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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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What I used...
I am sure you could substitute in your own preferences where appropriate. My goal was to use as much of what I had on hand as possible. If you don't have the same items on hand, then I would suggest improvising. Although everything can of course be purchased online, or at your local hardware & lumber store. My cost was about $20 - $30. If you had to purchase everything, it would probably cost around $50 - $70.
FOR THE MAGNETIC COMBINATION LOCK MECHANISM & KEY
0.75" Thick HDPE Plastic*
2" dia. x 0.625" HDPE Plastic (Only required if you don't have the ability to turn a rectangular piece of HDPE on a lathe to a 2" cylinder. Make sure the surface finish on the ends is a high quality, not rough cut. These are actual dimensions, not nominal.)
17x 6mm dia. x 1.5mm Neodymium Magnets Grade N42*
4x 0.375" dia. x 0.75" Neodymium Magnets Grade N50
3x 1.25" Smooth Shank, Flat Head 3d*
1x 2.5" Long Furniture Finish Nail, Smooth Shank, Brad Head 8d*
0.093" Thick Plexiglass
2x 8-32 Aluminum Rivet Nuts*
1x 6-32 Aluminum Rivet Nut*
2x 8-32 Pan-head Machine Bolt & Nut (ferrous)*
FOR THE PICTURE FRAME & SAFE DOOR
0.75" x 1.25" x 58" of Oak (Actual Dimensions)*
0.75" Birch Plywood (Actual Dimensions)*
8x 1.25" Furniture Finish Nails*
Wood Glue*
0.093" Thick Plexiglass
2.5"Aluminum Tube (Inner diameter should slide freely over 8D Brad Head Smooth Shank Finish Nail)*
Wood Stain & Clear Coat
FOR THE WALL SAFE
0.5" x 3.5" x 78" MDF*
Wood Glue*
0.75" Drywall Screws*
0.25" x 14.5" x 24" MDF*
1.5" long Wood Screw*
2x Concealed Cabinet Hinges*
A Few Inches of Metal Plumbers Tape or Hanger Straps
*These Items I had lying around. I prototype and design products regularly for a living. Don't feel bad if you don't have them because the internet or a local supplier will. :)
IMPORTANT TOOLS I USED:
Machining Mill
Metal Lathe - Optional if you buy HDPE 2" Rod for the tumbler instead of rectangular HDPE. I had lots of rectangular HDPE.
Drill Press
Cordless Drill
2 1/8" Forschner Bit
Patience
A Note About Necessary Tools...
I know a mill and lathe are not the most common shop tools. I have them, so I use them. They do make life much easier to prototype precision parts.
But I wouldn't let not having those tools stop me from trying to build a magnetic combination lock. The main material I used for the lock was HDPE plastic. It can be worked with most wood working tools. Of course not as precisely; however, modification of my design for greater tolerances should allow you to get by with a basic wood working setup e.g. drill press, bench jig saw, dremel, and exacto knife to clean up edges. The tolerances really could be much looser. Like I said, I have the tools, so I use opportunities like this to practice precision milling. There is something very satisfying about drafting a part and then creating a real world duplicate within a few thousandths of an inch. But please don't let the precision tools scare you away from trying a similar design if not the exact same. It really should be quite doable with an extra helping of patience.
You can do it...
If you think things through carefully and use some creative techniques, you can probably do this all out of wood--except for the locking pins and magnets of course. My first non-magnetic combination lock was out wood. However, you may need to use more powerful magnets if you're not careful to keep minimal drag on all moving parts, especially any of the moving parts that are moved by the force of the magnets.
Although I should warn that you should be cautious about using overly powerful magnets they can be dangerous.
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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.
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.
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.
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.
Thanks for the compliments!
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.
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.
Picky I know, but so easy to avoid...
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.
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
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.
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.
Good job man!
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.
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!
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.
Tnx!