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  1. #1
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    Grizzly G4003G Lathe

    I have a Grizzly G4003G gunsmith lathe which I bought in 2010. It had a lot of great features and tooling for the price. I like it in every way except I have had one problem from the start. It leaves a "harmonic" pattern on any turned surface. It does not seem to be related to feed rate because it happens no matter what feed I choose and also when I hand feed. I have assumed it is in the headstock bearings. I have played with the pre-load on the bearings but this hasn't helped. It is a geared head and I wondered if this could play some role in the problem. Has anyone experienced this with other geared head Chinese lathes? If so, were you able to overcome the problem? I would appreciate any suggestions. Thanks, Kent.

  2. #2
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    Re: Grizzly G4003G Lathe

    I have the G0750G lathe which isn't too much different. It has better bearings and an enclosed gearbox, and yes, I get the same problem. I have tried various feeds and speeds, but I wonder if it is due to the machines vibrations? Until I put it on the concrete floor (from the wooden table its on) will I know. I just thought it was the crap-tastic shars carbide indexable bits I used. My old harbor friend mini 7x10 lathe left better finishes. But in any case here are some parts I just turned with it:



    The best thing I found so far, was to change the upper gear to a smaller gear other then the 60, which made the auto feeds much slower, and more tolerable finishes.

    You can sort of see the horrible finish on the top of this one:


    I do really think its the about of machine vibration. Are you using the cheap metal stand it came with?

  3. #3
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    Re: Grizzly G4003G Lathe

    Here is the table which it is bolted on:



  4. #4
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    Re: Grizzly G4003G Lathe

    The company I work for also using Grizzly G4003G , and have almost the same problem ..

  5. #5
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    Re: Grizzly G4003G Lathe

    It seems like it may be more than just an isolated case. I have been corresponding with a Grizzly Tech who said that I should try using rubber pads between the drive motor and the lathe. When I checked my lathe it has rubber pads from the factory. His next suggestion was to replace the headstock bearings. I have them ordered but I am not very hopeful that this will solve the problem. I am inclined to believe that it may be a combination of things. First, the headstock casting is very thin. There is not much metal around where the bearings are mounted. This could be part of the problem. Second, these bearings may not be designed for the type of loads that lathes are required to take. Third, the gears in the headstock may just impart some vibrations through the spindle. I would like to try installing some sort of support inside the headstock so that when you pre-load the bearings, you are not just crushing the casting. Grizzly evens warns about not over-tightening the pre-load on the bearings as the casting can break. I believe like you nateman_doo that it is vibration being transferred through the machine.

  6. #6
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    Re: Grizzly G4003G Lathe

    I feel vibrating when I touch the machine. I would try rubber pads under the machine in the first place. I mean there is a LOT of gears in there, and perhaps they are just prone to rattle. Since I paid almost 4 THOUSAND dollars for the machine, I think it should give a decent finish. I didn't even think to contact Grizzly tech support. it can't be bearings, my machine has a few weeks of SUPER light use on it.

  7. #7
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    Re: Grizzly G4003G Lathe

    Quote Originally Posted by kae View Post
    It seems like it may be more than just an isolated case. I have been corresponding with a Grizzly Tech who said that I should try using rubber pads between the drive motor and the lathe. When I checked my lathe it has rubber pads from the factory. His next suggestion was to replace the headstock bearings. I have them ordered but I am not very hopeful that this will solve the problem. I am inclined to believe that it may be a combination of things. First, the headstock casting is very thin. There is not much metal around where the bearings are mounted. This could be part of the problem. Second, these bearings may not be designed for the type of loads that lathes are required to take. Third, the gears in the headstock may just impart some vibrations through the spindle. I would like to try installing some sort of support inside the headstock so that when you pre-load the bearings, you are not just crushing the casting. Grizzly evens warns about not over-tightening the pre-load on the bearings as the casting can break. I believe like you nateman_doo that it is vibration being transferred through the machine.
    Do you have the capabilities to put the machine on the concrete floor? Just to try it out and see if your table is the cause of the vibrations?

  8. #8
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    Re: Grizzly G4003G Lathe

    When I bought the machine, I purchased the cast pedestal stands. It is very securely mounted and leveled.

  9. #9
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    Re: Grizzly G4003G Lathe

    Here is a good picture of the harmonic finish.


    its actually quite pretty, albeit undesired. This is on the lowest possible cross slide travel. With the upper A gear as a 30T as opposed to the 60T. Its smooth has glass, but it still has that pattern on it. This material is delrin, with maybe a thousandth finish pass?

  10. #10
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    Re: Grizzly G4003G Lathe

    That looks familiar.

