Wooden Bar Combination Lock





Introduction: Wooden Bar Combination Lock

This instructable will take you through constructing a wooden bar combination lock.  This particular lock will in fact be used to secure a minibar fridge due to some issues with the misappropriation of foodstuffs at my workplace.  For a more complicate locking mechanism with more features check out (www.instructables.com/id/Wooden-Dial-Combination-lock-with-spring-release-/ ) also by me.

This is a fast, relatively simple project that can be completed inside of 3 hours if you move quickly and don't make any major mistakes.  Further you can plan around irregularities in your workpieces allowing for greater ability to use scraps.

Tools Required:
Circular Saw
Table saw
Band Saw

Materials required:
3/4 inch pine
1,1/2" screws
~3 hours
Felt pen
Grease pencil
Wood Glue

Step 1: Cut Peices

Take your 3/4" pine, and plane it relatively even.

2     9x12" boards
2     3x12" boards
1     tapered 2,1/2x32" board, tapering out to 3,1/2"
5     3x24" boards
16  3,1/8x3 boards
10  3x1" boards

Arrange your materials neatly, affix the 3x12" boards to the sides of one of the 9x12" boards creating a notch in the middle

Step 2: Check Your Taper

If you have set the taper correctly on the 32" long board, it should slide into the notch, but not slide THROUGH the notch, it should snugly stop advancing if you attempt to slide it along.  This is important if you want the lock to only release in one direction.

Step 3: Dry Fit, and Then Glue, Bars and Risers

Arrange the bars and risers (3x24" pieces and 3,1/8x3" pieces)- The 3,1/8 pieces are ever so slightly higher then the 3" pieces allowing for them to slide with ease.  Then carefully fasten them in place, I used wood glue, be sure not to let them slide about, or let the glue drip.  Wait until dry.

Step 4: Mark Gaps With Grease Pencil

Mark the gaps with the grease pencil, the individual 'tumbler' stops will be placed here to prevent the rod from sliding out.

Step 5: Add Stoppers

In this case I just loose fit some 1,1/2" screws, drivigin them in just enough so that they did not protrude out the other side of the wood.  Always pilot your screw holes!

Step 6: Cut Notches in 24" Boards

Not pictured; but each 24" board needs a notch cut into it large enough to admit the screw- preferable with some play, but if you want to make the lock far more infuriating, or simply provide more, more accurate, numbers you can make it so small so that the screw barely has any side to side clearance.  Assure you have adequate top to bottom clearance.

Step 7: Add Guides, Lines, and Numbers

Screw on the other 9"x12" board on top of the previous one, sealing the boards inside

Use the 10 1" pieces of wood to cap each bar, so that they cannot slide out.

Use the remaining pieces of wood to construct a guide for the tapered piece of wood to prevent it from skittering about, note that one board will have to be cut as shown so admit the screws.

CAREUFLLY look inside the mechanism so that you can see right through it (IE- all notches are lined up), and draw a line on the side you are keeping your marks on with your red grease pencil.  Then slide all off the bars out and put your numbers on.  You can see that the combination for this lock is 3,8,3,8,3 (Hopefully none of the food thieves I am trying to keep out of the fridge read instructables!)

Slide the lock bar into place multiple times (screws facing down) in order to make sure that you have not shifted anything while applying your numbers and lines- if you find that one has shifted and is marked incorrectly sand and then reapply.

Step 8: Zero, Test, and Then Mount

Zero the bars by pushing them all to one side.

Then put the code in and try sliding it out again, do this 2 or three times, just to make sure that there is not a burr in there or something similar that will prevent use.

Then mount it wherever you need your stylish, functional, wooden lock.

Thanks for reading this instructable, hope that this gets the creative juices flowing.



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    It's an interesting idea, but given the fact that I can see the cut-outs in the bars that allow the bolt to move, I am skeptical about just how well it would work to keep out a reasonably intelligent human being...

    5 replies

    They are pretty exact, so just 'guesstimating' it would likely fail- however using a ruler or string, or other metric, would defiantly allow you to bypass it. See my upgraded version where I address this problem:


    Even that would be pretty easy to beat, taking less than thirty seconds to open. Just tilt one corner towards the dial plate, turn that dial until it jumps, repeat until it's open.

    Just to be sure that I'm not talking out of my ass I did in fact attempt this before my response.

