Building Your Own Medecoder

There have been lots of request for more information about building this tool. I will provide as much as I can here so that others can experiment with this style of tool and technique. I encourage the folks reading this page to use what I've written as merely a guideline and to try other things (materials, sizes, features, etc...). Our goal for this page is to build one of these tools that is functional and cheap. Also, we will be using materials that relatively easy to get ahold of. There will be no machining or special tools involved. Some folks out there may question the ethics of posting this information; this is a valid discussion and I encourage them (and all of you) to email me. My stance on this issue (disclosure, etc..) in this case is that the amount of practice and skill involved in using the completed tool mitigates any public safety concerns created by this page. Also, I would greatly appreciate it if the information used on this page were not used for commercial purposes.

Materials and Tools


This is the part of the tool which you hold and use to hook into the sidebar grooves. It consists of an X-Acto knife handle with a piece of bent 0.020" diameter music wire clamped in it. One also may be able to use a pin vise for this purpose, but because we are going to be epoxying the wire into the handle, X-Acto handles are good for this use (cheap and disposable).

Scale Tube

The scale tube is used during picking and decoding to determine how far the groovegrabber is inserted into the lock. The groovegrabber slides inside the scale tube. When the user wants to measure the depth, they slide the scale tube against the plug face and compare a scale in this tube to the index mark on the groovegrabber.

Drawings and Measurements

For further reference, here are some measurements. Click the thumbnails to get the full-size images:

Tballard was nice enough to whip up a few scales on a PDF. These should print at the appropriate size on any computer and printer.

Successful Builds


The Medecoder I built relied heavily on JK's plans, and throws in a few minor tweaks. The most noticeable is the engraved flat stainless steel scales. These are made from strips sourced from windshield wiper inserts, and the cuts were made by taping the inserts to a paper scale, and scoring them with a needle file. The scale tube itself is double thickness, and the window was filed down enough to provide a shelf to fit the scales into, with the overhanging portion filleted with JB Kwik epoxy. (For those sharp-eyed readers who wonder why there are seven ticks, the answer is that I can't count... opps) The groovegrabber is also slightly different in that hobby-knife blade handle is only epoxied into the back section of the handle, and the collar for the collet is epoxied into the the front of the scale tube. As a result, the rear section can be twisted to loosen and tighten the collet, allowing the probe wire to be adjusted or replaced after construction. (The collet which comes with X-Acto pn: x3201 is slotted, but I was able to find a generic hobby knive with an "X"-shaped collet, which makes centering and clamping the wire much easier.) The other thing I did differently was the initial calibration. Even though my wire is adjustable, I prefer to not mess with it, so the technique I used should work for fixed-wire designs as well. What I did was build the entire tool first, and then mark the groove grabber with a normal ball-point pen when I calibrated it. This mark is temporary, but good enough to test out all the various positions before commiting to something more final. Once I was happy with the ink mark, I used a micro-tubing cutter to score a circle around the tube, and then used a variation of the "drill and cutoff disk" method JK recommends. It was a lot of fun to build this tool, and I'm sure it is the first of many to come.


My Medecoder build went well, I tried not to deviate from the original plans too much just in an effort not to screw things up too badly. My main problems were during the cutting of the slot on the measuring tube, its rather hard to cut a straight slot with a Dremel but after 2 tries I got it close enough. The calibration was also a bit of a pain, I chose not to use the paper scale and to draw my own, but as I found out it is very hard to draw 6 lines that are exactly the same distance from each other. However, even though my lines weren't exact the tool still works perfectly because of the sidebar leg tolerances. A small improvement that I think people could implement would be using a tubing cutter to make the engraved ring on the 'groove-grabber', because the drill and Dremel approach is rather awkward, though effective. I also used a wire wheel to buff the entire tool, before calibration to give it a smoother glide and make it shiny. Overall, I had a lot of fun making it and the tool is very effective.


With my deepest gratitude to the inventor of this device JK. for so many years, i planned to pick this Medeco thing that stop me is the side bar. until i saw JK video demo.thinking of mat.same w/ JK proj.i have none.but considering my thoughts , that just as long that i will be within its principle i can use any material that fit and modify. here is the product of my interest. and for a long yrs.this is the first time i ever pick a medeco cyl. and i succeeded with the Medecoder Aid.see pics for those interested to make isnt hard as it look. & my help is available,all the way. The perfect material:1medeco,1solid aluminum plug follower ,3semi fine thread screws,1spring.