Grizzly G0766 vibration issue. If you have this lathe, please comment

[dustin wassner]

I just finished setting up the new machine.

I am getting a notable vibration in a very specific rpm range (rather a frequency range) on both the high and low range. Literally, just below 950 rpm and it is smooth as glass, as well as just above 1100. Between these it is terrible. I don't remember the specific rpm range for low speed.

I tried running the motor without the belt and there was no vibration. I am not measuring any runout anywhere, and don't believe this is a matter of something being out of balance.

I think it may be an issue with the 3 phase motor when under load. I built a lathe this past year and had the identical issue, where I would run the motor between 43 and 49 hz and the motor itself would vibrate, almost like the VFD was causing some kind of weird resonant frequency pulsation as it was converting the DC into AC. I know that resonant frequencies deal with sound, but whatever the "resonant frequency" equivalent is for electrical stuff, I think I may be experiencing it. Not really sure, but it seems like way too tight a range to be a mechanical out-of-balance issue...

Either way, has anyone else who owns this machine found this to be an issue?

I plan on contacting grizzly monday. I do hope they can offer assistance...

[Roger Chandler]

Make sure youhave gone through the lathe and tightened all the screws, especially the pulley set screws on the spindle and motor shafts. Make sure the clamp plate is seating tight underneath the bed ways.....sometimes as little as a half turn of the nut can make a difference in vibration. Inspect the belt and pulleys to make sure there is not a place on the belt ribs that has a buildup of debris on it.
My G0766 runs smooth as silk, but the first thing I did when uncrating and assembling was to go through the entire lathe and tighten every screw, bolt, nut and get everything dialed in.

There is also a spindle spacer next to the pulleys and it has a step in one side that fits into the side of the pulley, and it needs to be snug into the pulley, and locked down with the set screw, so check that as well.

[dustin wassner]

I just gave the entire thing another once-over. Everything looks great.

I just rechecked the rpm range of vibration. It is exactly the same on both the high and low range, so it is NOT occurring at the same frequency...

I am encouraged that yours runs smooth at all rpm's. I am confident that Grizzly will help me with this.

thanks for the input Roger.

[Bill Jobe]

That problem seems very unusual.

[Roger Chandler]

I recommend you call Grizzly tech support, and let them walk you thru the issue to troubleshoot......they may decide to send out a new part, or something.

[Steve Schlumpf]

Make sure you have the bed of the lathe level; left to right, front to back. You would be amazed at what happens when the bed has a very slight twist.

[Roger Chandler]

Make sure you have the bed of the lathe level; left to right, front to back. You would be amazed at what happens when the bed has a very slight twist.

I actually thought about the same thing last night right before bed, so I'm glad you mentioned this Steve. Harmonics on a lathe get magnified from the seemingly most insignificant things. Also, what may not show up on a midi lathe or smaller lathe will show up on a larger lathe because it has such a larger frame, and what is just a small amount of twist is magnified much more with a long bed and much more cast iron or steel.

[Roger Chandler]

I just gave the entire thing another once-over. Everything looks great.

I just rechecked the rpm range of vibration. It is exactly the same on both the high and low range, so it is NOT occurring at the same frequency...

I am encouraged that yours runs smooth at all rpm's. I am confident that Grizzly will help me with this.

thanks for the input Roger.

It showing up on both high and low range makes perfect sense, in that the pulleys are cast together, and are not separate individual pulleys. That means that if there is a something in a particular spot on the rotation, then it will show up on either belt setting, however, it would seem it would also show up at any rpm. Make sure that bed is level, as mentioned in my reply to Steve.

Know this, Dustin....that the great majority of issues people have had with the G0766 when they initially got it was due to setup issues. You can read threads on the GGMG, and see where we've dealt with bed leveling and vibrations, etc. Even, the weight distribution on the legs can affect harmonics. If one of your feet pads is not carrying approximately the same load as the other feet, it can make the harmonics do strange things. Most of the time it is something related to the users setup...........that being said,

If there is something about your machine, Grizzly will make it right. Not sure how much experience you have with lathes, but just trying to be helpful here......the Grizzly Green Monster Group [GGMG] was started by me back in 2010 or 2011 just to give owners a place to bounce things off one another and be a support group, and there is a lot of knowledge there about these lathes, so feel free to join! :)

[Gary Hague]

I had the exact same issue when I first set up my G0766, vibration in that same speed range only. Carefully leveling the lathe fixed the problem. Hope it works for you.

