Duplicating Disc Detainer Keys

by nrp, published

Duplicating Disc Detainer Keys by nrp Jun 20, 2011

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Writeup containing actual links at http://eclecti.cc/hardware/physical-keygen-now-for-disc-detainer-locks

The Physical Keygen post got some interesting 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 found 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.

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What printer resolution are you using? I used 0.20mm layers.

I've just tried on my UP! and though the key looks fine, it doesn't work. Seems really, really close, though. (And yes, I decoded the working key, so the code is correct)

nrp - in reply to -soapy-

Nothing special. 0.25mm layers, 0.5mm nozzle. Since you have the original key, compare the printed one to that. You may need to trim some corners/edges with a knife.

I'm not winning with this. I checked the code against the key card and the genuine key, and I tried a gentle bit of impressioning, but I can't figure it out.

I'm going to print a 3rd one, after I mod the code to print the backside as well, to give it a bit more strength and to allow for easier removal (it'll realign the discs more accurately when turned back)

I might also print one and run it through my Abus key machine to see where it takes material
away. That would give a really good clue as to the issue.

(As a note to others, unless you are really handy with a set of extractors, don't try this on a lock you are keen to re-use, as the broken keys are somewhat tricky to remove.)

That was me as Guest.

Made another attempt at printing the Kryptonite keys more slowly. It works as smoothly as the ABUS key now.

the printed key activates the discs, torsion isn't a problem in that area. The flat piece of metal doesn't need to reach all the way into the lock itself. (think about lock picking where the torsion wrench is only just inserted into the opening.)

Shoes showed me this the other night. Very cool. 8-)

Try superglue flooding for better strength, and make the top of the key shaft, were it meets the bow, a bit wider.

Going to try this now on my UP!

nrp - in reply to healthy

You may be thinking of wafer tumbler locks, which just need torsion on the cylinder. On disc detainer locks, the discs are the cylinder, and you actually do need torsion strength across the length of the key.

healthy - in reply to nrp

ah, yup. thinking of wafer. well good luck, the only thing else i can think of is coating it in something that will dry stiff. it won't add much strength in and of it self but maybe it can keep the layers from starting to delaminate. not sure what your failures are looking like.

How about embedding some stiff wire in it? I was thinking you could print this with some grooves or, if your printer can manage, channels for a straightened large paperclip.

The trouble is torsion. A slot to fit some rectangular piece of steel could work, but I'm not sure there is a spot to fit a channel like that in the model. Too much is already cut away for the bitting and warded discs.

Acetone treatment seems to make ABS a little stiffer. Also, PLA is more rigid than abs. You might also get less flexing out of either plastic if you stick it in the freezer for a while before using it.

I was using PLA. I'll try out the freezer.