In article ,
Gunner wrote:
On 13 Apr 2005 12:26:48 -0700, wrote:
[ ... ]
My current challenge is that the majority of cuts I take are not
entirely smoothe, but feel threaded. I believe that this is due to the
[ ... ]
If the shaft feels "threaded", there are some possibilities.
#1, feed rate is much too fast, or spindle is turning much too slow
and you are actually threading.
In particular, most lathes with a quick-change gearbox (not sure
about yours) have two forms of longitudinal feed available:
A) The usual, using the leadscrew as is used for threading,
engaged by closing the half-nuts.
B) "Power feed" -- the leadscrew also has a keyway cut down its
length, which turns a worm gear inside the apron. This gear
either turns the handwheel on the carriage for a particularly
fine longitudinal feed, or turns the crank for a smooth
cross-feed. (This is determined by the position of some form of
lever.)
If you have this, it should be used in preference to the
halfnuts to minimize wear on the threads of the leadscrew.
Also, the feed from the power feed is noticeably finer than that
produced by the half nuts, which are truly designed only for
threading.
The feed rate changes with the selected thread pitch, but in all
cases, the feed is finer than the thread pitch. As examples,
I'll give the coarsest and finest settings on my Clausing
quick-change box:
TPI Lead Long Cross
feed feed
-------------------------------------------------
4 0.125" 0.0367" 0.00017"
224 0.00446" 0.00065" 0.00016"
As you can see, at all settings, the power feed gives much finer
feed than the threading half nuts. (By a factor of about 3.4:1
on this machine.)
All of Gunner's other advice is good, too -- I just thought that
as a new lathe owner, you might have missed the longitudinal feed (if it
is present on your Atlas -- it is not on my tiny 6x18, which really does
not get used these days.
Good Luck,
DoN.
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