Hi,
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This is from my early days when I 1st started out working in a shop:
FREEHAND and on a 1920 Hendey.
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You need to have your tool holder short as possible and a solid setup.
I always ground the under relief to the curve of the grinding wheel.
Flat on top. Perpendicular to the work and dead on centerline. Run
slow, not too fast. LOTS OF SULPHUR BASED OIL. I ease in to the
work, then I add a lot of handwheel pressure torque. Doing it freehand
it is a touchy-feely thing. Not too easy / not too heavy, but heavier
than you would think, steady, even pressure. Of course your machine's
ways/gibs need to be no slop there.
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Now with NC tape or CNC, you can keep your surface feed rate constant as
the diameter is reduced, you can increase your speed. And if an
enclosed housing, you can run coolant as liberally as you wish to flush
away the chips and keep everything cool. And CNC tooling tends to be a
very solid setup.
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The other thing to consider is use a good piece of tool bit tool
steel---USA, sorry. The import stuff is crap. Carbide insert tooling
and the appropriate holder will do better results but more $$.
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One old fart told me to not let my chips get hotter than corn yellow as
to how to judge your speed. I realize serious production requires
powder blue chips, but if doing it freehand, that's another story.
-
-+-
Kurt

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Trouble with cut-off operation on lathe

Group: rec.crafts.metalworking Date: Sat, May 13, 2006, 7:58pm From:
(Jim*Reed)
This is my first lathe and I am having trouble with using a cut-off
tool. I usually am cutting of mild steel, although I've tried stainless,
brass, and some junkyard shafts. The diameter ranges from 6" to 1". On
almost every cut I have the cut-off tool popping at times and chattering
at other times. All of my cuts look as though I used a machete and
chopping motions while the lathe rotated.
I have made sure the tool is 90 degrees to the work, that the tool meets
the work at or just below even with the center, and that everything is
tight. I have broken a few cutoff tools, and once hit the wall over 20
feet away with the broken piece. (Yes, I wear safety glasses). I am
using a tool by Wholesale Tool (wttool.com), page 156 of their latest
catalogue. It is a "P-Shaped M-2 cut off blade". Specifically, the P4 -
5/32X11/16X5. I flood the cutting area with oil. I have tried almost
every speed on the lathe - roughly 150 to 450 RPM. My lathe is a
Reed-Prentice 16X54, and the toolholder is an oriental Alorix knock-off.
* I've used a new 15" four jaw and a 8" three jaw chuck.
What do I check/change?