Grizzly 4003G Lathe Chatter Problem

[dave2176]

The bearings that came out of it were clearly marked as NSK P5 grade bearings. The bearings that replaced them are ISOClass Timken bearings. That only means they follow that specification of measurements. While Timken leads the charge on quality, those bearings are not identified within the Timken high precision catalog. Rather they are in the standard bearing catalog and while I haven't finished reading the 800+ page catalog looking for clues about their ratings, it appears they do not carry an ABEC or ISO P rating of any kind. I would suggest replacing them with at least ABEC 5 or P5 bearings. Timken has this to say about downgrading bearings:

"it is not recommended to fit standard class bearings in place of the original precision ones. This practice would most likely result in uncontrolled movements of the spindle due to the higher runout of standard bearings. This can lead to poor accuracy of machined pieces and premature tool wear."

Best of luck,
Dave

 

[Jamespvill]

Do you have any viberation in the lathe? Have you moved the lathe location or added enything. Any new equipment with large power transfomer running. If nothing has changed use the live center cranked pritty tight. If you still have chatter then it is in the too down squealing is usley tool set above center or dull. aAlso try 200 to 300 rpm 600 might be to fast for 316.

I had very little vibration prior to the machine having this issue. Since it started, it's now on rubber feet and I have even less vibration. I have turned a piece with my live center much tighter than I prefer and the problem still remains. Ive also checked and rechecked for tool height, its right on center, and Ive tried below and above center, no difference. I have also used a new side of a indexable carbide insert with each subsequent test (I'm almost out of unused bits by now!) Different speeds and feeds also result in the same poor finish. Oddly enough, when I turn 1018, I don't get much squeal but the finish is so rough that I could use the piece as a fine rasp for wood.

While I am by no means a seasoned professional in the shop I used to manage fantastic finishes with all of these feeds and speed. Heck, I had to try hard to even get a bad finish on most materials. Thats what concerns me the most...

 

[coolidge]

James I'll ask again, does it chatter taking a face cut?

 

[Jamespvill]

The bearings that came out of it were clearly marked as NSK P5 grade bearings. The bearings that replaced them are ISOClass Timken bearings. That only means they follow that specification of measurements. While Timken leads the charge on quality, those bearings are not identified within the Timken high precision catalog. Rather they are in the standard bearing catalog and while I haven't finished reading the 800+ page catalog looking for clues about their ratings, it appears they do not carry an ABEC or ISO P rating of any kind. I would suggest replacing them with at least ABEC 5 or P5 bearings. Timken has this to say about downgrading bearings:

"it is not recommended to fit standard class bearings in place of the original precision ones. This practice would most likely result in uncontrolled movements of the spindle due to the higher runout of standard bearings. This can lead to poor accuracy of machined pieces and premature tool wear."

Best of luck,
Dave

Keep in mind I have just about 0 knowledge of bearings past that of what they are intended to do. I called up my "local" (1.5 hour round trip) bearing supply store and talked to a gentlemen who guaranteed me that not only were Timken's the best in the world, but also that they were the best bearing to be putting in my lathe.

Now with this nugget of knowledge, I don't think I approve of that mans business practice...I highly doubt that they take back used bearings either! I also brought my other bearings in and he guaranteed me that those bearings were no good anymore. I have a few colorful words that I would like to share with him now that I think of it.

So now I'm curious about bearings... What is the general opinion of Japanese-made NSK bearings? Im assuming the class is the quality, but what is ISOclass then? Is there a generally agreed-upon order of what bearings are the best for lathes and precision equipment?

Thanks for the information, Although it does make me a little more frustrated, new information always falls on welcoming ears for me.


On a side note; Although these bearings aren't the appropriate ones for my machine, it didn't change the performance of it in either a negative or positive way, so Im hoping that the bearings weren't the problem to start with.

Also, should I put my old ones back in then?

- - - Updated - - -

James I'll ask again, does it chatter taking a face cut?

