# G4003G shaking/vibrations



## Shawn_Laughlin (Feb 11, 2020)

From 270 to 1400 rpm my machine shakes like there is something out of balance or round somewhere in the drivetrain or spindle. It can be seen with the naked eye if you look at say the tip of the live center while mounted and while machine running. The spindle seems to be good as checked with my dti so, I don’t think it’s that. It does it no matter if back gears are engaged or not but I do see some wobble in the lowest gear and it binds a bit when I rotate by hand in one spot so I know it’s out of round but like I said it does this no matter if gears are engaged or not.

So my fix was to use the threaded holes on the rear of shaft for spider studs,I believe they are called, and started by moving one out,locking it down and them turning on the machine and adjusted as seemed fit. Picture below is showing what I did but, not sure if this could cause problems down the road? I don’t see why it would since it cleared up a noticeable amount of the shaking but I would like some experienced guys to comment on it please? Also when I’m auto feeding in the x and Watching the hand wheel it like pauses for a split second but it’s randomn and not at the same spot in rotation. What could cause that? Thanks


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## cbellanca (Feb 11, 2020)

It looks like you deffinately have something out of balance or not properly alligned. The gears bore could be off center. I would check runout. Apply bluing to the gear teeth to check for excessive contact.  Check the gears pitch diameter. Have the gears balance  checked .


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## derfatdutchman (Feb 12, 2020)

I agree something is out of balanced,  not aligned or loose. Along with checking the gears, and pullies, check to make sure all the fasteners in the drive train & motor are tight.


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## DavidR8 (Feb 12, 2020)

Maybe this is implied in your post but is there runout when the spindle is isolated from the drivetrain and turned by hand?

Can you isolate the spindle from the rest of the drivetrain? 
Meaning start with running the motor alone, make sure there’s no imbalance there. 

Then add in the next part of the drivetrain and see what happens. 


Sent from my iPhone using Tapatalk


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## Superburban (Feb 12, 2020)

I would definitely take the cover off, and check for any play in any of the shafts. Any binding felt by hand turning the chuck, is bad.

PS. The G4003G does not have a back gear.


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## fitterman1 (Feb 13, 2020)

Try getting rid of those drive belts, I use them on tractors but not on machinetools


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## higgite (Feb 13, 2020)

Shawn,

Hi, time warp neighbor. I lived in the Groves and PA and across the bridge in BC for a few years back in the ’60s-’70s.

I can’t help you with the vibration, but the pause in the carriage handle when auto feeding is likely due to the combination of backlash in the carriage gearing, gravity pulling on the wheel handle and friction in the system. When the handle comes over the top, gravity does its thing and the handle “outruns” the backlash. Then when it passes the bottom of its rotation, gravity does its thing again and the wheel will pause until the backlash is taken up again. Friction influences where in the rotation it happens. At least that’s what happens with my lathe. I suspect it’s a common occurrence on other lathes, too. You can test it by holding slight pressure on the handle while it goes through a revolution and see if you feel a pause or not.

Tom


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## epanzella (Apr 11, 2020)

Those spider bolts make a difference in vibration with the lathe turning 270 RPM? Something eles is going on. Take the sipder bolts right out. Disengage the feed gear train. Put the head stock gear shifter between positions so you can rotate the spindle by hand.  Something could be binding or it may just be you bases are not sitting flat on the floor and a slight imbalance is rocking the boat. That machine is in the neighborhood of a thousand pounds and the position of a 2 ounce bolt should not make any noticable difference.


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## petertha (Apr 11, 2020)

When I replaced the Vee belt on my 14x40 I noticed some harmonic vibration at certain rpms that was never there before. It ended up being the hinge plate motor mount. Most Asian lathes like this have a kind of rudimentary jack screw through the plate. I assumed it was to pull a but of tension on the belt. But the trick is to lock it down so it doesn't float & start a resonance. That solved all the vibration issues.


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