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Old 02-19-2014, 08:58 PM
Bob Smalser Bob Smalser is offline
 
Join Date: Apr 2013
Posts: 32
Default An Improved Rifle Rack for Offhand Stands



As an ex-Army competitive shooter who is now a volunteer coach for a large junior program teaching Olympic small-bore, Iím constantly looking for ways to reduce the distractions and inefficiencies of match preparation, and getting the rifle off the ground to speed buttplate and sight adjustments is an excellent example. While there is at least one commercial model of these ďantlerĒ rifle racks available, it is unpopular with our advanced shooters and coaches because its design allows the rifle to spill out of the rack should the arm screws come loose, and is considered too flimsy in construction, making the offhand stand easy to tip over and easy to damage the standís shaft by over-tightening the set screws. As a boatbuilder by training who often has to fabricate custom hardware, I designed and made another thatís a bit heavier and shorter, grips the much stand better, and is totally spill-proof. Itís been surprisingly well-received, so I prepared this tutorial on making one in a modestly-equipped home shop, as there are far too many operations required to make this a profitable venture for any but fully-equipped commercial machine shops with forging and casting capabilities.



To improve gripping the offhand standís easily-dented aluminum shaft, I increased the surface area in contact by using thicker stock for the base, and shown are 1Ē-thick aluminum plate scrap acquired locally. Three-quarter inch thick would also work well. Also shown are the remaining materials necessary to make these - half-inch aluminum rod stock, thick-walled latex surgical tubing of half-inch inside diameter for padding, and a handful of assorted-length ľ X 20 thumb screws through one-inch. (Aluminum doesnít like fine threads.) Alaska Copper in Seattle or McMaster Carr in Baltimore can supply new plate, Tacoma Screw or Home Depot the rods and hardware, and eBay has a good selection of latex tubing. Local scrap yards can also be excellent sources of materials, especially for the heavier stock that can be expensive to buy new and ship. Finding one near a shipyard or other major manufacturer can be very rewarding, even if you have to do business via telephone and UPS.



I cut the plate into rectangles of 2 X 5 3/8 inches on a power band saw with a bimetal blade. You could also cut the stock by hand using a hack saw or take it to your local metal fabricator and pay to have it cut to your specifications. Length isnít critical plus or minus a half inch Ė I selected 5 3/8 based on the capacity of my drill press. Lubrication isnít absolutely necessary when cutting soft aluminum, but can speed things up and extend blade life.



I clean up the bandsaw marks by taking multiple, 1/32Ē trimming crosscuts using the miter gage and a carbide-tipped blade in my table saw. Care is required, as are adequate safety glasses. Donít expose any more blade above the saw table than necessary, because like in any table saw work, itís only the carbide teeth that do the cutting. Feed the workpiece sufficiently fast or misaligned so that the stock you are cutting comes in contact with the steel saw plate instead of the teeth, and the workpiece will be thrown with great force. And donít even think about making this crosscut soley on the table saw, as you canít feed material this hard into a table saw by hand with sufficient consistency to avoid it being thrown.



Next, I lay out my stock for drilling for the arms, allowing a quarter - inch thickness remaining in the walls so they can take holes and threads sufficiently strong for set screws to hold without stripping.



I drill the half-inch holes for the arms in three incremental passes of increasing size, flipping the workpiece to drill from both ends. This is based on the depth and power limitations of my radial-arm woodworkerís drill press, but incremental drilling of long holes generally allows for a more accurate hole, as the larger drill sizes act as reamers, following the original pilot hole.



Iím very careful to use low speeds and not to take more bite with the drill bit than the bitís flutes will clear the waste from, plus I clean the chips from the workpiece and flutes as I go. This usually means quarter-inch bites to begin with and eighth-inch bites as the hole deepens, covering and filling the clearance flutes with chips. In this job, as the arms are inserted into the base from each end, perfectly-concentric holes arenít absolutely necessary.



After drilling for the arms, I center-punch dead center of my base stock for the 1 1/8Ē shaft hole necessary to fit the offhand stand, a hole that will be drilled with the arms mounted.



Next, I begin the process of bending the half-inch aluminum arms using an oxy-acetylene torch. This requires some practice, as aluminumís temperature increment between being sufficiently hot for easy bending and crumbling from too much heat is small compared to bronze, brass or steel (which are adequate but significantly heavier alternatives for those who have trouble getting the hang of aluminum.) The technique here is to use an acetylene-rich flame to smoke the rod, followed by adding oxygen so as to heat the rod slowly with a neutral flame to the point where the flame burns off the soot. By moving the flame gradually up and down the rod to clean it, the rod becomes uniformly heated to the correct bending temperature when all the soot is removed. For those without an acetylene setup, MAPP (or probably even propane) gas can also be used if you first soot the rod using an alcohol lamp burning mineral spirits like in fitting the swamped barrel during the antique stock repair shown below:





When the rod is at the correct temperature, it is simply placed in the jig and bent. As the rod tends to slide along the fence as itís bent, the pencil marks where I place the end of the rod in the jig. I find half-inch rod likes to be slightly hotter than the soot burn-off point for optimum bending of perfect curves, but as overdoing the heat will result in failure, usually itís better not to risk overheating. Any unfairness in the resulting curves can be corrected later by cold-bending over a mandrel with the aid of a mallet. Better jigs can be made from other materials, but wood is cheap and easy, although because it chars and gouges, a metal fence is required for multiple bends. Here I use two diameters depending on the rifle Iím making these for Ė 2 ĹĒ and 3Ē, the three-inch being the more versatile.



The rod it reheated using the soot technique, and the next bend is made in a simple, 90-degree bending jig made from square stock and drill rod, the blind holes silver-brazed for strength and spaced to tightly fit the rod or flat stock.

Continued...
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