[David C. Roseman]

[snip}
I just rechecked the rpm range of vibration. It is exactly the same on both the high and low range, so it is NOT occurring at the same frequency...

[snip]

Dustin, a couple of thoughts in addition to the good advice Roger and others have given.

First, perhaps I'm misunderstanding, but I'm puzzled by your comment about frequency. If the vibration is occurring at the same rpm in both high and low range, then isn't it, in fact, occurring at the same frequency output of the VFD? Changing between high and low range simply changes the gear ratio mechanically by moving the belt. No? The digital readout on the headstock's display shows only rpm. So I gather you mean that the vibration is occurring at the same rpm readout, regardless of the belt being in high or low range.

To see the frequency output, you'd need to pull the steel dust cover on the Delta VFD.

Second, is the vibration that you are noticing accompanied by a change in the sound coming from the motor, specifically a high-pitched trill? Or is it simply a vibration (rapid shake)?

Congratulations on the new lathe!

[dustin wassner]

David,

Thanks for the response. The vibration is occurring at the same rpm range, but to obtain this same range on either the high or low would require a different frequency. The potentiometer knob is in a completely different place to achieve the vibrating rpm in high vs low range.

The motor does make a high pitched noise that changes throughout the frequency range, as did the lathe that I built. I found that on my old lathe, when I changed the carrier frequency in the vfd, it altered this electrical noise, and could be nearly eliminated if I were to max out the carrier frequency, but it would make the motor run hotter.

The vibration, as I can tell, has no correlation to the electrical noise, its just a rapid shake. But the problem is just so darn similar to the one I experienced before that it is hard to believe that it is not similar in cause.

DW

[Roger Chandler]

David,

Thanks for the response. The vibration is occurring at the same rpm range, but to obtain this same range on either the high or low would require a different frequency. The potentiometer knob is in a completely different place to achieve the vibrating rpm in high vs low range.

The motor does make a high pitched noise that changes throughout the frequency range, as did the lathe that I built. I found that on my old lathe, when I changed the carrier frequency in the vfd, it altered this electrical noise, and could be nearly eliminated if I were to max out the carrier frequency, but it would make the motor run hotter.

The vibration, as I can tell, has no correlation to the electrical noise, its just a rapid shake. But the problem is just so darn similar to the one I experienced before that it is hard to believe that it is not similar in cause.

DW

to obtain the same rpm range on different pulleys, it means you would have to change the potentiometer settings. This sounds like something with your setup, and not anything electrical with the lathe to me. That mechanical ratio of the pulleys are different and mean that to get to say 800 rpm on the low belt setting, your pot has to be at a higher place on the speed dial, and much lower on the dial if you use the high belt setting. The inverter/motor hum is normal and mine actually improved as the lathe broke in....some high pitched sound is normal, but vibrations at a certain rpm speed is likely to be something in the harmonics, which is probably in the bed being torqued, and load distribution to the feet not being fairly equal.

Having to reach the same rpm for this vibration to manifest itself whether on high or low belt settings tells us that there is not some issue with the spindle being bent, or some issue with the motor, as it seems to smooth out at higher and lower rpm's. This really does sound like harmonics, and you will have to trace that one down in your individual and unique shop setting. For example, if your floor is concrete and has lower places and higher places [as most concrete floors do] then the weight distribution on the foot pads could be an issue if one is in just a slight depression in the concrete.
You could try putting a small piece of rubber pad underneath each foot, and that may take away those vibrations. If you are on wooden floors, then a particular board, or floor joist may be 1/8" out of level, and that can affect the harmonics of the lathe......every shop is different and every turner needs to dial his setup in, so that it gets the best performance.

