I built this wooden combination lock model back in 2008,
but I never made a video of it's construction.
So, I thought I'd build it again to show the process.
And, I've got some of the key drawings printed out here,
and now I just need to cut them out.
The glue didn't stick that well, so I'm just gonna
use a couple of small nails through these holes,
to keep them aligned while I cut them out.
I need three of these and one of these
and these things are mostly just circles,
so I'll cut them out with a compass.
Every time I cut out a circle on the bandsaw,
I get comments about circle jigs.
Circle jigs just aren't worth the bother.
Now, these discs are supposed to fit
fairly loosely onto the dowel,
but it's really tight, so I have to sand down that dowel
a little bit to make it fit better.
The three rotors have these tabs,
which allow one rotor to engage the next rotor,
and that's how the rotor, all the way in the back, is turned.
So, next I need to cut a slot into each rotor
to accept those tabs.
Now, this thing should turn freely in here,
but it's awfully tight, so I should have sanded this dowel
down a little bit, but it's too late for that now.
so I'm just going to expand the holes a little bit
by sanding the inside of them.
The first rotor has got this piece here attached to it,
which couples to the knob.
And, that is a slightly thicker ring, like this.
When attaching the back to the lock,
I have to make sure that this dowel ends up
in the middle of this hole.
Now this thing only comes up just barely far enough
to clear the bar here,
so I need to put a stop on here for that position.
When I assembled this part in here,
this bracket, I put the dowel too far this way,
which means I don't have enough length sticking out here.
So, I am just going to do something very crude
which is to end-grain glue another piece of dowel on here.
And, the straight up end-grain against end-grain joint
actually is surprisingly strong,
so I think it will do for this application.
Depending on how things work out, in terms of
thicknesses of plywood, you may need an odd size washer.
This one is sanded down from a quarter inch.
Then we put the back rotor in, middle,
front, and then that fits in here.
And, that should come to about the front of the plywood.
And, then the knob goes on here.
Now, the knob somehow needs to be coupled with this rotor.
Now, there's nothing that keeps the know from pulling off,
so we need to put a screw in the front of this.
I also made a couple of thinner washers,
by sanding them to keep this part centered.
And, that goes in here.
And, then the knob goes on here.
And, the knob is horizontal when this part is vertical.
And, that would be a good position for the knob.
Then our lock is almost done, but it's missing
one important detail, and that's the slots in the rotors that
actually set the combination. I wanted to set the combination
to Pi, which would be 31:41:59,
but the dial only goes up to 39,
so instead I'm using the constant e,
which will be 27:18:28.
And now I just need to mark what position my rotors ended up in,
and that's where the notches need to go.
Now, I still need to install the bolt
and that's best done with the lock in open position.
Slides in the back, like that.
And, a screw to keep it from falling out again.
Now Ideally in a lock like this,
the rotors would have a little bit of friction, so that if you
dial a little bit too fast, the rotors won't over-shoot,
like they do on here, but that would be very difficult,
because if I make these so they rub on the dowel,
as soon as humidity changes, they either become loose,
or become jammed altogether.
So, the key on here is just to dial very slowly.
It's not really a practical lock it's mostly for demonstration.
If you'd like to build a combination lock
like this yourself,I have a set of plans for sale on my website,
but you do need a bandsaw. If you don't have one,
I'd be more than happy to sell you the plans for that, too.