New lathe trouble

If I go to a higher feed rate then it is “threading” or skipping. Still not smooth.
 
Nice chuck, two part jaws so you can make your own soft jaws...love it!

The work piece looks like just under an inch.....is that right?
Is that cold rolled or stainless?

If cold rolled, for HSS tool and for cold-rolled I'd want to be about 80 sfpm, so that means around 300 rpm for a starting point.
I would then adjust up/down to see what works better.

However since you are already in that ballpark, I think you should concentrate on the cutting tip.
I see you are using HSS insert tooling. I have no experience with that, but now grind my own.

There is a ton of info here:
https://www.hobby-machinist.com/threads/models-for-grinding-hss-lathe-tools.62111/post-511692
(get a coffee, it is a very long thread, but worthwhile, I promise!)

One take-away should be the benefit of a nose radius on the tool.
What inserts do you use and what is their nose radius?

It might be just the picture, but it almost looks like a little tip damage or built-up edge on the cutting tool:
1588800492704.png

ScreenShot055.jpg

Please have a look with good light and magnification.

Endeavor1 said:
I have seen someone with a very similar machine get a mirror like finish. I’m not sure if my expectations are to high or not.
Click to expand...

Stick with us, you will get there!

-brino
 

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It’s Stainless. That pc is just under an inch. How can I tell when the RPM’s are to high? I went up to 700 RPM’s. The cut there was the best I’ve had. These are HSS inserts. There is a little build up on there. I’ll sharpen and try again. I’m out of town until next week now.
 
416 is a free machining SS. What the max RPM you've tried?
Forget it, I see 700
 
Endeavor1 said:
I’m using high speed steel insert tooling. This was cut at a speed of 250 RPM, it’s about the best finish that I can get.View attachment 323437
Click to expand...

My guess is the gibs (and don't forget the compound slide gibs, too) are not tight enough.
Ideally, only one gib is allowing motion while the rest are locked down. In practice 2 axis are in use, but the 3rd should be locked.
Also not compound slide position (when not using compound) is where the slide and end of the compound are aligned. This allows the forces of cutting to articulate best into the cross slide.

With a similar lathe, I found there is just enough gib friction to notice it on the wheels (with your hands) but not enough where it could be rattled by hand.
Also note:: lube it often and well, ways are supposed to almost drip oil in use.
 
You can try a vertical shear tool, as it cuts with a shearing action it can give a good finish. Once the tool bit is ground I hone it on an oil stone. You can on!y take a light finish cut with a vertical shear tool .001 maybe .002. I normally feed in with the compound so as not to over feed the tool.
 
This is going to sound dumb but are you sure the tip of the tool is on center height?

Also, what does your lead angle on the tool look like when you're cutting? Can you post a pic so we can see the tool from overhead when it is cutting?
 
gearhead lathes often have a nasty propensity of transmitting gear noise into the part they are turning.
no so bad for roughing work, but for finish work...
any vibration, coupled with an overly sharp tool may very well create a vinyl record like appearance on your parts :mad:

try a rounded tool, or a generous radius

my favorite HSS grind is right here...
it allows a very small 90watt unimat to eat 304 like cake.
(8° rakes all around- for simplicity)

the tool may improve your finish
 
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