RCA #43 has a gold touch hole that is believed to be original to the rifle, and I wanted to reproduce it for my gun. Doing so was probably one of the most tedious and stressful tasks accomplished so far on this rifle, as most of the process was new to me. The gold touch hole is essentially a high dollar rivet with a hole in the center.
I created a couple of special tools along the way to overcome some of the problems associated with riveting through a barrel wall, and did some smelting and casting. I'll try to explain how it was done with the help of a few photos.
The first order of business was to drill a 3/16" hole in the barrel, then counter sink the outside to 1/4" diameter.
Then I used one of my home made tools from the previous post with a hand crank drill to create a counter sink on the inside of the barrel.
Using a gouge I dug a pit into some fireplace liner material, cut up my 14k gold, put it in the the recess and melted it into a lump. A firebrick could be used in a similar manner. I got this material about 15 years ago from a friend who used to sell gas fireplaces, thinking it would be useful for something.
I annealed the gold and forged it (pounded it) into a 16 sided cylinder shape, then hammered (extruded) it through a series of holes, each a drill size smaller than the previous one. After about 3 holes I stopped this process because I didn't like the way things were going.... probably because at this point I was still struggling with properly annealing the 14k gold.
So I decided to build a better mouse trap. I originally avoided trying to cast the plug because I have no crucible or casting sand. Then I thought maybe I could use the material at hand, and some gravity to do the casting work for me. So I drilled a 3/16" hole in my fireplace liner about 3/8" deep. ( I had to use a slightly smaller drill to get my hole to come out the proper size). Then I scooped another, shallower trench next to my hole, then used a v-parting tool to connect the trench and the hole. Here's a couple of pics to give perspective to the description:
I raised one end of the liner material with a scrap of 4x4, and placed a metal lid under the bottom end in case my gold made a run for it. I coated the gold with some homemade flux - approx. 95% borax, 5% washing soda and slog of methyl alcohol to make a slurry paste.
VIOLA! I love it when a plan actually works! The hole filled up and the remainder of the molten gold ran about halfway down the ramp before it froze into a lump. Now I had a plug I could work with. The plug was then annealed.
I drilled a 1/16" hole through the a block of steel, then a 3/16" hole in the steel a bit shorter than my plug (centered on the smaller hole), reamed it almost flat on the bottom, and used the same cutter that was used inside the barrel to cut a countersink. The gold plug was then inserted and beat on with a hammer and then a punch until it filled the countersink.
You can see what the 1/16th" hole was for.
The plug was quite stuck in the hole!
I made an angled punch to fit inside the barrel. The leg that fit in the barrel was drilled and tapped to accept 8-32 screws. I filed the heads of a couple different screws to different dome shapes to force the plug to completely fill my internal countersink. I moved it around the base of the plug, and varied the angle of the tool as I went, hammering until I was satisfied with the results.
I took a gate hinge from my scrap box and cut a somewhat less than half round section, drilled a clearance hole and placed a cut off bolt with a nut and washer in it to create a jack-stand that fit inside the barrel for support of the gold rivet. I filed a rounded point on top of the bolt.
I crudely ground an old cheap wrench so it would fit inside the barrel, inserted the jack-stand, and screwed it up tightly against the bottom of the rivet. I forgot to snap a photo of the jack in the barrel...
Using various ball peen hammers, and also variety of flat and round faced punches, I hammered the gold until i filled the outside countersink. I checked the jack-stand frequently and tightened whenever the nut would turn some.
Then I clamped the top of the plug in place and gave it a few more whacks on the inside to insure a tight fit everywhere.
When satisfied, I ground a plug tap and ran it in to the shoulder to make sure my breech plug would fit back properly.
The outside of the rivet was filed flush with the barrel flat, then center was marked and punched:
A 1/16th" hole was then drilled through the center of the rivet. Another coning tool was made using a 5/32" round file, inserted from the inside and an internal cone was cut in the rivet - carefully so as to not cut into the flange.
And it was finally finished! Yippee! That darn near flat wore me out.
Thanks for looking,
Curtis.