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PM-1660TL
- Thread starter erikmannie
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I try to stay out of discussion where carbide inserts are used but can't resist this one. There are all kinds of "cold rolled steels" so I'm not sure what the cutting speed is but I suspect it will be near 800SFM for that piece. If so, recommended RPM would be somewhere near 1500 rpm and I would try it.
As Mark said above, you need to pay attention to the nose radius as this influences the minimum depth of cut and your feed rate. I suggest trying a depth of cut about 0.010" deeper than the nose radius; this will stabilize the tool, minimize radial deflection and give you a consistent reduction in diameter. I would also boost feed rate to give the chip breaker a chance to work. Most of those spiral lines you're seeing is due to too low a feed rate and I suggest you try a feed rate of between 0.5 - 0.75 the nose radius and see what happens.
The last thing I would suggest is that you turn the tool about 5 degrees towards the chuck and see how that impacts the cut. This should reduce cutting forces a bit and hopefully aid in better finishes by bringing more of the end cutting edge into contact with the work.
As Mark said above, you need to pay attention to the nose radius as this influences the minimum depth of cut and your feed rate. I suggest trying a depth of cut about 0.010" deeper than the nose radius; this will stabilize the tool, minimize radial deflection and give you a consistent reduction in diameter. I would also boost feed rate to give the chip breaker a chance to work. Most of those spiral lines you're seeing is due to too low a feed rate and I suggest you try a feed rate of between 0.5 - 0.75 the nose radius and see what happens.
The last thing I would suggest is that you turn the tool about 5 degrees towards the chuck and see how that impacts the cut. This should reduce cutting forces a bit and hopefully aid in better finishes by bringing more of the end cutting edge into contact with the work.
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You have a beast it won't complain, use it like it was meant to be used. Tool point toward the chuck(lay back) less DOC for fine finish, your in big boy territory for carbide RPM & HP, use it. I'll be corrected if I'm wrong. 
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I got another day off (resting my back), so the fun continues. I received the circuit breaker mounts so my Dad & I will install the 30A components, and then I need to make sure the 1660 is completely level.
When I tried to turn between centers on the 1660, I put a dead center in the MT6 to MT4 reducing sleeve in the chuck. The dead center did not run true. I think it had something to do with the weight of the reducing sleeve (i.e.the reducing sleeve wasn’t in there straight ). I’m going to be taking another look at that today. Hopefully my lathe bar whip incident didn’t crack or bend my spindle.
I am going to see about that with the Noga arm right now.
When I tried to turn between centers on the 1660, I put a dead center in the MT6 to MT4 reducing sleeve in the chuck. The dead center did not run true. I think it had something to do with the weight of the reducing sleeve (i.e.the reducing sleeve wasn’t in there straight ). I’m going to be taking another look at that today. Hopefully my lathe bar whip incident didn’t crack or bend my spindle.
I am going to see about that with the Noga arm right now.
Yea I agree that you are going too light. I hate mold steel but for most carbide inserts to work well and leave good finishes you are gonna need to pump up that rpm and .002” per rev is ok for finishing but a bit light for anything else. A cnmg 432 insert you can push to .2 off the radius and .01-.02” per rev.
This was 5.5” stock and the part was around 4”
Outside was spun at around 900 rpm. So that’s about 900sfm. .1per side .009” per rev but that was with a smaller dnmg332 insert. A cnmg could have went much faster but the part also had a very long stickout.
I know that’s on a cnc. But your lathe is solid and can probably do the same.
With carbide inserts unless you get ground inserts that are specifically ground sharp the inserts come pretty dull intentionally as they are designed to take cuts like above.
As a general rule
Carbide inserts do not like to take a depth of cut less than their nose radius.
Her is some videos for you not very high quality but just shows you the same cut on the manual vs cnc. I was spinning slower on the manual but that was a interrupted cut.
This was 5.5” stock and the part was around 4”
Outside was spun at around 900 rpm. So that’s about 900sfm. .1per side .009” per rev but that was with a smaller dnmg332 insert. A cnmg could have went much faster but the part also had a very long stickout.
I know that’s on a cnc. But your lathe is solid and can probably do the same.
With carbide inserts unless you get ground inserts that are specifically ground sharp the inserts come pretty dull intentionally as they are designed to take cuts like above.
As a general rule
Carbide inserts do not like to take a depth of cut less than their nose radius.
Her is some videos for you not very high quality but just shows you the same cut on the manual vs cnc. I was spinning slower on the manual but that was a interrupted cut.
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It took me just under 2 hours to install a 30A circuit breaker & receptacle in the American Rotary AMP-10. My Dad was an electrician, and he watched and advised.
I used 8 AWG wire. American Rotary used 10 AWG wire for the 20A circuit.
Everything went smoothly, and it tested OK. Now the 1800 RPM spindle speed doesn’t pop my breaker, as it did with the 20A breaker.
Also put on a longer (SO) cable, so now I have my rotary phase converter farther from the garage door and out of the weather. This allowed me to reunite my tool chests.
I used 8 AWG wire. American Rotary used 10 AWG wire for the 20A circuit.
Everything went smoothly, and it tested OK. Now the 1800 RPM spindle speed doesn’t pop my breaker, as it did with the 20A breaker.
Also put on a longer (SO) cable, so now I have my rotary phase converter farther from the garage door and out of the weather. This allowed me to reunite my tool chests.
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I was turning between centers today. The DRO (mounted on an arm) was vibrating at 900 RPM, but not at 620 RPM.
Even at 620 RPM, the lathe was throwing a few chips all the way across the garage (i.e. the length of a car).
This steel round bar is 18” long with a diameter of about 1.7”.
I am so happy with this lathe, but I have to bolster my courage & work up to the high RPMs & deep cuts that carbide calls for.
Even at 620 RPM, the lathe was throwing a few chips all the way across the garage (i.e. the length of a car).
This steel round bar is 18” long with a diameter of about 1.7”.
I am so happy with this lathe, but I have to bolster my courage & work up to the high RPMs & deep cuts that carbide calls for.
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