The target locks (which I own) are 7-pin BEST SFICs; the blanks I'm cutting from are non-OEM, but correct (G) keyway. Since I don't have a micrometer or calipers, I've used my set of operating keys and a ruler as reference for spacing and depth.
The nut of my question is: What's the ideal way of shaping the peaks and roots of a bump key for a BEST SFIC? What should I be doing differently?
I've done my best to space the roots at .150” (3.8mm) from center-of-cut to center-of-cut. In terms of positioning the cuts properly on the blade, I first eyeballed the operating keys for reference, then used a round file to make cuts that were almost a 9—but not quite that deep.
Figure 1.Then I referred to the table of A2 bitting and pin specs published in the April 2008 issue of ALOA's "Keynotes" (page 26). I measured the proper distances for each cut from tip stop to bow, and marked each position with small hatches/notches along the lower blade. I then then used a #0 pippin file for the finer work of shaping roots cut to a depth of "9" that hit the center of each reference point I'd measured and marked earlier.
I then filed back the tip, the tip stop (on the bottom), and the shoulder—so as not to break anything.
My first stab at hand-cutting this bump key was premised on filing roots and peaks approximating the geometry of a "99" that appears on one of my OEM operating keys (See Figure 1, specifically, the biting in the top (OEM) key for pins 6 and 7), consistent also with a machine-cut BEST bump/depth key I saw online. In other words, I tried to make flat roots cut to "9" and peaks as symmetrical as my tools and hands allowed, like so: ^-^-^-^-^-^-^-^.
Figure 2.I attempted bumping with it; no joy.
My new theory at this point was that I'd shaped the peaks a little wonky (none were a perfect 45 degrees), and that my "9" cuts should have been deeper. I also read a different (competing?) strain of thought regarding the ideal shape of a BEST bump key: Since SFICs favor the "pull back"(/"one click") bumping method (according to TOOOL and—as I recall, though perhaps falsely?—other posts on this forum), the bump key's roots should be cut slightly deeper than "9", and should not be flat. Instead, the peaks and roots should form a shape that looks like this: ^^^^^^^^.
So I modified my first (unsuccessful) key accordingly.
Figure 3.That didn't work either.
As you can see in Figure 3, the (re)modified key has roots cut below "9" depth. You may also notice the peaks are not very high (relative to an imaginary plane set at "9" depth), and conjecture that the peaks are too shallow/small or spaced to transfer the striking force. While it is entirely possible this is the case, I should note that I've watched and felt how the #7 pin (the pin most anterior to me; i.e., closest to the bow) moves over each peak as I insert the key into the cylinder. From my observations, pin #7 (from which I'm generalizing about the rest of the pins) still moves a considerable amount vertically over each peak, and presents what would seem to be an appropriate amount of tactile resistance. I also don't feel any loose play between the pins and peaks when the bump key is inserted at the "pulled out one click" position.
TECHNIQUE: I've tried bumping my BEST SFICs both dry and with WD-40; in rooms with warmer and colder temperatures; using the bottom of a stapler, a screwdriver handle, or wrench; without anything around the bump key's shoulder and also with a rubber band, or a bicycle inner tube, or foam earplugs. I've refrained from turning the bump key prior to the moment of contact, so as to avoid binding the pins.
No success yet. But I know this thing is bumpable. I believe it's the key, not me.
QUESTIONS: Please have a look at the photos; tell me what you think:
(1) What's the ideal geometry for a BEST SFIC bump key's biting? Flat roots or "V-cut"? To what depth? How about the first peak—bigger, smaller, same size?
(2) What have I done right, and what have I done wrong?
(3) What must I do to craft a bump key that works on a BEST SFIC? (...Ideally using only the resources I've mentioned earlier.)
In advance, thanks so much for your advice and experience.
