Improving rigidity and surface finish on the G4003 lathe

[jgedde]

At one point I mentioned parenthetically that my G4003 headstock was braced to the wall of my shop and a quick and dirty motor mod that improved SF. I was asked in a PM to provide pictures. So here's some pics with a brief write-up.

First the motor mod. A single phase motor inherently vibrates at some multiple of the mains frequency. This vibration can be felt all over the lathe and shows up in the SF. So, the first and most obvious fix would be to mount the motor on isolators which I did. It made things better but did not eradicate the issue. I found that loosening the belt tensioning bolts so the motor can float a bit, then supporting the motor from underneath would allow said vibrations to go into the stand rather than the lathe itself. So, I just cut a 2x4 about 8" long and sanded a small taper on it. By driving like a wedge between the lathe and the stand, I found a sweet spot where vibration almost completely went away.

Here's a photo of the isolators and the wood:


Next, I wanted to improve the rigidity of the headstock by bracing it to the wall. This was the most bang for the buck. Since the back edge of my lathe stand is tied to the concrete wall of my shop, this works for me. If your stand is not tied to the wall, or your walls aren't concrete, you're likely to make things worse by doing this... My lathe stand is multiple layers of plywood with a metal and wood subframe. I could park a tractor on it!

The photos will say it all. The groove in the right side of the brace allows the cover on the electrical box to open.



John

 

[Ray C]

John,

Something seems wrong here... A G4003 is a fairly substantial lathe with enough mass to dampen most of it's own vibrations. You might want to look for other sources of problems such as the bench, the balance of the chucks and the main sheave off the drive belts. Could even be an out of balance motor... Basically, any gear or rotating object more than a few inches in diameter can muster-up enough momentum to shake a lathe so, checking all those things and tuning them might help.

Chucks are usually the biggest problem. Have you tried running at all speeds w/o a chuck? Most often, vibrations come and go at different speeds. If it is the chuck, I have several threads here on how to improve the balance of chucks.

It's been my observation that single phase motors create a vibration that's usually seen when facing a piece but not so much when doing a normal surface cut. My lathe is basically the same as yours and even when it was on the stock factory metal bench, it ran very smoothly. Yours should do fine too and there's no reason you should have to go through these hassles. It's very annoying and takes your mind off your work...

EDIT:
Also, I'd be inclined not to bolt the head to an external structure. When a lathe is aligned properly, it relies on being bolted at it's base points and I could envision how an external brace might upset that apple cart.

Also, try running the motor free-standing to see if it vibrates.



Ray

 

[drs23]

At one point I mentioned parenthetically that my G4003 headstock was braced to the wall of my shop and a quick and dirty motor mod that improved SF. I was asked in a PM to provide pictures. So here's some pics with a brief write-up.

First the motor mod. A single phase motor inherently vibrates at some multiple of the mains frequency. This vibration can be felt all over the lathe and shows up in the SF. So, the first and most obvious fix would be to mount the motor on isolators which I did. It made things better but did not eradicate the issue. I found that loosening the belt tensioning bolts so the motor can float a bit, then supporting the motor from underneath would allow said vibrations to go into the stand rather than the lathe itself. So, I just cut a 2x4 about 8" long and sanded a small taper on it. By driving like a wedge between the lathe and the stand, I found a sweet spot where vibration almost completely went away.

John

Thanks for the photos. I was able to get my 4003 G to completely settle down by adding 4 more anchors to the floor. I originally had two, one on either end and figured that was fine. When it still vibrated a little and I could induce a slight rocking motion by shaking the headstock I knew it needed a little more. The additional anchors did the trick.

Thanks for the photos.

Dale

 

[jgedde]

John,

Something seems wrong here... A G4003 is a fairly substantial lathe with enough mass to dampen most of it's own vibrations. You might want to look for other sources of problems such as the bench, the balance of the chucks and the main sheave off the drive belts. Could even be an out of balance motor... Basically, any gear or rotating object more than a few inches in diameter can muster-up enough momentum to shake a lathe so, checking all those things and tuning them might help.

