1 Comment on Physical Keygen: Now for Disc Detainer Locks
The Physical Keygen post got reactions, but there was a common claim among many of them that it was just a gimmick because there are more practical ways of getting past basic Schlage and Kwikset pin tumbler locks. I agree with that, and I’ll also admit that a fair number of my projects are gimmicks, or as a stretch, art. Schuyler Towne of Open Locksport saw past the gimmick (or art) and into the possibility of printing keys for more interesting locks.
He stopped by recently with a collection of said locks, and over the period of a few hours we determined that keys for disc detainer locks were printable and created a nearly working ABUS Plus key. He left me a cutaway lock, and over the next week, I refined the model to the point of working straight off of the printer. Despite being a higher security lock than the SC1 or KW1 pin tumblers I was working with before, the key is much easier to print accurately. The OpenSCAD model is linked below, and like the last files, you simply edit the last line to match the code for your key.
The ABUS Plus and other disc detainer locks are much more common in Europe than the US, but we do have a pretty ubiquitous example around here. After the Bic Pen debacle in 2004, Kryptonite switched their bicycle U-locks from tubular to disc detainer. I designed a model off of the key from the Kryptonite Evolution I have,
but as of yet, I have not successfully opened the lock with it. The key is smaller and thinner than the ABUS Plus, causing it to flex too much to effectively turn the last few discs. I’ve posted the file anyway, in case someone has stronger plastic or an idea to strengthen the model.
Edit: The Kryptonite key works. I tightened my X and Y belts and printed it a bit slower. Apparently some of the blobbing on the corners before was catching on disks.
52 Comments on Physical Keygen: Duplicating House Keys on a 3D Printer
It occurred to me recently that I had printed almost nothing actually useful on my RepRap 3D printer, aside from parts to improve on or build more RepRaps. I am rectifying that with this project. The goal here is to generate working house keys by inputing the key code of the lock into a parametric OpenSCAD model. Instead of having to explain to my landlord how I ended up with a wedge of plastic jammed in my front door, I ordered a box of (well) used locks and latches from eBay to experiment on. Luckily, the lot includes both Kwikset KW1 and Schlage SC1 locks, which are the two most commonly found in the US. I created an SC1 model to start with,
but I’ll probably make a KW1 soon. I’ve uploaded the KW1 model now as well.
Designing the key model was actually pretty straightforward. I measured a key with a ruler and calipers and created an approximate model of it that is reasonably easy to print. I then got pin depth specifications and parametrically differenced them out of the model. To generate new keys, you can just edit the last line of the file and enter in the key code for your key. If the code isn’t written on the key, you can measure the height of each bit and compare to the numbers in the Root Depth column on the aforementioned pin depth site. Perhaps more nefariously, you could implement something like SNEAKEY to generate key codes without physically measuring the key.
You’ll of course need OpenSCAD to edit the .scad file and generate an STL to print out, unless your key just happens to be 33172 like the example STL posted below. If it is, you can unlock the doorknob currently sitting on my desk. As a small, precise object, this is a great test of how accurate your Skeinforge settings are. You may need to adjust some thicknesses or the built in pin depth fudge factor to get it working properly with your printer. The pictures above show the key being used on a disconnected lock cylinder, but I found it was also strong enough to turn a deadbolt. If your lock needs a lot of force to turn, you may need to cut a space into the key to use a torsion wrench with it.