not many people like this part, but when you use big tools you take big risks when handled poorly)

If you attempt to reproduce this instructable, you will most likely be using sharp, pointy, dangerous, fast spinning, grown-up-person tools that can cause serious harm or death to yourself and others, especially if not trained properly on how to use them. You should have read all the safety warnings for your tools and understand how to use them. You should also use your tools as intended by the manufacturer with the the proper safety equipment.

Also, you may purchase powerful magnets that can cause serious injury to yourself or others if handled inappropriately (E.G. inadvertently or intentionally allowing them come together too quickly which can cause the magnets to violently explode and send little tiny sharp metal shrapnel bits into your eyes.) You should read all the safety warnings and understand proper magnet handling protocol to reduce the risk of injury to yourself or others. Please use appropriate safety equipment (e.g. protective eye ware, etc...)

I am not responsible legally or otherwise for any harm, injury, damage to property physically, financially, or any other unfortunate thing you may do. If you choose to build from this instructable. PROCEED AT YOUR OWN RISK!

 
 
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claudg19502 years ago
Great idea and great work!!
To further simplify the design: perhaps even simpler than a sliding lock could be a pivoting lock. The piece would only need a bolt as axis.
A source for free neodynium magnets: an old computer hard disk.
pastprimitive (author)  claudg19502 years ago
Thanks! I am curious as to what you imagine the pivoting lock looks like? I'm not quite able to picture what it would look like.

I am currently working on a simplified version that can be easily made with really basic tools. I will be posting another instructable on it. And your idea sounds like an intriguing path to follow.
My explanation wasn't clear. Sorry.
I am attaching a sketch which will show you that my idea, after all, was offensively simple. Inside the box, a magnet is permanently attached to the pivoting bar. Then, from the outside, you glide your hand held magnet in a curve (see arrow) which will move the bar away from the rest, thus unlocking the box.
I'm sure you could improve a lot on that (for instance, adding a second pivoting bar which would prevent the main one from pivoting unless you displace that one first...)
My point is that there should be a lot less friction with a pivoting than with a sliding bar. All the best.
Pivoting magnetic lock.JPG
pastprimitive (author)  claudg19502 years ago
I see. I actually had something completely different in my head when you said pivoting arm. This makes much more sense. Has the advantage of being able to place the magnets so that you can get a force multiplier that would make it easier for a less powerful magnet to move the bar.

I am working on the simplified version of the lock, and I just might incorporate this idea of a pivoting locking bar in the design. Thanks for expanding my through horizons. Very clear picture.
I'm glad I saw these comments, thanks for the simplification idea. Just posting constructive comments like these helps people think outside the current idea to keep it evolving. I love it!

Is there any new update or post with a pivoting bar?
I will definitely have to try this.
noahh2 years ago
Very cool project. It would be cool if someone with a 3D printer posted files on Thingiverse allowing others to print the parts rather than having to machine them, which would make it easier for people to make something cool like this.
pastprimitive (author)  noahh2 years ago
I would love to make it easier for people to make. I have all the parts already drafted in a cad program. If you told me what format they need to be in I would gladly post them? Or is it a proprietary format unique to 3d printers?

Thanks for the compliments!
I don't know a whole lot about 3D printing, but a bit of research shows that STL formatting seems to be common. Thingiverse has a list of file types that work.
pastprimitive (author)  noahh2 years ago
Well I will take a look at it and get those files posted.
do u know wear u can find 3d 1.25 smooth shank flathead nail?
pastprimitive (author)  StReEtCrUsH352 years ago
It should be a standard nail size carried by most hardware stores. I got mine from Home Depot. Here's a link.

http://www.homedepot.com/Tools-Hardware-Hardware-Fasteners-Fasteners-Nails-Box-Nails/h_d1/N-5yc1vZbua5/R-202308634/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

The one confusing thin I noticed is they don't carry it online under it's penny designation which is "3d" they carry it as a 14 gauge nail.

