Bill,
Gun drills are similar to lathes except the tailstock is made specially to hold
extra long drills. They also have coolant for the bit. The bit has a
guide-support at the end closest to the rod to be drilled. The drill has one
straight long flute and is stationary. As the rod is turned in the tailstock,
the drill is advanced by the tailstock which is geared to the lathe. It
advances slowely and takes about 45 minutes to drill a rifle barrell. After
drilling, the barrell is reamed, then rifled, and chambered.
For the brass insert, you can get a piece of brass tubing with an OD of 3/8".
If the ID is a little larger than 1/4" not to worry, but not a whole lot
different, say 0.010" at the most. After you cut the tubing off for the length
you need, you then split one side down the middle opening it up like making a
C. When the set screws are tightened against it, it will compress around the
1/4" shaft due to the split and hold it in place. You can make this with a
small hacksaw or coping saw. Just make sure the gap in the split is wide enough
so it will compress to 1/4" ID.
Best,
Will
*********** REPLY SEPARATOR ***********
On 12/23/05 at 8:00 AM Bill Turner wrote:
>ORIGINAL MESSAGE:
>
>At 03:03 AM 12/23/2005, W0UN -- John Brosnahan wrote:
><snip>
>>finding some 3/8 brass rod and drilling a 1/4 inch hole in it -- plus
>>clearance holes
>>for the set screws. Easier on a lathe, but with care a drill press
>>will do it.
><snip>
>
>
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>This brings up a question for you machinists out there.
>
>I once watched a program on the Discovery Channel which showed how
>rifle barrels are made. It said in order to drill a perfectly
>centered hole in a rod, you clamp the drill bit stationary and rotate
>the rod as if it were the drill bit. Done this way, the rod will
>automatically center itself around the drill bit.
>
>Is this true or just an old (machinist's) wives's tale?
>
>73, Bill W6WRT
>
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