I refer you back to Gary's identical issue in his above post........likely you will have the same remedy!;)

[Reed Gray]

I was also going to suggest that having all 4 feet flat and even on the ground is often a culprit with this issue. Concrete floor is a must. Other than that, no real idea.

robo hippy

[John K Jordan]

I looks like that lathe is constructed much like certain Jet and Powermatic lathes.

If so, be be sure you have not over-tightened (or under-tightened) the belt. Many people push down on the lifting lever before locking and some have experienced damage from over-tightening. The PM 3520b instructions warn "do not overtension" and in places recommend to let just the weight of the motor provide the tension. The Jet 1642 manual states "Lower the tensioning handle so that the weightof the motor provides the needed tension and tighten the locking handle."

The 766 instructions say otherwise but they do provide a spec for belt deflection at the proper tension. (uncalibrated, of course)

Just something to check.

Also, for a clue you might use a stethoscope (or a big screwdriver with the handle to the ear) as you would in any machinery to try to pinpoint exactly where a sound/vibration is originating.

JKJ

[David C. Roseman]

David,

Thanks for the response. The vibration is occurring at the same rpm range, but to obtain this same range on either the high or low would require a different frequency. The potentiometer knob is in a completely different place to achieve the vibrating rpm in high vs low range.

The motor does make a high pitched noise that changes throughout the frequency range, as did the lathe that I built. I found that on my old lathe, when I changed the carrier frequency in the vfd, it altered this electrical noise, and could be nearly eliminated if I were to max out the carrier frequency, but it would make the motor run hotter.

The vibration, as I can tell, has no correlation to the electrical noise, its just a rapid shake. But the problem is just so darn similar to the one I experienced before that it is hard to believe that it is not similar in cause.

DW

Thanks, Dustin. Yep, if you're not detecting a correlation between the electronic motor noise and the vibration, then I think we can rule out that vibration is related to a VFD setting. So I agree with Roger and others that it's likely a harmonic vibration originating from a slight mechanical imbalance somewhere.

If, instead, the vibration correlated with that high-pitched, trill-like motor noise that changes with spindle rpm, I was going to suggest checking the pulse width modulation carrier frequency (parameter pr. 71) on the G0766's Delta Electronic VFD-M series motor drive. I've never heard of the pr. 71 setting being related to any vibration issue, but your experience with a similar vibration on your earlier home-built lathe traced to pulse width modulation made me curious about that. BTW, I'm not an electronics engineer, but I don't think you'd need to worry about overheating the motor if you were to max out the pulse width modulation setting by increasing the frequency on that particular drive. In fact, according to a Delta Electronics technical rep I checked with last year, the higher the setting the better the heat dissipation. Pr 71 of that inverter has a user-adjustable range of 1 - 15 (1kHz to 15kHz). The default setting is 15 when the unit leaves the Delta Electronics factory. Of the six G0766s I checked about a year ago, pr. 71 was set at 9, so I concluded that the factory in Asia that builds the G0766 to Grizzly's specs dials is back to 9. The lower the value, the more acoustic motor noise is noticeable, while the higher the value, the more electromagnetic interference may occur. Unless EMI is a particular concern, then dialing the setting back up to the Delta factory default should eliminate the trill if it is bothersome. Some folks find it so, others don't even notice it!

Grizzly locks out the onboard keypad on the VFD-M, presumably to discourage owners from fiddling with any of the 157 adjustable parameter settings and inadvertently creating problems. :) However, the keypad can be unlocked, and parameter changes made even without the keypad, by going in through the drive's telecommunications port with the correct interface and your laptop. The necessary software can be downloaded from Delta's website. Last year I put together a tutorial on this, as well as on adding an electronic braking resistor to the drive (it already has dedicated terminals for a braking resistor). I'll be happy to email you a copy if you'd like. Just PM me with your email address, as the file with pics is too large to post.

I think you're going to love that lathe once you sort out the vibration issue.

David

[dustin wassner]

Interesting. When I spoke with a technician at North American and Teco Westinghouse they both stated that the higher carrier frequency would cause the wingdings to run hotter.

