# severe chatter issues



## jason30809 (Feb 18, 2017)

Im new to posting but have been lurking about and reading for about a year but I have finally expended every avenue of problem solving I can possibly think of so I bring this question to you guys to see if anyone can help. Thanks in advance for your time and help. I have an atlas 10f lathe with an aloris style QCTP and a 6.5 in 4 jaw chuck and use mostly HSS but have had this problem with both HSS and carbide tooling. Over the past 8 months or so i have been fighting severe chatter while attempting to parts of just about all materials and diameters at just about all feeds and speeds. I have tightened all gibs, disassembled the head stock to check bearings and the spindle and both appear just fine. I have also tightened the pre load on the bearings to the point where run out is minimal while pushing on the chuck but eventually tightened to a point where the motor was working pretty hard to turn the spindle and the belt was wanting to slip so Backed off to as little run out as possible while still allowing the spindle to turn freely. All bolts that mount the feet of the bed have been properly tightened and shimmed 16 gauge sheet metal. This is a problem I didn't have with this lathe the entire time I have owned it but literally one day it was parting smoothly and the next the chatter was so bad it felt like major damage would be done if i continued the cut. The only piece of info they may be helpful to those with alot of experience with these lathes is that when cutting soft stuff like 6061 with say 1.75 in OD, the chatter disappears once i get down to about the last 1 inch of diameter of the parting operation. Guys i appreciate any help anyone can give. Im so frustrated and fed up with this problem that I have thought many times about just getting rid of the machine because if I cant part off then the lathe is pretty much useless for my needs. Its never been crashed while in my possession and no catastrophic event has taken place. I just dont get it and cant figure it out. I have looked for anyone in my area that is proficient with these machines but have come up dry. If a video is necessary i would be more that happy to provide that. Again thanks for your time folks. I forgot to add that the chatter starts only when the tool actually begins to grab the part and really start cutting. You know, the point where there is enough pressure to go from the tool rubbing and making powder chips, to the point where the blade engages the material and begins to produce properly formed chips. when those chips should start, instead the chatter begins forcing me to slow my feed and never be able to actually cut the material or feed the tool properly.


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## mikey (Feb 19, 2017)

Not sure what is going on but let's start the discussion and the other guys can jump in. 

So, if I understand correctly, you are experiencing severe chatter when parting off. The lathe parted well until one day when it didn't. You've adjusted and checked to make sure the machine is tight but it still chatters. The only positive is that when you reach the last inch of material, the chatter disappears. The chatter occurs at all speeds and feeds, which I take to mean you've tried different speeds and are power feeding with the cross slide to part off. Given that the lathe didn't chatter in the past, I assume you know that the tip of the cutter must be on center and that the blade must be perpendicular to the work; you are not a newbie at this parting stuff. 

Is that about right?

I'm going to assume that your blade is sharpened correctly, you know to use lubricant and you know how to part on your lathe - sounds like you do. 

It seems to me that something is moving. It may be the cross slide, compound, tool post or tool holder but something is moving. 

I'm wondering if the gibs in the compound or cross slide are okay. Because they're tight doesn't mean the gibs are adjusted evenly along their lengths so maybe check them? 

Is the tool post solidly mounted to the compound? With wear and tear the surface the post rests on may no longer be flat and that can lead to movement.
How well does the tool holder lock into the QCTP? How vertical is the blade in the holder? If it is the type of holder that cants the blade at an angle, the block that locks the blade can tilt the blade so you have to be careful to align the blade vertically.
If all this stuff checks out then I'm not sure what is going on. The fact that chatter resolves might suggest your parting speed is too high. As you get to the inner part of the cut, surface speed slows down and that suggests your speed at the start of the cut may be too high. You can try slowing down and see what happens. You can also try feeding manually to see if that helps; parting should be a smooth operation with a slight resistance to feed. Some guys feel that you should feed with a lot of positive pressure but I've never found that to be necessary when the set up is correct.

