G4003g Motor Vibration Surface Finish Issues Fixed!!

coolidge

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Issue: The surface finish when the lathe was new was pretty decent, but quickly deteriorated as the lathe broke in to the point that this is what it looked like after about 15 hours run time. Yikes, this was at 70 rpm about .002 per revolution. It was less severe at 220 rpm but still very poor, mediocre at 320 rpm, not bad at 800 rpm at the finest feed .001 per revolution but even then still had spiraling showing up in the surface finish. Facing also had this spiraling showing up in the surface finish.

There are numerous reports from G4003G owners regarding this issue, some reporting its an issue with the motor and suggested replacing the motor, others reporting that isolating the motor from the lathe improved or resolved the issue.



My take on this after methodical step by step testing is, this is the result of a combination of issues.

1. Poor motor mount design. The factory motor is mounted directly on the lathe bed casting, metal to metal which transmits buzz and hum from the motor directly into the lathe. You can feel this with your hand everywhere on the lathe, headstock, chuck, tailstock. Its accurate to describe it as a buzzing humming type vibration. This is with the belts removed, just the motor spinning in mid air. You can measure this with a .0001 indicator on the chuck and watch the needle buzz back and forth .0001 to .0002 with an occasional spike. So its not the V belts (though using a link belt does reduce V belt vibration).

2. The factory motor itself did develop a WHA WHA WHA Wooo harmonic which was a contributing factor but primarily it was the buzz/hum into the lathe causing the problem.

3. Since the lathe initially didn't exhibit this problem my theory is when the headstock was brand new and tight it was able to deal with this motor buzz. But as the headstock broke in and loosened up it became susceptible.

I decided to replace the factory motor to test some peoples theory that it was just the motor that was the problem. This was not the case.



As you can see I did make half an attempt to isolate the motor but there was still some metal to metal contact between the motor and the lathe via the edge of the bolt and again you could feel the whole lathe buzzing/humming from headstock to tailstock even with the Baldor Motor. While this did get rid of the WHA WHA WHA Wooo issue on the factory motor, the Baldor spinning true and even, mostly the surface finish issue remained.



Here's the test I ran after installing the Baldor motor with the above rubber washers. From right to left I turned 3 sections, at 70 rpm, 220 rpm, and 320 rpm. While the surface finish/spiraling issue was reduced, it remained.



So I ordered some real isolation mounts from McMastercarr. These completely isolate the motor from the lathe, there is no metal to metal contact.



Here you see them installed. This is not ideal as the motor mounts on the lathe sideways putting a shear force on the isolation mounts. They are rated for 20lbs shear but distort a bit and there is some motor vibration, ideally I would redesign the motor mount so that the motor sits flat down on the isolation mounts like in this photo.



Drum roll...with these isolation mounts installed the surface finish issues were eliminated! So was the buzz/hum in the lathe. With just the motor running before installing the belts there was zero buzz/hum and just the very slightest occasional something which was the motor wiggling a bit on these rubber isolation mounts, it was like night and day. So I installed the link belt and even with everything spinning, belt, spindle, quick change gears, carriage feeding turning the OD the lathe felt quiet if you place your hand on it, you could feel something with all that stuff rotating but the best way I could describe it is it felt quiet.

Here's the same test as above, 70 rpm, 220 rpm, 320 rpm, same tool same feed, you can't really tell any difference except for the two lines separating the three turns where I turned off the lathe to change spindle speeds.



And here's a face cut wow, and this is magnified about 4x, no spiral patterns at all.
 
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Do you have a part number for those mounts?

I have a vibration problem on my lathe also and I'm going to have my splash guard off installing my DRO, so perfect time to see if the mounts would help.
 
Part # 9376K42

They come in many different sizes and styles on McMasterCarr search "vibration damping sandwich mounts"
 
Thanks. That gives me a starting point to find what I'll need.

Looks like the mounts raised the motor up about 1" from the pics. I'll probably have to buy a new pair of belts, but if it cuts down on vibration it's worth it.
 
awesome news. Those are the same sound mounts that I put on my G0709 as well. Just still using the stock motor. It will go one of these days.

So is this going to change your mind about trading up to a larger lathe?

I have read a few dozen posts over the years of people gusking about what a big difference it made to swap out the cheap chinese motor for a three phase motor. You are the first one to demonstrate the difference between a quality one phase and a cheap one phase motor. Definitely is a much simpler conversion. Guess I need to go shopping for a new motor...

Thanks for the before and after product pictures. That shows an amazing difference. You should email those to Grizzly customer service.... not that I would it expect it to make a difference.
 
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i think someone missed the hole story it was not the motor is was the vibration dampening
 
I had previously read about this by other G4003G owners, they tried all sorts of things. It was one of the reasons I started looking at other lathes after reading some of the G4003G owners frustrations on this issue, and in some case it was never resolved. They sold their problem to someone else. Real makes you wonder about process improvement, or just plain company ignorance. Informative photos real tell the story, job well done.

Long term using those motor isolation mounts, you may have some issues with sagging or twisting. I assume the motor needs to be mounted in the vertical plane because of clearance issues when using single phase motors.
 
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