G4003G Lathe Help needed

I

IanRobertson

New member
I have been having problems with the quality of cut. I decided to change the bearings after I had a pattern and could not get rid of it by tightening the preload and still had measurable movement when I pushed sideways on the chuck with one finger. After the new bearings were in I adjusted preload until there was no movement either way and it seemed to run fine with no heat up. The picture tells the tale. The ridges can be felt and are very pronounced. This was cut using the threading feed at 112/inch but it is the same using the power feed as well. Can't find anything else wrong, are the new bearings too loose? Thanks for the help.
ripple effect 4003.jpg
I learned a lot about bearing. I contacted both Timken and NSK and I was told the same by both companies. The only bearings that are available under the part numbers are a standard ISO size bearing of standard quality. Both companies said it would not matter whose bearings I used, both are the same quality. They both said that these bearings were not really of the quality or type to be used in a lathe due to the subjectiveness of applying pre-load saying there were better alternatives but not a direct replacement. NSK offered to have a rep come by and see what he could prescribe. The original bearings, which died under 100 hours were XYS brand, China. Grizzly was of little help diagnosing the problem and when I suggested perhaps an extended warranty due to the short life, no. I ended up buying Timken which I found locally for much less that Grizzly prices, NSK was also available for about the same price. NSK appears to be what Grizzly now sells. The Timken bearings were made in Italy and Poland, there are two different main bearings. Now to get a decent cut!
 
Last edited:
I get this kind of cut sometimes turning between centers at the tail stock end or towards the middle. In my case it seems to be flex in the barrel and I can cure it by slowing the rpm. I think a vibration caused by the lathe dog is the issue with my lathe.
 
Last edited:
Ian,

I experienced something similar with my old lathe, a Cut King 16X40 (Taiwanese). I fought, cussed, and carried on, trying to rectify the bad finish. Speeds, feeds, re-leveling, different chucks...you name it. I even took the headstock OFF and cleaned the bearing surfaces between it and the bed. Eventually, I tore everything apart and replaced the bearings with some primo types. Started taking test cuts...same bleeping thing. A for crap finish.

Then one day, for reasons un-remembered, I was putzing about with the motor, loosening and re-tightening the motor mount/belt tension. Shortly thereafter, I took a cut and wala...a nice finish. I ran different speeds, different feeds, and different materials. The finish was nice in each case. Never had a problem with it again. That particular lathe now lives in a friends machine shop where he and his help are completely happy with it.

I figgered something got a bit off or out of balance with the motor pulley assembly and was causing a vibration, which resulted in the bad finish. Might wanna give that a whirl...

Hope it helps,
Justin
 
There was a guy on this site last year that was having a very similar problem, and he fought with Grizzly and finally found a fix and posted it on this site. I was just searching for it but can not find it, but as zebra13 said this guy found it to be motor vibration and posted the fix which involved taking the motor mount apart and inserting a piece of hard rubber in between the mount and where it hooked up to the lathe. there was also a second part to the fix but I can't remember what he did. He also said he got the piece of hard rubber off of ebay. Maybe someone out there remmbers this or can assist with info from the original poster!
 
IanRobertson said:
I have been having problems with the quality of cut. I decided to change the bearings after I had a pattern and could not get rid of it by tightening the preload and still had measurable movement when I pushed sideways on the chuck with one finger. After the new bearings were in I adjusted preload until there was no movement either way and it seemed to run fine with no heat up. The picture tells the tale. The ridges can be felt and are very pronounced. This was cut using the threading feed at 114/inch but it is the same using the power feed as well. Can't find anything else wrong, are the new bearings too loose? Thanks for the help.
View attachment 12295
I learned a lot about bearing. I contacted both Timken and NSK and I was told the same by both companies. The only bearings that are available under the part numbers are a standard ISO size bearing of standard quality. Both companies said it would not matter whose bearings I used, both are the same quality. They both said that these bearings were not really of the quality or type to be used in a lathe due to the subjectiveness of applying pre-load saying there were better alternatives but not a direct replacement. NSK offered to have a rep come by and see what he could prescribe. The original bearings, which died under 100 hours were XKS brand, China. Grizzly was of little help diagnosing the problem and when I suggested perhaps an extended warranty due to the short life, no. I ended up buying Timken which I found locally for much less that Grizzly prices, NSK was also available for about the same price. NSK appears to be what Grizzly now sells. The Timken bearings were made in Italy and Poland, there are two different main bearings. Now to get a decent cut!
Click to expand...

Something is loose and/or out of balance................show us several photo's of your entire lathe and setup for more specific ideas............Don
 
If i am not mistaking the post was made by Jay Cutright. Jay is a friend of mine and yes he used some rubber to help absorb the vibration. I also think he went with a 3 phase motor. I think!! I will see jay here in about 2hr. I will ask him and have him post when he gets a chance. Search Jay cutright user name and see if you cant come up with something. Lee
 
I just found it and its by eww1350, not sure who he is but he difinately had or has the solution most of the photos on page 1 have been removed but there are pictures on page 2! It was also a Grizzly 4003G. the thread was titled "Thread Chatter on 4003G finally resolved"
 
Last edited:
What type of material are you cutting?
How much material is sticking out from the jaws?
Are the jaws clamping on a straight or taper section of the material?
What type of tooling are you using, carbide or HSS?
Have you set the tool at or just below center of the work peice?

Try an rpm of 800 with a feed rate of .004" - .006" per rev.

I'm with Don, something looks loose like the work peice is moving.
 