Hope this helps.
wat are the dimensions for this
awesome thanks
like wats the length for each line and stuff like that cuz im tryin to replicate it
pastprimitive (author)  StReEtCrUsH352 years ago
Originally I machined my key by using the technical drawing of the tumbler from step two, and placing the four holes so they lined up with the corresponding holes on the tumbler technical drawing.

However, I went ahead and updated step 8 of the instructable with a technical drawing I drew up of the key for you, and other future readers. I wanted to make it a little simpler to machine; with less work on the readers part to figure out the dims.
Thetis2 years ago
It might be the picture, but the holes in the plexiglas look pretty rough with darkened edges. Plexiglas (Perspex to us Brits) can machine really nicely to a great finish, but only at low speed with good sharp tools and a gentle approach. Higher speeds heat it up very quickly and it melts and burns, which is what looks like happened here.

Picky I know, but so easy to avoid...
pastprimitive (author)  Thetis2 years ago
Picky is fine, I am glad you pointed it out. Especially since you had advice on how to do it better.

While the holes don't have dark edges in real life (just in the picture) they definitely are rough. I am a self-taught machinist. Everything I know I learned online, or taught myself through trial and error. There are many techniques and materials I am just not well educated in yet. Perspex (Plexiglass) is one of those.

I ran it at a higher speed because in the past I have cracked workpieces When running at lower speeds. But I am assuming that is my own bad machining/clamping technique combined with my more likely than not dull cutters.

I am going to go try machining some more plexiglass and follow your instructions to see if I can get cleaner surface finish. Do you have an rpm suggestion to try cutting at?

Thanks.
Now you are asking! I have to confess that I'm not terribly scientific about speeds, I tend to just go with what feels right. Which is no doubt why I've melted so much perspex!

The rpm to use is, of course, directly related to the nature of the job you are undertaking and the main thing to bear in mind is keeping the temperature down. Recommended speeds are usually given as a linear speed (eg, metres per minute) which you then have to translate to the appropriate rpm and feed rate. As an example, I'd be choosing a speed at something below 200rpm to drill a hole, and probably well below that to drill a deep hole (because the heat builds up down there), with lots of pecking to let things cool down.

However, blunt or inappropriate tools, or trying to feed too fast, or too slowly will also increase heat production so it is difficult to be precise. Nothing improves your work so much as a good, sharp, appropriate tool. If you are having problems with cracking have a go at altering the rake on the drill - it takes a few seconds with a stone slip, or you can buy drills optimised for drilling soft materials.

This document has lots of useful information: http://www.theplasticshop.co.uk/plastic_technical_data_sheets/working_with_perspex_manual.pdf
pastprimitive (author)  Thetis2 years ago
Thanks for all this good information. Especially with the links. Won't complain about somebody willing to help me get better. I browsed the pdf you sent the link to and what an awesome document that was. Those are the kind of informational packets a self-taught machinist lives to find.

I remember reading about feed speeds in milling. But I have never paid much attention to that because since my mill is a manual turned mill; a Sieg SX2 to be precise. In the past It's always seemed quite obvious what the feed speed should be because you got lot's of feed back through the hand wheel on how well it was cutting. If you fed it too quickly and chatter would increase. Of course plastic is not as obvious because it is so soft.

Thanks again.
bogie46462 years ago
This is an awesome instructable, great work. I've been currently trying to think of something to build based on a combination of instructables that I've seen and now I've got another aspect that I want to put into it.