Did you adjust the frequency on yours, and if so, how long have you been running it like this?

I will PM you. As a side story, my Teco VFD had an abundance of settings as well. One was deceleration rate. Being impatient, I turned it way down. I then finished truing the 24" mdf disc sander attachment I was making. I had never used the grub screw on a faceplate before... you may see where this is going. Lets just say that a disc that size at 1700 rpm that unthreads off the spindle comes alive when it hits the ground... I now use factory decel rates and grub screws...



I have the lathe on concrete, and although I do not yet have it anchored to the slab, after shimming, the bed is dead level. I used my Starrett machinists level and both ends of the bed are within .001 width-wise, along with levelness along the length. Vibration was still there at the exact same rpm range. However, what I did not notice before, is that the vibration returns around 2k rpm but not as strong, but is worth noting since it is double the lower rpm vibration.

[David C. Roseman]

Dustin, I've emailed the write-up to you. Yes, I adjusted the pulse width modulation carrier frequency on my G0766 two years ago, and on my G0733 four years ago (same series of inverter, but a different model to match the smaller 2 Hp motor on the G0733). No problems whatever since then. I also helped several other G0766 owners do the same about a year ago. The write-up discusses the various considerations involved.

I hear you about shortening the deceleration time too much on a VFD lathe! :eek: Sounds like your Teco may have an onboard braking resistor in order for it to stop so suddenly without going into "motor regeneration" and sending voltage back to the DC buss, causing the VFD to trip off for a few minutes to protect itself. On your Grizzly G0766, deceleration time is adjustable by changing the value of pr. 11. But if you want to shorten deceleration time, I recommend you first add a $40 Delta electronic braking resistor, especially if you intend to turn very, very heavy work pieces. If you are impatient about allowing the lathe to stop gradually each time you stop to check your work, you can inadvertently trip the VFD's internal breaker by trying to stop too quickly, e.g., by (1) toggling the directional switch to neutral instead of turning the potentiometer down slowly, or (2) by shortening the deceleration time by changing pr. 11 without adding the additional electronic braking. When the VFD trips off, inertia will cause the spindle to freewheel until it slows down by itself. That would make you more impatient. :) Adding a breaking resistor is easy, but involves some additional, simple parameter changes. That's covered in the write-up if you decide to do it.

[Brice Rogers]

I had some initial resonance points where I could feel some vibration. I think that some may be normal, but a lot is abnormal.
I initially leveled my lathe but there is another thing that I did. That was to make sure that the weight or force on each leg is roughly equal.
Here's how I did it. I raised the tailstock end off the ground from the top surface (engine hoist is best) and leveled the headstock end. So my lathe essentially had a 3 point stance - the definition of a plane. Then I l used a shim between the floor and the tailstock pads as a gauge to confirm that the tailstock pads were equidistant to the floor. Then I lowered the lathe. It helped a moderate amount. Lathe level and roughly equal weight on each leg.

[Brice Rogers]

Part 2 - - the next thing I did had more to do with off-balance pieces. I put a shelf across the lower portion of the legs and loaded it down with perhaps 300 or so pounds of sand. That also helped.

If your belt is irregular in some manner it could also be part of the problem. Irregular could mean mis-manufactured (like a lump or irregular thickness) or something as simple as not being lined up or being loose. Double check the alignment, remove the belt and examine it and try a different tension to see if it changes anything. Similarly, if the upper pulley (connected directly to the spindle) was mismachined and/or had runout, I think that it could also manifest itself with some resonance points.
When I first got my lathe it had some resonance points but having leveled it, balanced it, and weighted it, I don't notice them any more. Perhaps some minor irregularities of the belt, pulleys or something has broken in. Or I just am not paying attention to them any more.

