How Deep Can I Go

[Frizzen]

Need some advice. Got a 13/16 Rayl .32 cal pistol barrel. Need to drill and tap two holes 10-32
about two inches apart to hold the barrel onto the stock. How deep can I make the holes? The
bore dia. is .320  and the groove dia. is .340.

[D. Taylor Sapergia]

Phil, you can safely drill 1/8" into the barrel, assuming the bore is in the middle of the tube.  Here's how it works...13/16" is .8125".  The groove diameter is .340" so subtract it from the major dimension = .4725".  that makes 1/2 of that all around the bore, or .4725 divided by 2 = a wall thickness of .23625".  If you sink the drill 1/8" into the barrel, you'll have .236 - .125 = .111 or a little over a tenth of an inch of steel.  But measure the barrel across the flats to be sure you have an even 13/16" to deal with.  If less, take that into consideration.

[Jim Kibler]

In order to get as many threads as possible, you can cut flat bottomed holes.  Drill the holes to the desired depth with a standard drill and finish up with a flat bottomed drill.  You can make a flat bottomed drill by carefully regrinding a standard drill.  Start to thread the holes with a tap that has a bit of lead to it.  Finish it up with a bottoming tap.  I use a standard tap that I just cut back for a full bottoming tap.  This is how I've done lock plates with blind holes and it has worked pretty well.

[Acer Saccharum]

You can also dovetail a boss onto the bottom of the barrel, and run your threads into that.

Make a tall wide boss so you can run the loading rod thru it, and the section of boss above the rod can be tapped and threaded for the holding screw.