Mid 1800s barrel boring drills

[rich pierce]

Yesterday several of us Vermonters visited the new owner of a mid-1800s rifling machine. This is from the Hilliard shop in Cornish, New Hampshire. The machine utilized a single spiral cut groove in steel tubes to give the twist. Twists from 1:26 to 1:72 or so were possible with the available guides, and 6, 7, or 8 grooves.

I’d seen most of the tools snd cutters and such before. However the twist drills used to bore barrels out were new to me. They were tapered twist drills with aggressive, forward-facing cutting edges. Take a look!

[bluenoser]

Interesting.  I presume the cutting occurs along the back edge and can see the rate of twist is about triple that of the modern twist drill, so would interpret that (perhaps incorrectly) as less aggressive.  If one were to remove the supporting web from a modern twist drill and reshape the gullet, would one not have about the same setup if taper and rate of twist were ignored?  I wonder if there is a reason they are all left-hand twist.
|Thanks for posting rich.

[James Wilson Everett]

Guys,

Barrel boring tool cutters were made with a left hand twist, but turned right hand.  This way the tool will directly follow an existing barrel bore and not wander off center.  The typical right hand twist cutters will wander off center quite easily.  Here is a photo of some of my 18th century style cutters that I use while boring barrels.



Here is a link to the 18th century style barrel boring tool.
https://americanlongrifles.org/forum/index.php?topic=42251.msg411430#msg411430

Jim

[Jim Kibler]

biggest reason for left hand twist and right hand operation is that otherwise the bit would just screw itself in the barrel.  Sort of like an easyout. 

Jim

[jmf]

How are these drills chucked up? If they are bore diameter, are they internally threaded on the back end to fit an extension?

[rich pierce]

How are these drills chucked up? If they are bore diameter, are they internally threaded on the back end to fit an extension?

They look from the picture like they are bored out at the back end to receive a long bar with a male portion that fits in and is then pinned.

[bluenoser]

Thanks for the explanation James.  Is it more of a scraping action than a shearing action?