Chips not breaking

J

jonathan01

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Hey, I just got started turning on my lathe. It is a PM 13x40. I am making some parts out of annealed 17-4 ph SS. I am turning down a 0.5" rod to 0.422" and 0.308". I am running it at 460 rpms with hss, and sometimes I tryout a brazed cabide tool at 755rpm.

I am using 3/8" hss blanks at 460rpm right now, and I am getting a pretty good finish at the slowest feed my lathe has. The only thing is I am getting long chips, they are coil shaped, but they get 10 to 20 feet sometimes. I am taking light cuts right now, because I don't have my coolant running yet, so the long chips break before they can warp around the work.

Thanks for any help yall can give me.
 
Many HSS bit configurations do not lend themselves well to chip breaking. Of all the standard HSS styles I regularly use, almost all produce stringy/springy swarf. You can try repositioning the tool or making slight tweaks in the grind and see if that helps. If you could post a picture of your bit, we can tell you if you stand a chance of controlling swarf with it.

I have much better luck controling chips with carbide because most inserts have dedicated chip-breaking grooves. Even still, there's no guarantee it works at all times.


Ray
 
You can always grind a chipbreaker in your bit. A groove parallel with the cutting edge works well for steels and such and I use a small half moon shape cut on the tip of the tool for really gummy/flexible materials like aluminum.
 
By any chance do you have pictures or instructions on how to grind such a groove in HSS? I've been able to make various shapes that seem to help but, a groove with decided improvement has eluded me.

Ray



Halligan142 said:
You can always grind a chipbreaker in your bit. A groove parallel with the cutting edge works well for steels and such and I use a small half moon shape cut on the tip of the tool for really gummy/flexible materials like aluminum.
Click to expand...
 
Stainless tends to do that unless you grind a chip breaker relief on the top of the tool bit.
Smoother finish can be had by honeing the point of your tool.
What is your DOC ? {depth of cut}
************Just Asking*************Gator**********
 
It seems as though all the tool angles play a part in the chip formation. I've had success cutting a shallow groove across the top face, perpendicular to the direction of cut, made with a narrow parting disk on a die grinder. I typically turn with HSS as my lathe is too slow for carbide, and most of my work is 1030 steel. I use large tool bits (even for small work) clamped directly in a four-way holder. My best chip breaker is a short section of .125 x 1/2 inch CR flat clamped in with the HSS tool, and extended to a point where it intercepts the chip and snaps it off.
 
Rtonder said:
It seems as though all the tool angles play a part in the chip formation. I've had success cutting a shallow groove across the top face, perpendicular to the direction of cut, made with a narrow parting disk on a die grinder. I typically turn with HSS as my lathe is too slow for carbide, and most of my work is 1030 steel. I use large tool bits (even for small work) clamped directly in a four-way holder. My best chip breaker is a short section of .125 x 1/2 inch CR flat clamped in with the HSS tool, and extended to a point where it intercepts the chip and snaps it off.
Click to expand...

That the same way I go about it, Though sometimes it depends on materials to how sucessfull it works. The clamp on chip breaker usually does the trick on stringy swarf.
 
Some times the best you can do is make a hook on a piece of heavy wire, put it in a handle and guide the coils away from you. Stainless is natorious for making long dangerous swarf. If nothing more you can interupt the cut on roughing cuts to keep the length of the curls down to a manageble lenth. But for the finish cut you may just have to use the hook and guide the swarf away from trouble. BE DOUBLE CAREFUL stainless swarf is as sharp as a razor blade, it will cut you or worse if your hand gets caught up in a ribbon of stainless the results can be horrible. And a loose end will be grabbed up and sucked into the lathe in an instant. What ever it takes do not let 20 foot long coils of swarf form.
 
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