One more thing to check is the tool height. It works best when the tool is dead on center. If the tip is too high then you're rubbing; if its too low then you'll dig in. Many guys line up the tip with a tailstock center but that is not accurate enough. Either use a tool height gauge or machinist rule (trap it between the tool and the work and adjust height until the rule is vertical) but the tip needs to be on center. 

Okay, maybe some feed back from you and we can narrow it down further.


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## Round in circles (Feb 19, 2017)

I could have started a couple of radio stations with all the chatter I was getting  off my lathe .

 Here are a few of my suggestions before we get going off at a tangent & missing simple connected things ..

 Think & check every thing through logically in a set order

Make sure your tool is sharp & correctly ground . Cut the eye off a big sharp pointed darning needle . Set it in the chuck . point out to the tail stock , run the lather check it is running true . 
Now check the cutting edge of the tool against the point of the needle .. is it accurately set in line ?

It's best to slide the tailstock out the way to the right , remove any tools in it and eyeball it from the tail stock  along the center line axis .  Not having your eye lined up can give you a lot of error  ...I tend to put the cross slide to just past the needle tip looking from above the bed ...head over the axis .  Almost make the needle point  touch the cutting edge of the tool using the compound or saddle . Then wind the cross slide back till I can see it is aligned from above and along the horizontal axis from the tailstock view turn the chuck by hand 360 & recheck things  .   It took me a while to realise that I could be a few thou out if I only did it from one axis or was not dead in line with the  axis  .
 I have also checked ( & had to reset ) that the tailstock is dead on the chuck centre by putting a needle in the chuck & the tailstock chuck ... I found it easier than trying to use a steel ruler / scale  as I have a busted left shoulder & back problems .

  Have you also used engineers blue & the base of the tool post to check that the flat surface it sits on is perfectly flat  .....in all directions including caddy corners ( the diagonals ) ?

My new to me lathe had several thou of hump where someone had pulled a hardened bolt up the mounting / Tee slot to secure the old lamp post tool post . When I tried to part or do an internal bore the pressure of the cut was enough to ever so slightly cause the tool post to rotate a few thou or more as well as busting a few parting blade it chattered a lot . 
It took a while to find out why it chattered so much , but after I discovered I'd cut cone shaped holes & cured it  as above things got better ...much better .

Do you also have enough thread on the anchor bolt to ensure things are fully home when you have tightened the tool post .  ie  Is the bolt shank is stopping the nut going fully home ?

 Tool grabbing into the metal .

 My little experience tells me , it is often is the result of cross shaft free play being suddenly taken up usually by the cross gibs not being tight enough & or the saddle gibs being slack .

 ... Have you checked the ways of the lathe with a decent steel ruler / scale to see if they are badly worn ?

 When parting do you lock the saddle to the bed ( you should  ) as well as ensuing that the gibs are not slack / too easy to slide ?

 When you start the parting  always wind the wheel out so the tool cutting edge is a 1/4 " or more away from the work piece then gently start to advance it to the work piece & into it at an even speed , so it takes a thin curl un blued by heat off the piece rather than chipping it off . Use both hands to try & keep the tool moving at an even speed once you get taking material off .


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## jason30809 (Feb 20, 2017)

Awsome questions guys, i think i can narrow down a few things that might help yall figure this out. The tool post seems to lock just fine and always has but i have not check with layout fluid i have tightened gibs from the saddle to the compound from being nearly unable to move the saddle cross feed and compound to being easy to turn. I always hand feed in the tool and always lock the carriage im sure if i used powerfeed the tool would definitly catch and either break off or cause the part to ride up on it and stall the machine. I probably shouldnt use the word "chatter" to describe whats happining because that suggest an annoying noise and bad finish. What im dealing with is a horrible vibration that makes you think "something major is about to break". its to the point where yesterday the nut holding the compound handle on vibrated off the machine and onto the floor. I litterarly cannot part anything at all with this thing. Its to the point of feeling dangerous. Something is seriously wrong here and I just dont understand it. Another thing that may help out is when im feeding the tool in, right as it gets to the point were the tool would bite into the material and start producing nicely curled chips, the feeling i have in my hand coming from the cross slide handle, is like the cross slide is kind of floating toward the material. Almost like reverse backlash if that makes sense. At least it seems like im getting that feeling from it but i could be wrong because the vibration is so intense. Like i said earlier, i dont know if its possible to upload videos on here but if that would help i can try to record this massive vibration. Thanks again guys