  11. #11
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    Re: Grizzly G4003G Lathe

    I have heard some owners claim to eliminate this issue by swapping out for a 3 phase motor and a VFD. Wiring one up correctly with the existing front panel controls is not a task to approach without some considerable fore-thought.

    Other owners have claimed partial success by putting some rubber matting between the motor and the mounting plate.
    Tim
    Tormach 1100-3, Grizzly G0709 lathe, Clausing 8520 mill, SolidWorks, HSMWorks.

  12. #12
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    Re: Grizzly G4003G Lathe

    My lathe came from the factory with rubber isolation pads between the motor and the mounting location. This was the first thing that the Grizzly Tech suggested. When this didn't work, he said the head-stock bearings were probably bad. I really don't think it is the bearings. Not enough hours on the lathe.

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    Re: Grizzly G4003G Lathe

    For those who have followed this thread, I made some progress today.The problem was a "harmonic" pattern on any turned surface. Changing feeds and speeds did not make any difference, the problem was always there. I determined that the problem was in the motor. I did this by a very simple test. I removed the drive belts, left the motor turned off and had a friend drive the gearbox pulley with a hand drill while I took a light cut. The result was a perfect finish. To further test my theory, I then started the motor but still drove the gearbox pulley with the hand drill. The result was a return to the harmonic pattern. Vibrations from the motor were being transferred into the headstock because of the metal to metal mounting. At this point, I knew the problem was in the motor. The next day I stopped by a local motor shop and explained my problem. They told me that they saw this problem quite often in Chinese motors. He told me that he found that if he took the motor and re-dipped and baked the stator, many times the problem went away. They had found that the laminated metal sheets that comprise the stator weren't tightly bound together and they created a resonance. He said he could re-work my motor for $50. I asked if he guaranteed it would work and he said no but he felt 95% sure it would solve the problem. I dropped off the motor, he performed the process and I picked it up yesterday. However, when I picked it up, he said he doubted if this would work because it still had the same buzz in it as before he dipped it. He did offer one piece of advice and that was to try to use a vibration damping motor mount. He said they were available from McMaster-Carr. I paid the $50 bucks, came home and found the item at McMaster and ordered four of them at about $3 each. I was hoping to salvage the $50 already spent. They arrived today and I mounted them with the motor and I am happy to say that about 90% of the "harmonic" pattern is gone. I suspect that the remaining resonance is coming through the drive belts. The only other solution is a new motor. For now, I am satisfied with the quality of finish. It is many times better than before. The McMaster part number is 9217K49. There are a number of choices for compression load, shear load and bolt size. The way my motor mounts, shear is the main concern as was the 8mm bolt size. The reason that rubber pads did not work was that the bolts still transferred the vibration into the headstock. The vibration damping mounts I refer to does not have a bolt that goes through the rubber. The studs are isolated from each other by the rubber mount. If you go to the McMaster web-site, you will see what I mean.

  14. #14
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    Re: Grizzly G4003G Lathe

    Can we see some pictures of the job?

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    Re: Grizzly G4003G Lathe

    I don't have any before and after photos of the improved finish but I took a couple of the vibration isolation mounts. As I mentioned, there is still a slight amount of harmonic but it is greatly improved (actually quite hard to see without a 10x loupe). I feel that the remainder of the harmonic pattern is coming through the drive belts.
    Attached Thumbnails Attached Thumbnails Vibration Isolation Mount_0122.jpg   Vibration Isolation Mount_0124.jpg  

  16. #16
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    Re: Grizzly G4003G Lathe

    The key to this is that the bolts that attach the motor do not pass through the rubber. That is why rubber pads between the motor base and the motor mount did not work. The vibration was still being transferred through the bolts. I forwarded this info to the Grizzly Tech I had spoken to and he first apologized for the problem and then said he would pass the info on to the quality control department. Don't hold your breath but it is a step in the right direction. As for the remaining harmonic pattern, it would probably require the purchase of a new motor. For now, I am pleased with the results.

  17. #17
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    Re: Grizzly G4003G Lathe

    But the McMaster mounts you used work much better then stock?

  18. #18
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    Re: Grizzly G4003G Lathe

    nateman_doo, the rubber pads that came with my lathe from the factory did not work at all. The reason being was that the bolts that held the motor to the lathe passed through a hole in the rubber pad. This allowed the vibration from the motor to simply pass through. Yes, the McMaster-Carr isolation dampers have improved the situation by 90%. I feel that the remaining vibration is being passed through the drive belts. Go to the McMaster Carr web site, type in the part number I posted, and you will see that the mounting studs are on each end of a rubber cylinder, it does not pass through.

  19. #19
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    Re: Grizzly G4003G Lathe

    I just ordered them. No idea when i will get to the install of them, but I will take your word for it.

  20. #20
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    Re: Grizzly G4003G Lathe

    I hope it works for you like it has for me.

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