[Roger Chandler]

[QUOTE=David C. Roseman;2762942 Yes, I adjusted the pulse width modulation carrier frequency on my G0766 two years ago, No problems whatever since then. I also helped several other G0766 owners do the same about a year ago.
[/QUOTE]
David.....now you have my interest peaked here. Exactly what does adjusting the pulse width modulation carrier frequency accomplish and what "problems" were you having that the adjustment addressed/eliminated? My G0766 seems fine with the factory settings, but if it could be tweaked even more to up the fine performance to an even higher level, then I'd jump on that! ;)

[David C. Roseman]

David.....now you have my interest peaked here. Exactly what does adjusting the pulse width modulation carrier frequency accomplish and what "problems" were you having that the adjustment addressed/eliminated? My G0766 seems fine with the factory settings, but if it could be tweaked even more to up the fine performance to an even higher level, then I'd jump on that! ;)


Roger, sorry, I should have been a bit clearer. When I said "no problems whatever since then", I meant no problems resulted from restoring the pulse width modulation carrier frequency setting to the Delta Electronic factory default value of 15kHz. The lathe shipped from Grizzly with a pr. 71 setting of 9kHz. The only reason I changed the setting in the first place was to get rid of some acoustic motor noise that presented as a high-pitched trill audible at certain rpms. The adjustment completely eliminated it. The trill doesn't affect performance at all. Many folks wouldn't mind it, and some, including two or three of my many friends who have G0766s, don't even notice it.

[Roger Chandler]

Roger, sorry, I should have been a bit clearer. When I said "no problems whatever since then", I meant no problems resulted from restoring the pulse width modulation carrier frequency setting to the Delta Electronic factory default value of 15kHz. The lathe shipped from Grizzly with a pr. 71 setting of 9kHz. The only reason I changed the setting in the first place was to get rid of some acoustic motor noise that presented as a high-pitched trill audible at certain rpms. The adjustment completely eliminated it. The trill doesn't affect performance at all. Many folks wouldn't mind it, and some, including two or three of my many friends who have G0766s, don't even notice it.

Thank you sir! Not a bad way to go, and I saved that .pdf you sent me on it last year or so ago. I might have to get you to stop by at some point [maybe the Symposium when you are in my neck of the woods] and help me adjust mine. The "trill" doesn't annoy me at all, so I guess it is no more than any of the 3520b's I've turned on, but I do have some hearing loss in the upper frequencies. I can hear it though when I use my lathe, but with the overhead air cleaner running and my Trend Airshield Pro on, the noises from those probably drown it out for the most part. You're a good man David, and thanks for all the help you give both here and on the GGMG!

[Joe Kaufman]

You might try with the headstock in the middle of the bed and then at the opposite end. Also try lifting each leg slightly with a large screwdriver while it is operating in the speed range of vibration. If you notice any change in amplitude, stop the lathe and place a putty knife blade under that foot. Restart the lathe and see if there is an improvement. If you are trying to take a slight natural twist out of the bed with the precision level process, that can contribute to the problem.

I have a PM3520B that has always (4+ years) had the vibration in that same high speed range. The motor, VFD, spindle bearings and belt have been changed for other reasons and the vibration remains.

[Brice Rogers]

Oh, a random thought or two:

One time I thought that I had a bad bearing knock. It turned out that I didn't have the headstock locked down. Embarrassing.

Dustin, I think that Joe had a good idea in regards to figuring out what is moving/vibrating. Besides checking the legs, like Joe mentioned, When you are feeling the vibration, put your finger along the seam between the headstock and lathe bed. Check if you can feel any movement, even if very slight between the two pieces.

Another thing to check might be the bearings. Put a dial indicator on the end of the spindle and tug the spindle to check if there is any looseness or conversely, rotate it by had to check if there is any "lumpiness" in the bearings.

[dustin wassner]

I have contacted Grizzly twice now about the issue and am still waiting to hear back.

The spindle turns easily and freely through its rotation. It has no runout and has no play moving forward and back.

I cleaned the underside of the headstock and after clamping it to the bed went along the entire area where the headstock and bed contact with a .0015 feeler gauge and could not slide it in anywhere.

I have tried moving the headstock to the far left and right on the bed and the middle and the issue does not change. This tells me that it is NOT a platform issue, since moving the headstock will considerably change the weight on each leg.

