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Old 03-20-2018, 11:45 AM
Teddy Bear Rat Teddy Bear Rat is offline
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Some time opened up for me the other night, so I was able to make progress on the octagon barrel. The first thing I had to do was machine the top, leaving enough material for the front sight ramp. Doing this made the rear of the barrel a perfect square, so placing the piece in v-blocks would allow the next two flats to be machined at the proper angle to form an octagon shape:


The problem was the vees in the blocks are too deep, covering the area needing machining. I thought about shims but ended up cutting a groove across some square aluminum from my too long barrel wrench. By holding the aluminum stock in the v-blocks, the groove is formed at a 45 degree angle:





That left doing the two remaining flats, which could now be machined by simply clamping on the proper flats in the mill vise:




The glare from the flash doesn't show the nice flats that well, but you get the picture...no pun. I left the barrel under-rotated by one turn, and I still need to remove maybe .010" from the bottom to get the ER to clear, so the cylinder still will not lock up yet:





This is as far as it goes tightening by hand:


Honestly, some of the flats are off by a .001" or .002", classic tolerance stacking, and probably from the makeshift aluminum v-blocks, but I cannot see it without precise measurement. Stoning would likely make it close to perfect, but I'm not sure how important that is, since it looks true to my eyes. I used to think I could see .001" in a workpiece, but maybe not anymore.

The next step is to relieve the bottom so the cylinder can latch and machine the sides of the front sight ramp and ER block vertical (I intentionally positioned the edge of the end mill so as to leave as much material on the sides as possible):


So, then I'll need to decide about subtle contouring around the front sight ramp and the ER block (radii vs flats), and, with some help from the my brethren here, what kind of front blade I should machine it for. The current S&W format would work, but a hand-made dovetailed blade would look better, if not as versatile. I welcome any suggestions on the sight blade.

BTW, the revolver now weighs 1.5 ounces less than it did with the original 4" barrel. The remaining machining may drop an ounce (probably less), but the look and increased compactness make this all worth it to me.


TBR
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