Oops, I may have neglected that one! But yes it does. It chatters on a face cut going in or coming out. It also chatters when going left or right when doing OD turning. I've completely locked my cross feed and compound for cuts and that makes no difference. I've also applied quite a bit of pressure to the carriage lock for cuts, once again, no difference.

Sorry I missed that one!

 

[Jamespvill]

I receive a PM from another user saying that he had the same problem and it ended up being a crack in the crossslides casting...Gonna have to double check that I don't have any cracks in my machine.

 

[coolidge]

Look inside both lathe stand cabinets, if there is a weird looking creature living in there I think you found the problem...Gremlin. lol I don't know man I'm baffled. This is about the time I would get major PO'd, start cussing and rip everything apart to inspect and clean.

 

[Ray C]

The bearings you pulled out were worn/damaged. Even after long years of service, the races should be polished looking like chrome. Your old ones were scuffed-up. All that glitter in your oil that you reported was probably ground-up bearing material. -Either that or a bad gear. After my 1st oil change, there was nothing in the way of glitter in the oil.

I don't know how it would happen but, I almost think your spindle is bent. Maybe it was born that way and first now wore-out the bearings enough to show symptoms. A bent shaft causes all kinds of hell on taper bearings. Another possibility is that the casting holes are not even and the shaft is spinning at an overall angle. This too will damage taper bearings because they cannot tolerate anything but perfectly aligned axial or radial forces. Angular force is a no-no for taper bearings and that's why they make angular force bearings that can tolerate up to 10 degrees of motion.

High precision bearings are a different breed of animal. Here's a good link that gives some insight: http://www.skf.com/group/products/b...es/bearing-data-general/tolerances/index.html Most of the bearings I'm familiar with for lathes that size cost well over $200 each (closer to $300) and I was very surprised about the price you got them for.

How old or how many hours of use are on the machine? And just for the sake of completeness, do all the leadscrews and feed rods spin OK by hand? -Really more a question out of curiosity but at this stage of the game, we can't rule-out anything.


... Checking the machine for cracks was a good suggestion. Also, have you checked the hold-down tabs underneath the carriage? There are tabs that keep it from coming up. There should only be about 1-2 thou clearance and they are shimmed at the factory. -Just check e'm to be sure.


Ray

 

[Jamespvill]

Well it's good to know that my previous bearings were actually damaged to the point of needing repair.

I had assumed that the glitter party at the bottom of my gearbox was just residual machining material that never found it's way out after the first few flushes...I have changed my oil 6 times up to this point I do believe.

I originally called Grizzly see what the cost of replacement bearings would be, I was told around $40 for the small and $80 for the larger. So I wasn't at all concerned when the Timkens were just a few dollars more expensive. I assumed that Grizzly was actually over-charging for their bearings, as they do with a lot of their accessories. Now that I know the price should have exceeded $400 for the pair, I'm...in a word; confused.

When not engaged both the feed rod and the lead screw spin very freely. I cant find any hold-down tabs that you mentioned. The manual refers to this guy as the carriage gib though. Thats been tightened very tight and no difference.



Oh...It's upside down...thats nice. Anywho...Imagine thats the back of the carriage, and also imagine that It's also a lot less upside down. Also, While your at it, Imagine the machine that is attached to is providing its owner with nice finishes on its work.

I've had the lathe since August of 2012, brand new and a painful experience from my pocket at the time. On a active month it gets 40-70 hours on it, on a slow month it gets less than 30 usually. All machining is done by me, no one else touches my machine! I think the rest of my family is too scared after I almost lopped off two of my fingers with it.


Haha! Just found this; My Lathe ----> :*****slap2: <---- Me

 

[Ray C]

Well it's good to know that my previous bearings were actually damaged to the point of needing repair.

I had assumed that the glitter party at the bottom of my gearbox was just residual machining material that never found it's way out after the first few flushes...I have changed my oil 6 times up to this point I do believe.

