# New lathe trouble



## Endeavor1 (Mar 14, 2020)

I’ve always had trouble getting a good finish. I just got a new lathe and hoped that the trouble would go away. I had an old grizzly that I inherited but just bought a PM 1440GT. I’m still getting slight chatter. I’ve tried new HSS inserts, Aurther R Warner. I’ve tried every speed and feed combo that I can.  Nothing seems to make it all go away. The best cut comes from manual feed as slow as I can. The slowest feed on the machine is .0028. I’ve tried carbide but that has been worse. The material that I’m working on is stainless and cold rolled steel. These are giving me about the same results.

thank you for


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## mmcmdl (Mar 14, 2020)

Tools like to cut , not rub . Not enough information here to make recomendations . Got pics of set-up and tooling ?

Roughing at .010 and finishing at .005 is a general starting point .


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## Ulma Doctor (Mar 14, 2020)

.0028" is plenty fine enough
have you tried tools with a nose radius or pointed tools?
what is your spindle speed?
some cold rolled steels look like crap no matter how you turn them
304 stainless will look like crap too if you don't have a deep enough doc, it is not friendly at all


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## MontanaLon (Mar 14, 2020)

Let er eat. Feeds and speeds are fine but depth of cut is important. I have had trouble taking light cuts in some material. Get just ok finish. But on my "roughing cuts" I get mirrorish finish. It will make you good at judging tool deflection and hitting your measurement with a bigger cut rather than sneaking up on it with 10 little cuts.

By chance did you move anything over from the old lathe to the new one, like the tool post?


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## Endeavor1 (Mar 14, 2020)

The stainless is 416 R. I’ve tried a crew different shaped tools. Nothing that was extremely pointed. Spindle speeds from 50-280 rpm. I’ve also tried several feed rates.
I’ve tried depth of cut from .001 to .050. The finish is slightly better with a shallow cut. 
The finish is very similar on both materials.


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## Endeavor1 (Mar 14, 2020)

The tool post is new tool holders are new. I’ve even tried new tools.


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## MontanaLon (Mar 15, 2020)

Endeavor1 said:


> The stainless is 416 R. I’ve tried a crew different shaped tools. Nothing that was extremely pointed. Spindle speeds from 50-280 rpm. I’ve also tried several feed rates.
> I’ve tried depth of cut from .001 to .050. The finish is slightly better with a shallow cut.
> The finish is very similar on both materials.


What diameter of work? Your speed seems low to me unless you are turning something pretty large.


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## darkzero (Mar 15, 2020)

As they say a pic (of your setup) is worth a thousand words. As the guys said, need more info.


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## aliva (Mar 16, 2020)

Sounds like your low on the speed side. Bump it up to at least 600rpm and try that, then star reducing. 
I turn mostly between 300-600 rpm, threading around 90-100, parting 200


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## rgray (Mar 16, 2020)

This goes all the way to what kinda floor it's on.


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## Driveslayer45 (Mar 18, 2020)

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"


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## brino (Mar 18, 2020)

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


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## macardoso (Mar 18, 2020)

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:

Use well supported stock, avoid stickout over 3:1
Make sure tool is on or slightly below centerline
Minimize tool nose radius
Use tailstock when possible
Stainless makes stringy chips, pick tool accordingly
Use inserts and tools with sharp edges for fine finishing


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## dpb (Mar 18, 2020)

My 1440gt had loose gibs everywhere, which gave bad finishes, until I realized the problem.


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## Endeavor1 (May 6, 2020)

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.


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## Endeavor1 (May 6, 2020)

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.


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## tq60 (May 6, 2020)

Photo from tail stock perspective of tool in cut.

Sent from my SAMSUNG-SM-G930A using Tapatalk


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## Suzuki4evr (May 6, 2020)

brino said:


> There are a lot of very smart and talented folks here that will get this solved!


What Brino said.


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## mksj (May 6, 2020)

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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## Endeavor1 (May 6, 2020)

Here is a view from the tailstock


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## Endeavor1 (May 6, 2020)

If I go to a higher feed rate then it is “threading” or skipping. Still not smooth.


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## Buffalo21 (May 6, 2020)

Higher rpm, lower feed rate


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## brino (May 6, 2020)

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:






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.



Stick with us, you will get there!

-brino


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## Endeavor1 (May 6, 2020)

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.


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## ddickey (May 6, 2020)

416 is a free machining SS. What the max RPM you've tried?
Forget it, I see 700


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## Mitch Alsup (May 6, 2020)

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.
> 
> 
> 
> ...



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.


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## derfatdutchman (May 6, 2020)

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.


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## mikey (May 6, 2020)

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?


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## Ulma Doctor (May 7, 2020)

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 

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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## ChrisAttebery (May 7, 2020)

Does that insert have any positive rake? What’s the nose radius?


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## Aukai (May 7, 2020)

The video sounds great, but no visual for the tool....


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## NortonDommi (May 7, 2020)

A guide for speed.  https://littlemachineshop.com/Reference/CuttingSpeeds.php


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