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4575wcf 06-19-2020 08:19 PM

Making the LC Smith rotary bolt--milling the trip detent notch-part 3
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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!

4575wcf 06-26-2020 11:08 PM

Prepping the Rotary Bolt to Cut the "Tooth" Part 1
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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.

4575wcf 07-16-2020 05:04 AM

Hey all
This has been an interesting last three weeks. Our local sawmill has been down off and on with a series of large broken power transmission shafts; a few mornings the maintenance man has met me at the front door, sketches in hand. Suffice it to say the DRO equipped milling machine has been tied up, with the vice removed. We are about dug out now. Such is the life of a small town machinist. Other things are in the works here at home, my wife and I have found an antique house to be moved. Our existing antique house has been treated pretty roughly over the last century, and this one is very similar in size, style, and vintage, but in much better shape. Everything is in order, we are only waiting for the movers to give the go ahead, yes or no, then it gets BUSY. Saving a nice old house from the wrecking ball has been on our bucket list for some years, so this is exciting. We will keep Rusti moving along too in spite of all though. I have completed the math and drawing for the angled milling cut in the rotary bolt to my satisfaction with the numbers all worked out. I will be making this cut as soon as the vice goes back on the mill table and we get enough of a lull in the action. Thanks all for your patience.

4575wcf 07-21-2020 08:37 PM

LC Smith Project cutting the "tooth on the rotary bolt" part 1
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Hey all
Things came together this morning at work and I completed the angled cut on the rotary bolt. It was a pretty involved cut to make in an hour start to finish, I got it out okay, but the photographic record suffered. I will repeat the set up tomorrow morning and get some better pictures.

To begin, here in picture #1 is my completed math. Measuring the slot at the beginning of the tooth and at the end of the tooth gave us the change in "x" along the angle or .0625. Measuring the length of the cut around the curvature of the circumference of the bolt gave us the change in "y" or .500. Right Angle Trigonometry gives us the angle, thus side a/side b =<tan or 7.125 degrees. We have 16 increments of .032 each marked out on the bolt. We will use line 0 thru line 14 measured to the center of the cutter, lines 15 and 16 would overcut into the part, so we must stop there and not use these last two. Cutter diameter is .125 so we must add half this diameter to move our end mill over to the right side of the cut. .020 is added to give us a finish allowance along the tooth surface for fitting later.

Therefore our equation states "For increments .03125 each increasing in y from increment 0 to 14 thus inc #/32 *( sin(7.125)) + .240 +.02 +.0625 equals distance in x" .24 is the actual tooth thickness + .02 is the finish allowance +.0625 is the cutter radius. The resulting x values in our table are the location for each cut plunged along the 1/32 divisions of our angle (vector).

Next we use an edge finder to locate our back vise jaw Picture #2, and enter positive .100 into the DRO in "y'" axis. Picture #3, Bring the edge finder up and move to zero, Picture #4, then move in -"y" to half the bolt diameter (.343) and zero the DRO out precisely in the center of the bolt in "y" axis

We have set a stop to the end of the "drop" so the bolt can be loosened and rotated in the jaws and still closely maintain its position in x

Next up. . .edge find the front of the bolt, turn the bolt and align the first index line (#0)to center, and move to the x location for the fist cut.

4575wcf 07-22-2020 08:39 PM

LC Smith Project cutting the "tooth on the rotary bolt" part 2
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Hey all
I made it into work an hour early this morning and "re-enacted" the angled cut on the bolt to get some decent pictures.

The front edge of the bolt has been found and the center of the cutter located on that edge. We move to the first x value on our table at x -.322, bring the cutter down close to the scribed line, then rotate the bolt to center our first scribed increment. Then we carefully plunge the end mill down into the inside pocket. Back up with the end mill, move the mill table to our next value of .326. Loosen the vice, rotate the bolt to the next scribed line, clamp the bolt in the vise and carefully plunge down into the inside pocket. This process is repeated until scribed line #14 is plunged. Then our end mill is moved out to the outside edge of our slot, already calculated at x-.3917, and the process repeated in reverse rotation with no changes in x until we have cut our way back incrementally to the zero scribed line, point of beginning. Pictures #1 through #4---Move x, rotate bolt, plunge cut, Move x, rotate bolt, plunge cut. A pattern begins to develop and we see about a .004 change in x for each increment plunge begins to build our angle. Then out in to the other side of our notch, and cut the straight back edge of the notch in reverse.

4575wcf 07-22-2020 08:54 PM

LC Smith Project cutting the "tooth on the rotary bolt" part 3
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Here is the notch finished as far as we will take it for now. Picture #1, Once the new monoblock is made and the barrel assembly is jointed to the receiver, the rib extension will be fitted to the new bolt and both the tooth and rib extension surfaces will be mated at that time. Best to not get too far ahead of myself and become overwhelmed, so for now we will concentrate only on getting the drop sawed off the bolt, pictures #2 and #3, then get the back solid side of the bolt faced in preparation to make the final two cuts.

Next up. . . face the bolt to length, set up the original bolt in the mill, and find the exact location for the .250 diameter pocket that accepts the coupler stem from the back.

4575wcf 07-22-2020 09:22 PM

And now, a minute to tell on myself a bit
This post is specifically designed for the somewhat advanced gunsmithing student, like myself. I am gaining in LC knowledge all the while, but very much learning on the fly, thus I have passed a couple of inaccurate statements along. I am a stickler about this, the whole gunsmithing world is fraught with inaccuracies it seems, so to rectify:

1. Earlier in my posts I indicated the difficulty of getting the bolt seat machined in tight under the tang. In fact, the seat was cut first, requiring only an extended toolholder, and the tang was then bent down as observed in the engineering drawings available at the LC Smith Collectors site. This made cutting the seat accurately a WHOLE bunch easier, believe me, but at the same time most forgings are forged directly to shape. Whether bending the tang as a second operation, and then "freezing' it in position during case-coloring caused issues with the future "unbending" of the tang in time, I do not know. It is a question I will be running by the Practical Machinist forum.
I understand absolutely why they did it this way, I am just not sure if it cost them any integrity in the stiffness of the tang.