Don....I had some chatter issues when threading with my 4003G lathe...but the looks of your work piece makes me think something is loose in your setup...I do not know how much lathe experience you have...so if you know how to set up a work piece and tool properly...then it could well be you need to check you drive motor pulley and the the small driven pulley that your two belts are running on...I found on my lathe and another...that the set screw was loose as it came from the factory...check those pulley set screws..!!!....most of the chatter problem originates at the motor...check it carefully...I also took one of my belts off and run a loose belt NOT tight...


Good Luck...
Eddie in Texas
 
Last edited by a moderator:
Thanks for all the replies.

I did review the old posts prior to changing the bearings to learn as much as I could.

It is a used ss barrel, not tapered, held solid in a Bison 8" set true chuck, about 3" out, gibs have been adjusted on both, motor is on rubber and belts replaced with a single link belt, motor turns nicely, pulleys tight. Same effect with HSS or carbide (picture is HSS), much the same with different feed rates and rpm's, all light cuts. It didn't do this when new.

All I can think is the new bearings don't have enough pre-load, I will check run out again now that I have run it a bit and also check pre-load. After a 20 minute run there is no warmth from the bearings and perhaps there should be??
 
IanRobertson said:
All I can think is the new bearings don't have enough pre-load, I will check run out again now that I have run it a bit and also check pre-load. After a 20 minute run there is no warmth from the bearings and perhaps there should be??
Click to expand...
There should be a slight temperature rise, medium warm but not hot if that makes sense (120F or so).

On an end-play test with a 0.0001" dial indicator you should tighten to where no measurable end-play can be seen, then go a slight bit more. If you have a lead hammer or a billet of lead (like a bullet pouring ingot), peck the ends of the spindle being careful to not jar the dial indicator.

Then take a cut with a HSS, lipped, tool of about 0.025-0.050"/side and about 0.002" IPR feedrate. Then post a picture of the results.
 
Been at it all day. I tightened the bearings, runs just warm after 20 minutes at 1000 rpm. Certainly improved with the bearings tighter, last thing I did was to loosen off the drive belt more and I think it's there now. The cut was done with the same tool, .002 feed, .025 off etc. to compare. You can see a very slight pattern now but you can't feel it. I also used a cut off tool to cut off a stub and I had no chatter. Does this look okay?? Is there any pattern like this on the old standard makes of lathe? Perhaps I need to be looking for some old iron! The part in the picture is half new cut and half the old as per the old picture.
View attachment 12301
 
IanRobertson said:
Is there any pattern like this on the old standard makes of lathe? Perhaps I need to be looking for some old iron! The part in the picture is half new cut and half the old as per the old picture.
View attachment 12301
Click to expand...

I can't display your attachment. The site www.postimage.org works pretty well. After uploading, pick the first selection of the third group.



(This is my new 2012 600 yard gun)

As to looking for some old American iron, I'll vote for that.
 
One reason for that strange finish is the overly large tool nose radius. This spreads the cutting force over an excessively large area.
For an application like this 0.005" or so nose radius is sufficient.

Some nose radius is necessary to spread out tool wear but what you have gives the effect of a large forming tool.

Also, looking at the "tearing"in the 10-11 o'clock position looks like you either don't have enough bottom clearance, the tool is getting dull, or, the tool is above center.

We're still trying to make a silk purse out of a poor quality machine.
 
I believe the issue is the single-phase motor.

I had a motor on a Baldor (!) 8" grinder, which I eventually gave away, which growled horribly. I found it hard to believe that the vibration was normal. Took it to a local motor shop where they balanced the arbor, put in new bearing... the works. Zero improvement.

So, I started researching the motor. It was a 3650 RPM motor. I noticed in the MSC catalog that motors of this RPM were considerably cheaper than 1800 RPM motors. The reason: half the copper. Then I noted the weight of the 3650 RPM motors offered, particularly the high quality ones. The weight of my offending motor (of similar HP, of course) was much lower.

Apparently, in motor design there is a trade off between how much copper ($$$) you put in your motor and the smoothness of the rotation. This has primarily to do with the number of poles in the motor design.

I had a JET 1340 which produced similar patterns. I started formulating a plan to solve the problem, when fate intervened and I replaced it with a Haas TL-1. Therefore, I don't have much gas behind my recommendation, although others have concluded same, and have implemented it. And it is this: covert to a three-phase motor of decent quality and a VFD.
 
One comment I would make is the eveness of the chatter/pattern. This would lead me to think the problem is coming form an out of balance drive system. The pulleys on some of those "cheaper" machines don't run very well. I would also have to agree with what Jerry said about tool geometry.
 
I did notice that the pulley only has the paint worn off in one spot so it must be waving back and forth. I will tune that up as well. Working much better now for what it is. Thanks for all the ideas and PM's.
 
There is certain cheap structural steels that will do this no matter what . They vibrate and can ring like a bell.
Replace the steel you are using with a harder steell ilke D2 and see if that helps.
Make sure the job is supported properly and if between centers the tailstock center is tight enough to resist sloping about and lubricated .
Makes sure the spindle speed is fast enough for the cut .
Start with indexabel inserts to learn turning and later grind your own tools . Choose an insert with a fine point radius for finishing cuts and a larger radius for roughing cuts . Finish at a higher spindle speed and lighter cut than roughing.
Make sure the compound is tight on it's dovetail and that you don't have it over extended. Make sure the lathe is level and all feet are on the floor solid.
 
You must log in or register to reply here.
Back
Top