Whenever I figure out my final design and build it, everyone that has given me inspiration will definitely be credited. The unique ideas in instructables like these are what make this site so awesome.
pastprimitive (author)  bogie46462 years ago
Thanks. I am glad I could be of some assistance.
jab05922 years ago
This is really awesome! I am thinking about making one and to hide the key, I was going to imbed it into an ornament, kept local to the safe. This allows boths parts of the device to remain secret, covert and more fun :D
Good job man!
pastprimitive (author)  jab05922 years ago
Thanks. I love your idea of embedding it into an ornament.
whiteoakart2 years ago
This is really impressive. As a product designer and benchtop engineer, I love this sort of thing. I don't imagine a need to build anything this complex myself, but I could see using the ideas to make a hidden slider lock as some of the other comments have mentioned.
pastprimitive (author)  whiteoakart2 years ago
Thanks for a generous compliment. Sounds like another vote for getting the simplified version posted.
(removed by author or community request)
He mentions that in the 'ible. To have a more secure device, one would make the entire thing out of "sturdier materials" as noted.
Stevos2 years ago
awesome!
pastprimitive (author)  Stevos2 years ago
Thanks!
LifeWarrior2 years ago
Very cool idea! Wouldn't be easy for those without the tools but still cool! I love the type of extreme ibles, because they are inspiring. My first thought was how could the average guy with a few hand tools do the same thing or something similar, so for a part 2 a simple magnetic slide lock (thinking of a flat barrel lock of sorts), Granted it would be as secure as a keyed combo lock but then again it's already hidden by the picture frame, but still very bada**. great job!
pastprimitive (author)  LifeWarrior2 years ago
I agree that it would be awesome to make another version of the magnetic lock that would be a simple magnetic slide lock that did not require a tumbler. It would be awesomely easy for someone to make with simple hand tools. Although the security would not be quite as good as the combination lock, but still provide the benefit of a hidden locking mechanism that required a specific key.

In fact while I was thinking through the different designs for the magnetic lock a slide lock was high on my list of candidates to prototype. But I decided to go for the combination lock design; because it had the alluring feature of still being very difficult to unlock even if someone found the key. I geeked out over the coolness of redundant security features. But I think I need to post another instructable for the slide lock version as well.
The combo lock is definitely a contender for the contest, Some of my favorites that I'll actually try to recreate though are the ones that are useful this one fit's the bill, however I probably won't get lock elaborate like the combo, that's one reason I suggested a follow up with a basic locking mech. like a slide. My thought is for my situation if anyone even finds it or a thief realizes it's there, probably nothing I can build by hand to keep them out of it. However for keeping teens and curious family members out of it the combo lock would be slick to have. I've even considered an infrared led in the frame to trip a servo to unlock but again way too much work for a hiding space, however I've considered it for a small wall safe I have. But abandoned it because of a hotel door lock that uses a magnetic strip card (acquired from a junk pile) that I'm trying to figure out.

Yes I'd love to see the slide lock though, I was already looking around my shop for materials after seeing this. Very cool take on the wall hiders, thanks!
pastprimitive (author)  LifeWarrior2 years ago
Thanks for your confidence. I hope it's a contender as well. Teens and curious family members is exactly what I thought this would excel at. A determined enough individual can break through just about anything. But keeping honest people honest is usually a much easier process. Although I would like to make another safe that is built from steel for the body, and door. But I would use stainless steel for the door so it would not interfere with the magnetic lock. Since stainless would not interfere with the magnetic lock device like regular steel would.

I will follow up on your suggestion and put out an instructable on how to build a simpler version that doesn't require the use of precision tools. I think it's a great idea, and a natural progression of making it more accessible.
This is way cool. I would also like to see an instructable for the simpler version. I have an old lighter display I'm trying to find a way to lock. It already has a lock but no key and I don't want to be in position of having to pick it each time I need to get into it. I think the slide lock might just fill the bill.
pastprimitive (author)  paqrat2 years ago
Well, I'll do my best to get the simpler version done as soon as possible.
Good instructable but maintain good distance of your credit cards when handling Neodymium magnets!
pastprimitive (author)  Rudiger Schulz2 years ago
Thanks. Good point about keeping credit card away.
Tkdwn2 years ago
Love it!
Tnx!
mikeasaurus2 years ago
awesome idea and loads of detail, thanks!
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