On Tue, 08 Apr 2008 09:21:20 -0400, Joseph Gwinn
wrote:
In article ,
Gunner Asch wrote:
On Mon, 07 Apr 2008 22:10:04 -0400, Joseph Gwinn
wrote:
In article ,
Clark Magnuson wrote:
I have a 5914 that shakes hard with a cut off blade.
I am tense, and when the shaking causes something to fall over in the
pan of the lathe, I just about jump out of my skin.
I burned those nerves out long ago.
The cutoff has made sharp bang noises, to the point I thought something
must have broken, but no damage ever found. I think it was passing a
lump of chips, apparently because the tool was cutting on the side
because the toolpost had rotated.
The banging noises come from the workpiece loading up, jamming in the
work, then coming free again. Push harder, or a smidge less.
That was my guess. The sidewalls of the groove are ragged and galled,
which is a clue.
How much side relief are you grinding in? Should be just a couple
degrees, but you DO need side relief
Need to find the optimum degree of push.
Sometimes spinning faster helps. I part off at about 600- 800 rpm on
stuff under 1"
Proper
tool nose geometry is essential. Grind it in a pickle fork
configuration, with a chip breaker in the middle.
Going in with a flat bladed "chisel" on a smallish lathe is
problematic.
The top of the T is scooped, but gently. The blade is 1/8" wide by
11/16" deep. I'll have to try putting a narrow groove in the center,
using a Dremel tool. Need to make sure the center can still cut,
though, as there would otherwise be no place for the resulting disk to
go.
Some of the carbide inserts used for cutting off also have this
geometry. I recall that the Manchester ones do, from the photos in the
J&L catalog.
I also had it stall the workpiece in the 3-jaw chuck, which did not
stop. Very dramatic. I backed off, then resumed cutting off. The
workpiece now wobbled a bit, but the cutoff succeeded without further
drama. I must have pushed too hard, but I'm getting the feel.
Check center height. You must be DEAD NUTs and on center.
It was right on. Think it still is. Will check, though this has not
tended to drift.
I buy used tool bits cheap, precisely so I don't need to cry when I
break something. My objective is to not break the lathe, but all else
is open season.
I now hack saw off pieces and then face it with the lathe.
But I'm stubborn, and am using cutoffs as a way to uncover accumulated
problems, so they can be fixed. If the lathe can part off, everything
else will work.
This is an industrial lathe, and would have been laughed off the planet
if it were unable to part off. So if it cannot now do cutoffs,
something is wrong and ought to be fixed.
Joe Gwinn
http://yarchive.net/metal/parting_off.html
From Robert Bastow.
I'll read it.
Joe Gwinn
"[L]iberals are afraid to state what they truly believe in, for to do so
would result in even less votes than they currently receive. Their
methodology is to lie about their real agenda in the hopes of regaining
power, at which point they will do whatever they damn well please. The
problem is they have concealed and obfuscated for so long that, as a group,
they themselves are no longer sure of their goals. They are a collection of
wild-eyed splinter groups, all holding a grab-bag of dreams and wishes. Some
want a Socialist, secular-humanist state, others the repeal of the Second
Amendment. Some want same sex/different species marriage, others want voting
rights for trees, fish, coal and bugs. Some want cradle to grave care and
complete subservience to the government nanny state, others want a culture
that walks in lockstep and speaks only with intonations of political
correctness. I view the American liberals in much the same way I view the
competing factions of Islamic
fundamentalists. The latter hate each other to the core, and only join
forces to attack the US or Israel. The former hate themselves to the core,
and only join forces to attack George Bush and conservatives." --Ron Marr