I originally called Grizzly see what the cost of replacement bearings would be, I was told around $40 for the small and $80 for the larger. So I wasn't at all concerned when the Timkens were just a few dollars more expensive. I assumed that Grizzly was actually over-charging for their bearings, as they do with a lot of their accessories. Now that I know the price should have exceeded $400 for the pair, I'm...in a word; confused.

When not engaged both the feed rod and the lead screw spin very freely. I cant find any hold-down tabs that you mentioned. The manual refers to this guy as the carriage gib though. Thats been tightened very tight and no difference.

View attachment 73881

Oh...It's upside down...thats nice. Anywho...Imagine thats the back of the carriage, and also imagine that It's also a lot less upside down. Also, While your at it, Imagine the machine that is attached to is providing its owner with nice finishes on its work.

I've had the lathe since August of 2012, brand new and a painful experience from my pocket at the time. On a active month it gets 40-70 hours on it, on a slow month it gets less than 30 usually. All machining is done by me, no one else touches my machine! I think the rest of my family is too scared after I almost lopped off two of my fingers with it.


Haha! Just found this; My Lathe ----> :*****slap2: <---- Me

Yes, that's the rear jib. Unless the design is different, there should be two smaller tabs in the front (one on left side, other on right side). Kinda hard to get them out but unless you take the carriage off, you won't need to. Lift up on the carriage. You shouldn't be able to lift it any appreciable amount. The tabs should roughly be a near zero-tolerance fit that still allows the carriage to traverse freely. Same for the rear one.

Do an experiment for me... lightly apply your carriage lock just enough so there's a little resistance but still lets the carriage move then, take a cut. Let me know if you still get the chatter.

What's the material you're cutting? type of cutter? Looks like carbide cut with a slight chip in the insert. Just entertain my questions if you don't mind. There's always a possibility we're chasing 2 (or more) problems and I'm ruling things out.


Ray

 

[Jamespvill]

Yes, that's the rear jib. Unless the design is different, there should be two smaller tabs in the front (one on left side, other on right side). Kinda hard to get them out but unless you take the carriage off, you won't need to. Lift up on the carriage. You shouldn't be able to lift it any appreciable amount. The tabs should roughly be a near zero-tolerance fit that still allows the carriage to traverse freely. Same for the rear one.

Do an experiment for me... lightly apply your carriage lock just enough so there's a little resistance but still lets the carriage move then, take a cut. Let me know if you still get the chatter.

What's the material you're cutting? type of cutter? Looks like carbide cut with a slight chip in the insert. Just entertain my questions if you don't mind. There's always a possibility we're chasing 2 (or more) problems and I'm ruling things out.


Ray

Okay, I must have missed the tabs then. Regardless, when the problem first started I lifted up on the carriage to see if it was loose at all, no movement that I can tell.

When checking all the gibs and locking the crossfeed and compund down I also tightened the cariage lock down too, then did some turning by and and auto feed. No noticeable difference.

My first thought was chipped carbide insert also, so I swapped it out. Every single test I am doing I am also swapping to a brand new edge, Im due to run out of new edges very soon.

Here are the photos that I sent off to Grizzly tech support of my finishes that I am getting on a variety of flavors. While it is by no means the worst finish in the world, it is nothing like it used to be and there are deep lines and chatter on the piece. Even on 12L14 and Aluminum where I used to get magnificent finishes...I now get rough and unacceptable finishes. I can't even fathom sending out a barrel with these finishes on them! Anywho, the pictures below show 316 SS, 6061 Alu, and 304 SS, respectively. Three cuts on each at 10, 20, and 30 thou depths. All at 600 RPMs (Not exactly the appropriate speeds, but It worked perfect before) and at .0044 inch/rev. The SS was cut with a SS specific insert and the Aluminum was cut with an aluminum specific insert.






(EDIT) Looking back at all of those cuts, I realize they all scream "Chipped Insert!" but I promise, that is not the case, Pinky promise! I feel like Ive eaten up a lot of everyones time for it to be something that simple, And I have been running my lathe almost daily for the last year and half, I would certainly hope something that simple wouldn't stump me that easily.