I used to struggle with this issue: aligning the hammer cup with the nipple on Hawken builds. I would have to stretch and bend hammers to make them 'right', but not anymore.
The following is how I go about this job.
I'm going to back up a bit first and talk about the castings that we have available in general. First the breech plug and tang are not finished, as received, at least any that I have been able to work with to date. The breech plug and tang has been cut for the nipple seat, and a nipple will fit, but is impossible to get a wrench on because of the excess metal in the snail. A few layout lines and some work with a Dremel and stones will take care of that in quick order, though speed is not what you should be after. Lots of original Hawken breeches are cut well into the plug giving ample access for cleaning and nipple work...I stopped right at the edge of the top flat's right had periphery.
While were looking at castings and how to make them better and more authentic, let's examine Davis' hammer. I have never found images of an original Hawken rifle with a hammer of that shape...it is too voluptuous. But again, some layout lines and work with files will give the hammer more grace, and make it more like those found on original examples. The hammer cup on the casting is too shallow. I ground a drill bit with a bit of taper to the tip, and a flat end to deepen the hammer cup without making the rim too thin and fragile. One can also use the bit to change the angle of the base of the cup to strike the nipple at exactly ninety degrees. Somewhere I have pictures of that process, and I'll try to add them if I can retrieve them.
Now that the breech and hammer suit the build, I align the lock so the hammer cup aligns with the nipple, and mark the plate for the extremities of the snail. I use various files, mostly this 1/2" rat-tailed behemoth to hog out the plate. Go slowly, and use transfer colour to get a perfect fit and alignment. This is critical for success in the alignment deal.
One of the issues with Davis' lock and the breech castings commonly available, is the plate is too thick at the bolster to allow the hammer to come over to the nipple. This causes an additional problem in that the plate sticks out from the side of the snail. The bolster thickness on the Davis lock is thick enough to allow you to taper it, removing metal from the aft' end, so that by the time you get it flat and true, the plate moves over closer to the barrel, the snail protrudes just the right amount, and the hammer miraculously aligns with the nipple, without bending. You also achieve that narrower after end at the wrist, and flared for'd end, common on S. Hawken rifles. This bolster tapering is best performed AFTER the plate has been cut for the snail. In these images, I've simply set the lock alongside the barrel, and the mainspring pressure holds everything where it will end up on the rifle...perfect alignment, and no angst getting there.
..hammer down, and hammer at half bent...
Now, it is a simple matter of inletting the lock so that the plate fits tightly against the snail, and you know all is going to be in alignment.
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