[modeleng] Re: coarse threads

 Previously, I mis-spoke about using it for cutting
 grooves in rifle barrels.  This machine would not do
 it, but now the question arises, in my mind, at least,
is HOW are the correctly pitched groves, say one turn
 in twelve inches, cut in the guides that control the
 cutters that actually do the work?  Old timers carved
 them into a cylinder of wood with chisels, following a
 spirally wound string, but how now??

Al Messer


Al,

Rifle barrels are cut with-- - hold onto your hat- - - a rifling machine!!! 
But instead of a spiral twisted guide, there is a heavy cast iron beam that 
sits above the ways of the rifling machine.  As the cutter is pulled back 
and forth, a shoe rides (like a taper attachment, sorta) along the bottom of 
the beam which is at a slight angle to the carriage ways.  This causes the 
rifling head to rotate through some gearing and the bar itself has an 
adjustment that allows changing the angle to make different pitch rifling. 
Simple when you know how it is done.  I have a few photos of the rifling 
machines at Springfield around 1900 and they all have this heavy beam 
suspended above the carriage ways.  The book also shows the original 
Blanchard stock making lathe which originated by Mr. Blanchard at 
Springfield armoury about the time of the Civil War.  FWIW, The  key cutting 
machine at your local hardware or Wally World is a sort of primitive 
Blanchard lathe only the work is not revolving.

Jesse the Redneck in W. Tennessee


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