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LC Smith Project Gun Starting From Scratch

This is a discussion on LC Smith Project Gun Starting From Scratch within the High-End and Specialty Shotguns forums, part of the Shotgun Forum Discussions category; Hey all Here in picture #1 is the old and new bolts with the trip notch cut completed. Picture #2 is the original bolt viewed ...



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Old 06-19-2020, 08:19 PM   #21
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Making the LC Smith rotary bolt--milling the trip detent notch-part 3

Hey all
Here in picture #1 is the old and new bolts with the trip notch cut completed.

Picture #2 is the original bolt viewed from the bottom with the original trip placed as it lies when it is pushed into the notch by the trip spring. Note the small amount of clearance around the trip, shown bottomed in the notch. This is a result of wear caused by the opening of the action, who knows how many times during its service life. Curiously, the bolt notch did all the wearing, the trip itself showing almost none. The result of this wear would be for the bolt to lock up on the trip in a less than fully rotated position. This in turn would cause an ever increasing misalignment of the slot where the rib extension drops through. This would cause a bit of rubbing where the rib extension and bolt contacted, and indeed the original bolt shows a mild wear pattern confirming this. The original barrels with the rib extension integral are long gone, but the side of the rib extension would have been scuffed as well.

Picture #3 it appears our 15 degree angle was the correct one, for the fit is considerably better between the original trip and our new notch. Indeed this trip could be used as is with our new bolt. The trip is such a minor part to build though we will get one out, and remember this one was rusted in solid. The trip, and its seat are a bit pitted. Also it did not come out easily, requiring more than a few gentle whacks with a brass punch, so the surface finish has suffered some.

The trip and the bolt should have been made to the same hardness to wear equally. The trip was obviously the harder part, since the bolt did all the giving. Neither of these parts are intended to be removed during the service life of the shotgun since the carrier screw gets peened over to discourage disassembling them. Our parts will be made from the same stick of material, it being prehardened. Also note the difference in the back end of the notches, the original being tapered where the formed cutter made the straight and angled side in one pass, and ours being straight due to taking two cuts with the same cutter in different planes. Only the front 1/8 inch or so of the notch bears on the trip, so this effects nothing, but the original cut looks a bit better at least in my opinion.

. . . next up cutting the "tooth" without a rotary table--bring on the Vector Calculus!
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LC Smith Project Gun Starting From Scratch-dsc03382.jpg   LC Smith Project Gun Starting From Scratch-dsc03384.jpg   LC Smith Project Gun Starting From Scratch-dsc03386.jpg  

Last edited by 4575wcf; 06-19-2020 at 08:37 PM.
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Old 06-26-2020, 11:08 PM   #22
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Prepping the Rotary Bolt to Cut the "Tooth" Part 1

Things are getting busy at the shop, the haying season is in full swing and the agriculture repairs are rolling in. There was not lots of available time to work on Rusti this week, but I did do some figuring in the mornings about how to machine the locking notch in the rotary bolt. I think that the best way to approach this rather complicated helical cut is to mark a series of chord measurements around the periphery of the bolt. These can be picked up with a pointer as the bolt is rotated around in the vise jaws by hand. A hard stop set to the back of the bolt will allow rotating it and maintaining its position. Vector calculus will provide the correct dimension to distance the cut away on each line as we index around, using the one milling machine we have that is equipped with a DRO (digital read out).

The first problem was to lay out a series of accurate scribed lines along the barrel of the bolt .032 apart. Attempts to do this by hand were less than satisfactory so I cooked up this method which worked very well. First we consulted the Machinery Handbook and used the provided table to find a chordal measurement that was a good fit. 68 equal spaces worked out about right on the .687 circumference. I attached a strip of electrical tape to the chuck marked off at the same 68 spaces on the larger diameter, improvised a pointer, and then scribed the bolt along a "straightedge" improvised by a piece of keystock placed in the toolholder and held tight to the bolt.

This method allowed very accurate graduations to be scribed along the length of the bolt. See picture 2

. . . Next up--Calculating the tool movement in the "x" axis to comply with rotation.
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LC Smith Project Gun Starting From Scratch-dsc03387.jpg   LC Smith Project Gun Starting From Scratch-dsc03388.jpg  
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