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## wa5cab (Feb 20, 2017)

Put your left hand on the front of the compound slide and pull firmly toward you as you advance the cross slide with your right hand.  If that changes things, the parting tool is dragging the cross slide forward and itself into the work.  There is always some backlash between the cross feed screw and nut.  Possible causes are parting tool not on center coupled with gibbs too loose.  Parting tool not ground right.


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## jason30809 (Feb 20, 2017)

as far as parting tool positioning i have tried dead center and a little below and as far as the grind goes i get the same result with standard parting blade ground to about 5 degrees front rake and stoned smooth, an 1/8in ground tool and indexable carbide blade. Something is physically wrong with some part of this machine i.e. something worn, broke or loose or something like that. I know the basics always have to be asked but trust me over the last few months i have tried every form of tool and geometry that has ever been written in just about every book and if the gibs get any tighter i wont be able to turn the knob. something else is going on. Its hard to describe how violent and severe the vibration is. this is really really bad


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## jason30809 (Feb 20, 2017)

just tried pulling back on the cross slide and no dice. still major vibration.


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## wa5cab (Feb 20, 2017)

OK, you have to pull back pretty hard for it to make an audible difference.  It isn't a practical solution, but when you described the "floating feeling", I realized that I had had a similar problem while trying to use a full 90 degree form tool to put a large radius end on some 1" diameter copper electrical connectors that I was trying to make.  The cross feed crank felt just like it does if you have a fair amount of backlash in the cross feed, put the crank into the middle of it, and then rock the crank back and forth.  Takes virtually no force.  I think that something is different about either your parting tool or how it is being held.  But I don't know what.


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## jason30809 (Feb 21, 2017)

just to see what happens I locked down all gibs pretty much as tight as i could get them including the cross slide and went for a cut in 1.75 in aluminum. This appeared to have made a difference. the vibration was still present about 1/5 of the way into the cut but it was far less severe than it was. The problem is that where i had the gibs tightened to was more of an experimental setting than a functional setting because i really had to tighten then down tight......real tight. I think this takes my worrys out of the head stock and and into the carriage/cross slide/ compound/ QCTP.


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## brino (Feb 21, 2017)

That sounds like some progress. Hopefully now you can try one, or two at a time and figure out the source of the movement.

One other piece that I have NOT seen mentioned is the spindle speed. There is a HUGE difference between the surface feet per minute at a diameter of 1/8 inch and a diameter of 2".  SFPM = dia.[in] /4 *RPM

See my comments here: http://www.hobby-machinist.com/threads/soft-jaws.55689/#post-460870

Please let us know how it goes.

-brino


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## stupoty (Feb 21, 2017)

Might be worth looking for small fractures that might have opened up or a rogue piece of swarf trapped in the ways or gibs.  Pull the compound and cross slide off and clean and oil and reassemble whilst having a look.

Always annoying when something that used to work stops working 

Stuart


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## Round in circles (Feb 21, 2017)

Hmmmm,  one thing we haven't suggested  but should have looked at first before we progresed to the cutting parts 7 other things mounted on the saddle etc .

Bearing & gears check ?
My new top meSphere cum Atlas lathe had so much crud in the head stock bearings on both sides it 's a wonder it could rotate .
( My head stock bearings are 3 inch taper roller bearings lubricated by grease by the way )

( If there are any meshed gears on the gear box end leave them in place undisturbed at present  )  Get a  2 foot long 2x2 thick baton of wood  stick  & block of wood  , so you will be able sit the block on the ways under the chuck to lever off the block , to press the stick on a smooth area of the chuck .........   before you start secure the tail stock to the right hand end & move the saddle to the right  end & use a pair of decent protective gloves to help prevent splinters in your hands  .

