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Barrel
Making article index
CHATTER WHILE CHAMBERING
The 14x40 Nardini lathe is an excellent chambering lathe.
Here is Rob Horton polishing the chamber of one our 22 drop-in barrels.
The following is an answer I wrote to a customer that had experienced
chatter in a barrel while chambering it. I've included it here under our
barrel section as a help should you experience that problem. In this case
the customer had fired cases that had longitudinal flats on them.
Dear Sir:
What you've described is a classic example of a reamer chattering while
it cuts. And your gunsmith may well be right, it could be the result of
the reamer geometry. When reamers are made the flutes are not cut 60 degrees
from each other (in the case of a 6 flute reamer). Instead the flutes
are staggered a few degrees either side of 60, as per the table in the
Machinery's Handbook. This built-in stagger helps prevent chatter on a
long (for its diameter) reamer, like a chambering reamer. But sometimes
a reamer will still chatter, especially a new one that is very sharp and
cutting aggressively.
Once chatter starts it is very difficult to "get under" it.
Loading up the flutes with chips and making a heavy cut is the best method
I've found. After your reamer has cut a few chambers it will probably
get much better.
However that does not help your current situation. Running the reamer
in by hand, as you suggested, will most likely make the situation worse,
not better. Setting the barrel back might do it, but it might not too.
As I said, it is very hard to "get under" the chatter. Holding
the barrel by the shank in the lathe chuck jaws and then rigidly holding
the reamer in a chuck in the tail stock might do it.
It is also possible to see chatter develop if the barrel or reamer is
held too loosely while it is being chambered. For example if the chamber
end of the barrel is being held in a steady rest but the steady rest fingers
are not tight, chatter can start. Or some floating reamer holders can
be loose or sloppy and allow the reamer to float too much. Along that
same line of reasoning I chambered once on an import lathe that had "light"
bearings. The whole headstock/spindle assembly was a little loose and
allowed the barrel to chatter. Tightening the bearings helped but was
not the ultimate solution (using a different lathe was).
Also it is possible for a reamer pilot that is undersize by quite a bit
to have some effect on the chatter problem.
I have never seen a problem related to reamer chatter that was a result
of the steel we use. The only things I can think of that might cause chatter
(because of the steel) is impurities in the steel or possibly material
that is too hard. But if either was the case we would have noticed a problem
with the barrel while we were manufacturing it and it would not have made
an acceptable rifle barrel.
Chatter with a reamer is a difficult problem to master once it has started.
You might want to talk to the reamer manufacturer about the problem too.
He might have some other suggestions.
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