Another Parting off Thread

I guess I'm confused with terminology, I was thinking the blade and the part had to be exactly parallel on the face, as in no tangents. to cut straight. That would make them perpendicular.
 
Until now I've had trouble parting (100 year old lathe!) and mostly just used the bandsaw. Saw this vid, which was referenced above and ordered the tool and some inserts. Made a adjustable support plate (surface ground) that rests on the bed and an adjustable rod that slides along it that supports the tool at the clamping point. Works great and I'll be parting off in the lathe from now on!
Thanks for your interest
Aaron

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Aukai said:
I guess I'm confused with terminology, I was thinking the blade and the part had to be exactly parallel on the face, as in no tangents. to cut straight. That would make them perpendicular.
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Okay, the blade has to be perpendicular to the rotational axis, You're saying that you are setting the blade parallel to the work face. That's okay, as long as the work face is flat (it's not always - what if you had just turned a radius?). What I do is set the angle by sighting down the edge of the parting blade and aligning it with the front of the carriage. The blade I use (cheap Chinese HSS 0.0625" P1 blank) has enough flexibility that small perpendicularity errors are not a problem (it just cuts a slight radius in the work).
 
I did some parting-like operations today on my power feed project. I had to cut a groove .200" wide by .200" deep in a piece of 3 1/4" 12L14. I resisted my urge to be gentle and turned it in a lot faster than I wanted to and it cut pretty good. Still had some chatter but nothing as bad as the past. I think that it is just a matter of me gaining enough confidence to feed it in fast enough. Every time I feel a little more confidence and it goes a little better. I'll keep posting as I do more.
 
It's pretty much all in the setup, sometimes if I hear or feel something not right, I'll double check. Thanks for posting it up, bigger diameters, I play with RPM too.
 
Just a follow up for everyone who offered me some guidance: I think I found the issue, I noticed the parting tool would almost swivel when it was mounted in the tool holder. I checked the bottom of the tool holder (where the tool mounts in the holder) against a straight edge and realized it was bowed (crowned) in the middle. I took my finest diamond sharpening stone (flattest surface I have) to the crown and it seems much flatter. I have since done 5 or 6 parting operations with almost no chatter while running in back-gear, It still wants to chatter at normal speeds, but now I am confident enough to part instead of sawing it off.

THANKS TO ALL WHO HELPED WITH THIS!
 
walterwoj said:
Just a follow up for everyone who offered me some guidance: I think I found the issue, I noticed the parting tool would almost swivel when it was mounted in the tool holder. I checked the bottom of the tool holder (where the tool mounts in the holder) against a straight edge and realized it was bowed (crowned) in the middle. I took my finest diamond sharpening stone (flattest surface I have) to the crown and it seems much flatter. I have since done 5 or 6 parting operations with almost no chatter while running in back-gear, It still wants to chatter at normal speeds, but now I am confident enough to part instead of sawing it off.

THANKS TO ALL WHO HELPED WITH THIS!
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I have been having fantastic luck parting at 36 RPM spindle speed.
 
I did my 2nd part today with 4130 on the new lathe, the first one with a P2 blade was a little concave. The 2nd one I used the 1/8" Iscar at 90 RPM, on slow feed it started complaining, I hand fed it, and increased the feed, it started curling. Changed the feed rate on the Norton box and it sliced right through.
 
Aukai said:
I did my 2nd part today with 4130 on the new lathe, the first one with a P2 blade was a little concave. The 2nd one I used the 1/8" Iscar at 90 RPM, on slow feed it started complaining, I hand fed it, and increased the feed, it started curling. Changed the feed rate on the Norton box and it sliced right through.
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You have more courage than me if you are using the power feed for parting.
 
Try it, you'll like it. Keep up with cutting fluid. It works, you have the rigidity, make it square, and on center. 36 is a little slow, depending on diameter, you've been doing some big stuff.
 
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