Chucks are usually the biggest problem. Have you tried running at all speeds w/o a chuck? Most often, vibrations come and go at different speeds. If it is the chuck, I have several threads here on how to improve the balance of chucks.

It's been my observation that single phase motors create a vibration that's usually seen when facing a piece but not so much when doing a normal surface cut. My lathe is basically the same as yours and even when it was on the stock factory metal bench, it ran very smoothly. Yours should do fine too and there's no reason you should have to go through these hassles. It's very annoying and takes your mind off your work...

EDIT:
Also, I'd be inclined not to bolt the head to an external structure. When a lathe is aligned properly, it relies on being bolted at it's base points and I could envision how an external brace might upset that apple cart.

Also, try running the motor free-standing to see if it vibrates.

Ray

Thanks for the input. I thought of all that stuff two years ago when I did this. The headstock alignment doesn't seem to be affected by the brace as it is mounted using a single point - think a hinge - with a substantial clearance hole to allow for some movement before cinching it down.

There is no question something is out of balance somewhere - likely my three jaw chuck and the motor. Nonetheless, I now get a SF that rivals that obtained using the Monarch 10EE's I used to use. You're right about the brace vs the stand. My stand is NOT bolted to the floor - by design. Mine is bolted to the wall behind it and the front legs function as levelers. Of course this required the back mount be inherently level which it is. 0.0015 per foot. But, the stand was a quick and dirty setup and could have been better (and more $$$). The good news is that the stand is excellent at dampening vibrations that get into it.

My lathes motor does vibrate quite a bit - much more so than the same motor that's used on my milling machine. At some point, I'll likely convert it to 3-phase with a VFD for the untimate in smooth running.

But, then again. My old job has a 10EE that needs a new transformer. As far as I can tell, they have no plans to fix it. They guys there know I'd buy it if they decide to get rid of it. If that happens, the Grizzly would be sold.

All in all, you're right. I should not have had to do these Band-Aids, but it works for me and has been set up that way for two years. Again, I only posted this by request and your milage may vary.

John

 

[Ray C]

Gotcha... If you're happy and the machine cuts the way you want it, that's all that counts! Didn't mean to interfere but was offering some suggestions. It was not meant in any negative way.


Ray

 

[The Liberal Arts Garage]

RRe: Improving rigidity and surface finish on G 4003 lathe"

At one point I mentioned parenthetically that my G4003 headstock was braced to the wall of my shop and a quick and dirty motor mod that improved SF. I was asked in a PM to provide pictures. So here's some pics with a brief write-up.

First the motor mod. A single phase motor inherently vibrates at some multiple of the mains frequency. This vibration can be felt all over the lathe and shows up in the SF. So, the first and most obvious fix would be to mount the motor on isolators which I did. It made things better but did not eradicate the issue. I found that loosening the belt tensioning bolts so the motor can float a bit, then supporting the motor from underneath would allow said vibrations to go into the stand rather than the lathe itself. So, I just cut a 2x4 about 8" long and sanded a small taper on it. By driving like a wedge between the lathe and the stand, I found a sweet spot where vibration almost completely went away.

Here's a photo of the isolators and the wood:
View attachment 57494

Next, I wanted to improve the rigidity of the headstock by bracing it to the wall. This was the most bang for the buck. Since the back edge of my lathe stand is tied to the concrete wall of my shop, this works for me. If your stand is not tied to the wall, or your walls aren't concrete, you're likely to make things worse by doing this... My lathe stand is multiple layers of plywood with a metal and wood subframe. I could park a tractor on it!

The photos will say it all. The groove in the right side of the brace allows the cover on the electrical box to open.

View attachment 57495

John

This successful bit of observational engineering reminds me of my(some time ago) suggestion
that someone with a taste for analytical vibration observation might think about a simple hand
held detector / probe to out put to a typical computer a graphical line to show ,coarsely, contact
frequency and amplitude - maybe 20 to 7000 Hz ? Just a little challenge...BLJHB