This project creates an end product of similar design to my other lock instructable: www.instructables.com/id/Wooden-Bar-Combination-Lock/
however this project has:
->A much higher complexity level
->Requires more time
->Requires more esoteric building materials
->Much harder to circumvent/guess
->User changeable code
This instructable will take you through constructing a wooden dial combination lock. This particular lock will in fact be used to secure a minibar fridge (replacing the one I have already built) due to some issues with the misappropriation of foodstuffs at my workplace.
This is a moderately complex project that can be completed inside of 9 hours if you move quickly and don't make any major mistakes. Workpeice precision is a must in this project, and you should assure that you have access to some moderately precise tooling.
During the course of this project you will also be creating the dial in virtual format using openoffice (marking it by hand would be a disaster) and then printing it to transfer it permanently to the dials on the finished product.
Openoffice with fontwork installed
3/4 inch pine
1/2" internal diameter compression type spring
Nail gun nails
Step 1: Initial prep
Take your 3/4" pine, and plane it even
Cut the following pieces:
3 9x12" boards
2 3x12" boards
1 3x32" board
9 3,1/2" disks
4 2,1/2" dowel
2 5" dowel
Step 2: Prepare the slide mechanisim
Place the two 3x12" boards on the sides of one of the 1x12" boards, this should allow just enough space for the 3x32 board to slide up and down inside the slot created.
Step 3: Prepare and drill the lock plate
There will be a single spring loaded lock plate which moves forward and backwards inside the unit. Start by taking the second 9x12" board and placing it on top of your existing setup, draw a line down the middle of the board (this line should overlap the slide underneath)- drill holes at regular lengths (the lengths do not matter, I used 2,1/2"). Drill through into the slide.
Use a 1/2" drill bit on the lock plate to make larger holes.
Screw in some 1" screws into the slide.
When complete it should look like the last picture here; with screws poking up into the holes, holding the slide firmly in place with minimal play.
Step 4: Preapre the dial plate
Take the last 9x12" plate, and draw lines at 3" down and 2" in.
Drill these out on the drill press to 1/2", then wiggel them around in the drill press to make them SLIGHTLY larger then 1/2"- your 1/2" dowel should be able to freely rotate in these holes, but otherwise be held firmly in place.
Step 5: Cut 9 disks
Cut 9 3,1/2" disks (Easier said then done, which is why I'm making it its own step)- you cut 9, because one of them will look like garbage and then need to be tossed away. If you have a lot of time, it may be preferable to lathe a long bar, and then cut that in a fine table saw blade.
Step 6: Find the centre of one disk
Take one of your disks and determine its center (I used this method : www.mathopenref.com/constcirclecenter2.html), the black marker was my first attempt to use the method, and the pencil line the much more successful second attempt.
Once you have found the centre point, transfer it to all other disks.
Then drill out each disk with the 1/2" drill bit on the drill press.
You should drill the hole with a small drill bit first so that the disk does not want to shift as you press the 1/2" into it, this will help keep the holes consistent and in the middle- absolutely precision is NOT required here, but your final product will look far more sloppy if it is not at least close.
Step 7: Add an offset hole to 4 disks
On 4 of the disks, add an offset hole, just somewhere off to the side- it should be consistent, so use the same transfer method you used to add the center hole. Expand this hole with the 1/2" drill bit like you did with the center hole.
Step 8: Glue the dowel into the 4 disks with offset holes
Glue the dowel into the 4 disks with offset holes, have the dowel be just in line with the bottom of the disk, wait until the glue is completely dry before continuing with these disks.
Step 9: Drill marker holes in the dial plate where the offset holes in the disks are
Push the rod conatining offset hole disks into the respective holes in the dial plate, and drill marker holes at a set point where the offset holes line up (since you already have lines on there a good rule of thumb would be 'on the line, twoards the outside'- this way if you forget which side is which or have an issue with how things will change when you flip it upside down everything will be perfectly mirrored.
Step 10: Place your marked disk plate onto the lock plate, and tansfer the holes, and make slide rods
Place your marked disk plate onto the lock plate, and transfer the holes. As long as you have everything lined up like this place two rod holes in the middle of the project using the drill press- these rods will be what the lock plate slides on when in operation. Finally create a recess for the spring in the middle of the lock plate, and create a spring pocket in the dial plate.
Step 11: Create the dial pattern
click on 'fontworks gallery' in the window that appears
Select the default display
Type in your number series (Tip- remember to include zero and an ' above each number; unlike me....)
Select Circle format
Use the yellow circle to make all numbers be around the outside edge.
Make fill colour black
Change shape and size so that it will fill your disks.
make 4 of them
Cut out each one
Attach with spray adhesive
Step 12: Manually add ticks with black sharpie
Step 13: Put it together
No really, it all just snaps together from here, put your spring in place, and just slide everything together. Then secure the top plate to the bottom plate by JUST the clearance of the screws in the lock plate to the lock bar between it and the lock plate (So that if you were able to lift the lock plate to be pressed right against the dial plate it would allow you to pull the lock bar down/out.
(Spring not installed in side view images so I could illustrate what I am talking about above)
Step 14: Attach a pull handle to the lock plate
If everything is working correctly at this point you can kind of sort of manually push the lock plate up against the spring when the correct code is dialed in and slide out the lock bar, but it takes a lot of effort, and it's kind of debatable where the positions are for 'correct code'
First thing, lets make it easier to move; attach two bars similar to what is holding the dial plate to the base plate to the lock plate (And only the lock plate) then connect these via another piece of the dowel, so that there is a sturdy handhold which will pull evenly directly against the spring.
Step 15: Add position indicators
There are so many numbers, and it is all so fine that you need a precise indicator to see where you are, do these up by taking some simple cubes- and nails that are far longer then they are, then fire your nail gun through them (making sure you are doing this over open space, with nothing fleshy underneath in case it blows clear through) and then fasten these to the face pointing to the ticks for there location.
Step 16: Drill angled holes into the dowel
Drill angled holes into the dowel at each dial, large enough so that you can push a finishing nail or pin into place. These will keep the number from being shifted when you don't want it to be shifted through casual friction with the wood.
Step 17: Mount and set combination
Mount your finished product, remove the fix pins, dial in the current working number, pull the lever engaging the action, and now rotate the dial to whatever numbers you want the new combination to be.
Since the screws in the lock plate are preventing the offset hole disks from rotating, and the pins preventing the numbered dials from rotating have been removed the numbered dials will rotate to whatever number you want to be the new code. Replace the pins when complete to assure that they do not rotate accidentally.
Also- if you are me you realize that adding a zero, and a zero tick at this point might be a good idea, so you add that with the sharpie again.
If you've made it this far you now have a rather complex, somewhat bulky, and functional lock that has roughly the resilience of a suitcase lock. It does however look quite impressive and can hopefully inspire people to not steal things from your fridge/other locked location. Changing the code will also build your upper body strength if you used a spring with as much resistance as I did.