2. I missed the secondary notch on the rotary bolt. The tooth does slide through a hole in the rib extension as I indicated, but the back of the inside pocket behind the notch also slides over a flat on the end of the rib extension. This provides another locking surface, but a very small one. I missed this simply because I do not have the barrel assembly on hand and in front of me. These are the first retakes, no doubt more will be revealed as we move along

4575wcf 07-23-2020 04:58 PM

LC Smith Project--Face the Bolt to Length and Locate the Carrier Stem Holestem
5 Attachment(s)
Hey all
This morning first thing I set the bolt up in the small lathe and faced it down to finish length of .630. Picture #1. I then set up the original bolt in the mill vise, stood on parallels with the notch clamped against the movable jaw. Looking at the bolt in this view we would be seeing the bolt from the top down in the unlocked position as viewed from the back. Using the coaxial indicator the outside diameter of the bolt is swept in, and the DRO zeroed at part center. Picture #2 The 1/4 inch diameter counter bore in the back of the bolt is a clearance cut for the stem of the coupler, which extends into the angled stepped holes directly underneath it. Picture #3. The hole is "picked up" with a matching 1/4 " end mill, while the DRO tracks our movements. The hole is found to be at .0938 (3/32) from center in both x and y indicating a 45 degree angle from center in x and y positive. Picture #5. Good thing I checked this I had guessed the position at 30 degrees on the print--a ways off.

Next up. . a closer look at the back of the bolt, the straight clearance counter bore, and the angled stepped holes underneath it and some modified tooling to put these cuts in.

4575wcf 07-27-2020 10:15 PM

LC Smith Project--Preparing to drill the back side of the bolt
5 Attachment(s)
Hey all
Spent this morning early at work putting locking system pieces together and taking pictures. I got about 3 posts worth. It is time to add a few parts and put a little life into this build, I almost went to sleep myself getting through the front end of that ornery rotary bolt. Okay here in picture #1 and #2 is another couple of pictures trying to get enough light down the carrier stem hole to show the two angled holes. Not having much luck, my camera eqiipment is far from the best. Picture #3 shows the angle that the coupler is engaged into the bolt when the top lever is centered. This is one of the tricks that makes the whole system work, the coupler is engaged all the way right, then swings over at a downward angle to the matching angle 90 degrees left. Corny, but the best way I know to describe this action is to hold your pencil in the dead center of your happy face, angle down, and draw the mouth right to left. That is probably the only way to transmit motion to a rotary bolt with a very tight radius by moving a top lever directly centered to hard right. That it works at all is incredible, how smoothly and well it works under the strong spring tension as it is under- -well that is kind of hard to grasp. In picture #4 the parts are stacked as they are assembled. The 1/8 diameter stud on the front of the coupler does all the turning of the bolt, fitting into a downward sloping hole in the back of the bolt with enough clearance to adapt to the constantly changing relationship between the two parts. They are--quite simply--operating on two completely different tracks. If I was the manager when Brown brought that Idea around I would have bet him lunch and $50 it would never work. Picture #5 shows the assembly together outside the shotgun, assembled with hardware mush bolts. The wonderfully standard LC accepts them readily, and they will do all the giving, leaving us nice theaded holes when we build the real gun screws and time them toward the very tail end of the build, of course only after we assemble and dissassemble her a few more hundred times.

4575wcf 07-29-2020 05:21 AM

LC Smith Project--The Triggerplate with Top Lever Lower Bearing
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Hey all
Picture #1 is the used and somewhat abused trigger plate that will be fitted to Rusti. I believe this plate to be from a regular frame LC circa approximately 1907. The trigger plates are not considered interchangeable between the two frame sizes. As you can see someone has drilled a small hole into the side. I wrote into the Practical Machinist Forum and got some input on how to properly repair this damage. Since the trigger plate will eventually be color casehardened to match the receiver, the correct fix is to drill the hole out to slightly larger size and give it a slight countersink. Then a mild steel plug is turned and seated into the hole somewhat proud of the surface. No TIG filler rod is needed, and the two parts are welded in place using that part of the plug extending above the hole as the necessary filler metal during the weld. The exiting outside profle fit between the receiver bottom cutout and this trigger plate is very good, Picture #2 ;however, about .02 will need to be removed from the mating top surface of the plate. This will close up the gap between the bottom top lever bearing hole and the top lever bearing stem, Picture #3, and bring the plate up flush with the receiver. The two tang screw holes line up perfectly, so I believe this slight difference in thickness is the only real difference in the trigger plates between the two frame sizes at this particular time in manufacture. Pictures #4, and #5. There are variations in the trigger plates depending on the year of LC manufacture, but these both were made with the single screw hole in the rear tang, and with the rear safely hinge lug behind the trigger block, I believe, and can be fitted up with all parts, and made to work just fine. I bought this plate in a parts lot on ebay, after examining many pictures online and familiarizing myself with what the missing trigger plate should look like. I got lucky with the fit, ie. what does not fit well can be made to do so. Once this plate is repaired and fitted up, and the back side of our new rotary bolt is finished, I can get the new rotary bolt fitted and functioning with the original coupler and top lever. When that is accomplished, I can then build the coupler new and get that part working. Some attempts were made to free the rusted components at some point before Rusti came to me, and the coupler yoke surfaces were somewhat battered. This part of the project is all about closely examining the parts as we go, and repairing/replacing and setting right every defective part.

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