Once I have a good rod fit, I mount the arms to the base by drilling, tapping and fastening using thumb screws. How you do this isn’t critical, but these are blind holes that only penetrate to around ¾ depth of the arms. What is critical is that the arm ends touch each other and meet in the exact center of the long hole, and that’s why I laid out and marked them using masking tape.
Once I have my base holes tapped for the thumb screws locking the arms, I ream the holes in the arms made by the tap drill to half depth using a quarter-inch clearance bit. The resulting stepped hole provides me some “squish” to overtighten the thumb screws if necessary to clear the rifle when mounted in the stand, without damaging the threads.
There are a couple of options for boring large holes in aluminum, brass and bronze in small shops. One of the best is a carbide-tipped hole saw designed to bore steel, but these cost around 50 dollars if you only expect to perform this job once. Another is boring a clearance hole followed by a heavy-duty 3/8” or larger router using a carbide-tipped straight bit, using multiple tiny passes of around 1/32” against a scribed circle. Either way, it’s useful to have both, as like aluminum rod, hole saws and offhand stand shafts vary slightly in size by manufacturer, and the router is an efficient method to ream an undersize hole.
So with the arms firmly locked into their final positions, the 1 1/8” shaft hole is bored…
…the result being the arms are locked in place by the shaft and not merely by the set screws, making the rifle rack totally spill proof. On the bench you see the stand’s shaft and the router with a straight carbide bit. Here I’ve already cleaned up the hole using the router and fitted the shaft so it is snug but can slide without binding. If your arm holes are sloppy, you’ll have trouble with the hole saw catching and stalling trying to drill through loose arms. The solution is to drill the base hole without the arms, and then mount the arms to finish the hole and cut the arm-end profiles using the router.
Next I lay out the base to its final shape…
…drill holes in the inside corners to ease the task of making clean, interesecting sawcuts, and cut the base to its final shape.
The holes for the shaft set screws are laid out…
…and drilled and tapped using a level when necessary to insure all holes are centered and plumb.
The base is cleaned up by drawfiling to any level of finish desired, all edges and corners eased using files…
…and a simple brush finish applied.
Last, the rods are cleaned up using files, the sections to take the latex tubing are buffed to a high shine using an 8-inch power buffer and green rouge…
…and the tubing sections worked on using Armorall liberally as a lube. This can be the most difficult task in the project, so don’t omit the polishing, even if you have to do it using Brasso by hand.
Final test assembly on the bench reveals a snug hole that will grip the shaft snugly with minimal torque on the set screws, yet will also slide easily when the screws are loosened.
Double checking it at home on an Annie 1613 in the high position shows it to be a good fit to the rifle and fully functional. To gage sizes, this particular stand was made with 2 ½-inch diameter arms covered with 8th-inch thick latex tubing, and fits the rifle snugly.
Regards,
Bob Smalser
Seabeck, Washington
http://www.wkfinetools.com/contrib/b...lser-index.asp
Reply With Quote