 Start the lathe fairly fast , lever on the block with the stick somewhere near the rear of the chuck .. does it make any noise or cause undue vibrations
 If none put a  4 inch long thick round bar in the chuck so it protrudes 2 .5 inches , tighten it up  & repeat..... this time pressing the lever up on to the bar top ... any difference in noise ?


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## jason30809 (Feb 21, 2017)

i will have a go at this and let you know how it goes. Just to be clear am i putting my lever block on a smooth part of the chuck to push on it while the chuck is moving?


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## woodchucker (Feb 21, 2017)

So I had an issue where my parting tool was chattering. I tried re-grinding no improvement.  Finally I bought a new piece of tooling. Problem solved. I think there is a microscopic crack in my bad parting tool.


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## Round in circles (Feb 23, 2017)

jason30809 said:


> i will have a go at this and let you know how it goes. Just to be clear am i putting my lever block on a smooth part of the chuck to push on it while the chuck is moving?



Yes,  to see if it induces chatter ,when it's close to the back of the chuck ,    doing it on the end of the bar puts a bit more pressure on the bearing  again to show up chatter .


 Reading the above post do you get still chatter when winding in a different cutting tool to your parting off one ?


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## T Bredehoft (Feb 23, 2017)

Probably not  your solution, but I  eliminated a bunch of chatter by slacking off the tension in my drive belt. It was transmitting hum from the motor to the spindle of the lathe.


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## pdentrem (Feb 23, 2017)

I found the top slide on mine was worn at both ends. Once I ground/lap it flat a lot of the chatter I was getting was reduced. Later I made a new top slide that was longer and dead flat, what a difference!
Pierre


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## Round in circles (Feb 24, 2017)

As I stood by my lathe turning up a cup / holder that will fit in the drill, press or a tailstock chuck to hold a button type threading die I though more about chatter & could I find an easy way to locate it  . . 

 Turning the internal part of the cup to take the die I found several ways of getting chatter .
 One was cutting tool flex as it was sticking out the QCTP by a good 70 mm . Others were  incorrect tool tip height , wrong cutting & clearance angle & wrong cutting speeds either too fast or too slow  .  Having the drive belts a bit too tight also gave a bit of chatter type  noise .


  I decided to try something to see where else unwanted movement was on my lathe .


 I stopped the lathe , brushed off all the noticeable crud  .  sprayed it with WD40 , cleaned it off with a soft lint free miracle fibre cloth  , then sprayed it but very lightly , again with WD 40 on the ways & also at every point of contact where the saddle , cross slide & compound slide touch each pother . I also included the QCTP & tool holders in the light spraying .

I then ran the saddle & slides back & forth to flush out any hidden stuff . Set the lathe running & started to take heavy cuts off a slug of round steel . With all the man cupboard lights on it &  using a magnifying glass ....it was easy to see  tiny microscopic movements in the meniscus  of the WD 40  at the join lines of the ways slides & QCTP . 
 I  then cleaned the tailstock runway , set up the tail stock , centre bored the slug & put the tailstock live centre on the bar , again did the light spraying & whilst doing a heavy to the chuck cut  observed the meniscus under the magnifying glass .

 The QCTP  is best set mid way of the compound slide travel & nigh on locked with the compounds gibs for if it is fully to the chuck  you have lengthened the lever by a couple of inches & this does tend to give a fine cockle shell looking finish & light screeching  chattering  noise .  If you want to use the compound it's a matter of a minute to slacken it off enough for the job . & a minute again set it tightish at the half way point  when you've  finished.

 Pleased to say nothing was dramatically out of order,  but I've proved that you can see places that may be the cause of chatter .


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## brino (Feb 24, 2017)

Round in circles said:


> ...it was easy to see tiny microscopic movements in the meniscus of the WD 40 at the join lines of the ways slides & QCTP .



