New lathe trouble

i cut a lot of stainless on my Grizzly 4003G, the 2" stock i start with is often spinning at 800 RPM, cutting .030 - .040 with a medium feed rate and comes out beautiful.. as i get smaller i spool it up to 1000 rom. using carbide insert tooling.

I've recently been cutting 2.25" CRS with the same carbide, spinning it as fast as my lathe will go, 1400, coming out like a work of art at .030, again medium feed rate (not sure what that number is) but big, hearty chips flying.. i often where a full face shield when doing those cuts...

As said before: speed may need to be faster, DOC a little deeper .. and remember.. "a little cardio never hurt anybody"
 
All of the above plus........

With the lathe turned OFF, if you grab the tool post can you move it with a little back and forth push-pull?
What about side to side?
What about up and down?
What about twisting it?

Any play in the tool post (from the slides, the lead screws, the tool post bolt, etc.) can lead to chatter and horrible finish.
If you see any one of these investigate.
It could be as simple as the jibs not tight enough, or the t-nut under the compound being too thick, etc.

Stay with us and give as much info as you can.
There are a lot of very smart and talented folks here that will get this solved!

-brino
 
I have a 12x36 and rough steel at .050 DOC (diameter) and usually .008"/rev or somewhere around there. I use all indexable carbide but HSS is perfectly acceptable. I can also fine finish at .001 DOC without chatter.

Tips:
  1. Use well supported stock, avoid stickout over 3:1
  2. Make sure tool is on or slightly below centerline
  3. Minimize tool nose radius
  4. Use tailstock when possible
  5. Stainless makes stringy chips, pick tool accordingly
  6. Use inserts and tools with sharp edges for fine finishing
 
My 1440gt had loose gibs everywhere, which gave bad finishes, until I realized the problem.
 
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.FB98DC93-835E-441D-A773-6EDDDF3F50B1.jpeg
 
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. The other person was using a 3 phase machine.
 
Photo from tail stock perspective of tool in cut.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
Most likely need a higher feed rate, too slow will just rub, tearing and chatter. What kind of cutter/insert are you using. As others noted check the gibbs, lock the cross slide and see if that helps. Other factors could be tool cutter height and parallel to the chuck.
 
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