Carrying on from Part 3, here’s a picture of the process to make your tensioner.
As described in there, you can use a blank to make a tensioner, rather than needing a CNC machine – after all, it already fits! Even better, many locks come with a key that works! If it came with 2 or more, result!!
Below, I am using a blank key, if I recall correctly, but a cut key would be exactly the same process, with a little less metal to remove.
This is a pipe key, so there’s a hole in the tip, and we are making a Hobbs pick, effectively.
Once the flag is cut back to the shaft of the key, leaving just our tensioner part, we need to go deeper. We still need to cut away metal so that the picking wire can get access. So, do just that – keep filing.
Once you are at this stage, you might find you go all the way through the top edge of the blank. Don’t worry, you are trying to make room for the picking wire, and this is as far as you can go without attacking the lock with tools. The tensioner will still have plenty of strength. Try to angle the filing cuts so that you do limit the material taken away though. You want it removed where it matters most, which is just at the entrance to the keyhole, and a little in front, and then all the way back to the tension part you left in place from the flag. Try to take into account where the wire will be relative to where the tensioner will stop. I like to try and leave a smooth flat surface for the wire to move easily on.
You can bend the shaft to 70 to 90 degrees cold in a vice.
A commercial tool on the left (Stainless Steel) and two I made myself (from keys that clearly weren’t!) – a Hobbs style from a short pipe key with welded on handle extension, and one from a longer pin key that doesn’t need any extension. Rightmost is a double ended, single bend, picking wire. You’ll notice I went all the way through the wall of the pipe key, and it makes no difference as there’s still plenty of metal on the far side to provide the required rigidity.
Refer back to Part 3 for the wire bending. You’ll likely only need a basic single bend, as shown on the right, for a key and lock like this, as the drill pin precludes the existence of a curtain, mostly.
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