Good eye David, I have noticed that too on the big dovetails of my mill with a heavier oil, the "juice line" seems to wiggle with any movement in the joint.
-brino


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## markba633csi (Feb 24, 2017)

I hate parting off. I avoid it like the plague LOL
MS


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## fitterman1 (Feb 25, 2017)

Hi everyone, reading through this post and noticed that tool heights mentioned here were set at center. I was taught to set it at 2-4 thou above to counteract spring in the blade and therefore it will sit at center under load. If at center or below, when under load it will definitely chatter as it cuts and springs back up into position. Or starts to rub rather than cut if sufficiently low. Also there is a change in top rake of a few degrees which may have minimal impact depending on the material. 

Jason says "when cutting soft stuff like 6061 with say 1.75 in OD, the chatter disappears once i get down to about the last 1 inch of diameter of the parting operation."
My reply to Jason is - this  is the window where you have your speed and feed correct.
If you watch a cnc lathe parting off, it speeds up the closer it gets to center. Realistically we cant do this with our machines, we set speed to cover the entire operation and adjust feed to suit.

"when those chips should start, instead the chatter begins forcing me to slow my feed and never be able to actually cut the material or feed the tool properly"
This is another issue I have had with apprentices mainly but also tradesmen, they back off their feed when the chattering starts. They should be increasing their feed at this point until they see their little clocksprings coiling up and jumping out.
At the end of the day machinetool rigidity and correct setting of tooling in conjunction with optimum speeds and feeds gets the job done quickly and the nerves are not so shattered.


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## bfd (Mar 2, 2017)

most of the chatter I find is from too much speed. my story is on a 12x36 frejoth lathe. turned my front disc rotors on my lathe and could not stop the chatter at the slowest speed. got it as   smooth as possible with emery cloth and thought it would work. so reassembled my brakes and tested them. well they worked too well, almost went through the windshield the first tap.took them back off and re pulleyed my lathe to 30 rpm ( from 60 rpm) and recut them much better, but first I tried all the tricks like wrapping a bicycle inner tube  around the part this helped some but not enough. moral to the story doun use disc braked if the surface looks like a fine file bill


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## jason30809 (Nov 6, 2020)

guys im back. I was never able to find the problem and  finally gave up on it. After 5 years of it sitting idle and the work I need to use it for piling up, I decided to do some searching and see if i could find an answer and came across this thread. Does anyone on here live around Augusta ga? I have come to the realization that I need to somebody to see this with their own eyes and you would be surprised at how hard it is to find old school machinist that know these old machines like the back of their hands. If anyone lives around here it would be great if you could take a look. I feel like something is cracked or broken or worn. I really think one of yall would find the problem within minutes. All i know is whats not causing the problem .... its not tool height or feeds or speeds because i have literally tried them all. Geometry of parting tool doesn't matter either because i have tried them all. I have double and triple checked the easy stuff like that. now im convinced something is broke i just can figure out what. Someone mentioned the chatter decreasing as i got closer to the center of the parting operation so they think it could be a feed speed thing... I have tried just about every combo of feed and speed i can think of but something else that happens towards the center of the part being cut off is the force pushing down on the tool also decreases and i think that might have some relationship with why the chatter decreases toward the center of the cut. Anybody that can help would be so greatly appreciated. thanks


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## brino (Nov 6, 2020)

Hi Jason,

If you cannot find a local, knowledgeable volunteer, perhaps you can take video with your phone and post it here.
I have successfully posted *.mp3 videos to this forum.

Two other things:
1) On my 9" Southbend I initially tried parting with a thin blade(1/16") thinking that the cutting forces would be reduced and it would lessen chatter.
That did NOT work!
I have to use a thicker parting blade(3/32"), and I believe it has to do with the stiffness of the tool.
I was surprised the difference that small looking change made.

2) I have seen once where the t-nut that holds the tool post to the top slide was too thick. It caused the tool post to be able to rock on that small mating surface. Once the t-nut was cut down the problems went away.

-brino

edited to fix widths.


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## Grinderman (Nov 6, 2020)

Check your upper compound slide where the tool post mounts. I've seen a couple of these that were cracked in the T-slot area. I finally went to a steel version.


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## fitterman1 (Nov 12, 2020)

Hey brino, 1/16th is smaller than 3/32nd in my book.
Swap your numbers around to prevent confusion mate.


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