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LEAVE THEM HANGING,parting on the lathe

edwin dirnbeck

Hot Rolled
Joined
Oct 24, 2013
Location
st,louis mo
Since 1976 ,I have made thousands of DIFFERENT parts on NC lathes in tool and die shops.Most parts are nasty tool steel,prehard 4140,h13 d2 ect.Not production quantities ,usually 1 to 10 parts.. I found that damage to the parting tool usually happens when the part comes free and the part goes flying.SOO,I allways program the parting tool to rapid retract when it reaches .150 diameter.The lathe stops and the part is left hanging. I can wiggle the part back and forth and it breaks off.For long parts ,I increase the diameter. If I miscalculate and the part wont break off easily, a few strokes with a good hacksaw ,weekens the nub and the part break off. OH YEA,this also keeps the part from getting banged up when it goes flying.This also works when faceing.The hardest thing on carbide is cutting on center. You have almost zero surface feet per minute and you are bulldozing the nub at center.If you leave the nub,you can easily remove it and make a beautiful part with a 2 inch air sander with the spindle turning about 300 rpm. Of course this means reaching in and running the spindle with the door open. Edwin Dirnbeck
 
I don't understand the purpose of this thread. Are you answering someone's question or are you just giving a QOL tip?
 
That procedure also works good on very small plastic parts that will get lost in the chips if fully parted. With the small PEEK parts that we call mouse droppings stopping about .015 shy of cutting off works, break the part off and press cycle start again to finish cutting off the nub. Cycle repeat will take it past the M02 cycle stop so in practice the lathe only stops once.
 
I don't understand the purpose of this thread. Are you answering someone's question or are you just giving a QOL tip?
Well it is definitely not a qol tip,because ,I don't know what that is.This is A lathe procedure that has worked for me.I think others might not know this,and it would be helpful.Edwin Dirnbeck
 
I have always done this running manual machines also. Wouldn't help much for lights-out though. For that maybe you could add a tool holder with a spring loaded hacksaw blade and program it to cut the part off with back and forth strokes? :D
 
I do the same thing, but use a stubby flat screwdriver in the gap to pop them off, my parts don't weigh that much.
 
Kinda puts an end to "lights out un-attended operation" that CNC machine is for eh ?....:crazy:

Or just doo like been done for 50 years on automatics, place the cut off
tool on top.....:nutter:
 
If you leave the nub,you can easily remove it and make a beautiful part with a 2 inch air sander with the spindle turning about 300 rpm. Of course this means reaching in and running the spindle with the door open. Edwin Dirnbeck


Won't catch me or any of my employees using an abrasive tool inside a lathe enclosure....Lathe way wipers not designed to exclude fine grit....Good way to kill a machine.
Cheers Ross
 
Won't catch me or any of my employees using an abrasive tool inside a lathe enclosure....Lathe way wipers not designed to exclude fine grit....Good way to kill a machine.
Cheers Ross
Could do what I do, pause the machine break the part off and press cycle start to restart the spindle and finish cutting off or bring another tool up and face it off.
 
Kinda puts an end to "lights out un-attended operation" that CNC machine is for eh ?....:crazy:

Or just doo like been done for 50 years on automatics, place the cut off
tool on top.....:nutter:
As I stated in my OP ,mostly 1 or 2 parts for tooling. No such thing as lights out production. We use the NC to routinely generate complex shapes thst use to be very tedious. Also ,when parting off tough tool steel,it doesn't matter if the tool is on top ,bottom or in between,the part pops off and the last bit of nub destroys your insert. Edwin Dirnbeck
 
As I stated in my OP ,mostly 1 or 2 parts for tooling. No such thing as lights out production. We use the NC to routinely generate complex shapes thst use to be very tedious. Also ,when parting off tough tool steel,it doesn't matter if the tool is on top ,bottom or in between,the part pops off and the last bit of nub destroys your insert. Edwin Dirnbeck

The last bit of nub destroys your tool ?

I'm sorry to hear that.
 
Or you could just make sure the tool is dead on center and just part the parts off and let them drop in the parts catcher. It is not rocket science.
So a 4 inch diameter piece of h13 5 inches long spinning at 2000 rpm ,is just going drop in the part catcher? Yes I part off 4 inch h13 routinely. I work in a tool and die shop and make 1 to ten parts. Never had time to set up and use a parts catcher.Cnc machines are not just for production. Edwin Dirnbeck
 
Agree with a good tip. Perhaps an/the op could start a title with QT: quick tip.

good title "lathe parting QT" .

Most/much of the stuff I write about grinding is for the new guy and apprentice...no need to beat up a guy because seasoned guys already know something.
 
I have never liked the sound of a parted off piece clinking off my ways. I mostly eyeball the parting tool on center which invariably leaves a tit. I can generally just bend it back and forth and it comes right off. The problem I usually run into is that now I have a piece left in the chuck with a tit on it. If I have to center drill that piece for the next operation then I have to deal with the tit somehow. I keep an end cutting mill bit in a morse taper holder that makes quick work of the tit. The center drill then has a nice clean surface to start from.
 
So a 4 inch diameter piece of h13 5 inches long spinning at 2000 rpm ,is just going drop in the part catcher? Yes I part off 4 inch h13 routinely. I work in a tool and die shop and make 1 to ten parts. Never had time to set up and use a parts catcher.Cnc machines are not just for production. Edwin Dirnbeck

So what, I part 4" as well. Use your rotating chuck in the tailstock to hold the work. As I said tool on dead center = no nub to wreck your tool. It still is not rocket science.
 








 
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