    What you are describing does not work for several reasons:
    ->There are rods which guide the lock plate and only allow it to move (relatively) uniformly (you can kind of tilt top and bottom or side to side, but it's not actually enough to engage a single dial- it kind of works for two dials at once but that still leaves you with 26^2 combinations you need to work through)
    ->The spring tension prevents the type of fine feel that would be required to know that it has 'jumped' into position.
    -> Finally the pull tension due to the spring is ~15lbs, easy enough to pull if your just know the code, but becoming quite the weight if your trying to hold the spring in one hand and twist dials randomly with the other.
    -> (This one is a negative feature- but prevents guessing the code via your method) the front dials are only tension/pin locked, so if you are trying to twist them against resistance (say because your pulling the pins against them from behind) the back dial will lock in place, and you'll slip the pin in the front, changing the code rather then rotating the dial (I've had to dismantle it a few times due to people doing that because there was then no way to know what the code was)

    Ah, though it doesn't need much of a fine feel, unless it's MUCH easier to change the combination accidentally than I think it is.

    More an issue of 'it is very difficult to exactly hold a ~15lb weight with one hand while twisting a dial with the other' If you pull too tight the screw heads will dig in to the dials and hold them fast, too loose and you'll not feel anything when you pass the hole. Further the pull weight of the spring seems to be less then the weight required to get the screw to dig in- so you won't even know you have enough pressure, unless you have too much.

    This is of course my feeling for it, someone who cracks dial based safes for fun would likely not have much issue; but that's also not the sort of person I'm trying to keep out of the fridge.

    I love the implementation of this lock, how's it going for you?

    Also, a video of this in action would be great... ;D

    7 replies

    There is now a video- unfortunately it's in my phone's native .3gp format, so it does not seem to display natively in browser, and I can't get to reformatting it right this second.

    There is a free video converter... http://www.oxelon.com/media_converter.html that will allow you to convert to just about any format you may need.

    The existing format was viewable on most computers; it was just not embedded into the page in its own little iframe, this has now been corrected, enjoy the video.

    The video now attached should play if you click on it and just say 'open with default media application' it just does not happily form itself into a 'play inside browser' box. I am unlikely to be able to play with re-encoding a video until the weekend.

    YouTube accepts native 3gp files, and will do converting automatically for you, allowing you to download files once complete... Or just upload to YouTube and link there.

    I thought that might be the best way to acomplish this; thanks for the heads up. I guess I can't put off making a youtube account any longer then- expect to see these video's converted sometime this weekend

    Is the fridge mounted to the wall or desk? if not I would think it would be all too easy to simple slide the fridge over a few inches past the lock open her up and then slide her back and plead ignorance...

    3 replies

    Like most forms of lock security the purpose of this system is not to make the fridge impenetrable, but to simply make the attack vector take longer, and take more effort then simply opening the door and taking 8 juice boxes.

    Between the time delay, the noise, and the effort the new system seems to let me at least get a view of who's going into the fridge and make sure they don't take things that they should not.

    This is just me thinking out loud, but couldn't you just look under or down the back of the lock and see when the holes lined up and then make it work from there? Also, if you can see the notch from outside the lock, what keeps you from just guesstimating it and lining up the holes? I could crack this lock in like 12 seconds.

    1- Why not look down the back: You can't, well that's not completely true- you can see the first slider from the top, and the first slider from the bottom, but then the screws obscure seeing any further down.

    2- Guesstimating the holes: It is actually pretty precise, you'd be unlikely to guestimate unless you happen to have the level of spacial acuity to be able to judge things within ~1cm blind- people who are that switched on generally have better things to do with there time then steal from the fridge. See the video for how close you can be without it clicking through

    That said- non-guesstimating (like say, with a ruler, or any accurate measuring metric) would allow you to get the code quite easily- but I think that 12 seconds might be a little generous for how quickly someone is going to be able to measure and line up 5 separate sliders; of course, once you know the code, it's kind of set to there- see my other reference instructable for the upgraded version that has a variable code.

    So, once a few people knew the combination EVERYONE knew the combination, defeating at least part of the purpose of this device- so I decided to build a far more complicated lock that has a changeable combination; See the instructable here:

    (This link has also been added to the front page of my instructable in case eventually these comments bury the link).

    Also I was considering, and while a somewhat esoteric stretch- I believe that this project qualifies as making a password real, and thus qualifies to enter the make it real contest (Ignoring the fact that passwords were first used to make a digital lock). Hopefully the moderators agree with me.