This morning I pulled the motor out and while holding it in my arms with the belt on its pulley and the spindle pulley I had my wife slowly turn the rpm up to the problem range. The vibration was not as much but was still there. That would eliminate the motor and its pulley from being the issue, so it must be either the headstock itself, the spindle, or its pulley.

Not sure if I mentioned this, but I put the grizzly faceplate on the spindle, and also tried my large cast iron oneway faceplate, and brought it up to the problem rpm range and the range not only was a little wider, but was considerably worse.

[dustin wassner]

After calling Grizzly a FOURTH time, I was told that the machine is within specification and that the vibration occurring is caused from the VFD.

I can send the machine it at my own expense and have it tested...

This is ridiculous.

[david privett]

I would find it hard to believe that a variance in the drive would cause any felt vibration, I would change out the bearings just cause sometimes they can fool you on what you would normally think. Mine had new koyo bearings made in Japan grizzly sent replacements that were made in China I installed them and it has been great since.

[david privett]

I just had a thought if the pot was not good it might made the drive search causing it to pulse and that would cause a perceived shake

[William McAnelly]

Could you see if someone near you has a 766 that you could try? maybe put your head stock on their lathe and use their motor to see if it is the problem.

[Brice Rogers]

When I first got my Griz 0766 it had some vibration. Not a lot but enough so I would adjust the speed control to either be above or below the resonance point.

Now my Griz is over 2 years old. It seems to be a lot smoother. I'm wondering if perhaps there is something like the drive belt having some stiffness, or being oval when relaxed, or something that has changed over time.

Just a thought....

Are there others who think that seem to think that their 0766 got smoother over time?

[Roger Chandler]

When I first got my Griz 0766 it had some vibration. Not a lot but enough so I would adjust the speed control to either be above or below the resonance point.

Now my Griz is over 2 years old. It seems to be a lot smoother. I'm wondering if perhaps there is something like the drive belt having some stiffness, or being oval when relaxed, or something that has changed over time.

Just a thought....

Are there others who think that seem to think that their 0766 got smoother over time?Good point Brice. Things, especially machinery alwys have a bit of a break in period. Cold winter weather could make the belt stiff as well, and cause some resonance. I know that my 0766 is smoother & quieter than when I uncrated it. I’m very happy with mine. I also went through my machine and tightened everything that could be tightened up before powering up the first time.

[Chris Hachet]

I have contacted Grizzly twice now about the issue and am still waiting to hear back.

The spindle turns easily and freely through its rotation. It has no runout and has no play moving forward and back.

I cleaned the underside of the headstock and after clamping it to the bed went along the entire area where the headstock and bed contact with a .0015 feeler gauge and could not slide it in anywhere.

I have tried moving the headstock to the far left and right on the bed and the middle and the issue does not change. This tells me that it is NOT a platform issue, since moving the headstock will considerably change the weight on each leg.

This morning I pulled the motor out and while holding it in my arms with the belt on its pulley and the spindle pulley I had my wife slowly turn the rpm up to the problem range. The vibration was not as much but was still there. That would eliminate the motor and its pulley from being the issue, so it must be either the headstock itself, the spindle, or its pulley.

Not sure if I mentioned this, but I put the grizzly faceplate on the spindle, and also tried my large cast iron oneway faceplate, and brought it up to the problem rpm range and the range not only was a little wider, but was considerably worse.

Wondering if you have an odd bearing issue.

[dustin wassner]

with smooth rotation of the spindle even by hand, zero runout, and zero end play, its highly unlikely.

A spindle for this costs $65. Grizzly probably pays less than $20 for it. Same situation with the bearings. They can't just send me a spindle / bearings / belt to see if that solves my issue?

Fact is I got a dud machine and Grizzly is not willing to help me.

[Roger Chandler]

You can purchase the belt online and bearings online for very little money. Belts from Vbelts.com or bearings from the big bearing store. Before I would take the spindle out of the headstock, I would try a new belt, and if that solved the problem, I'd call Grizzly back and tell them, then ask to speak to someone high up in the company, because if you have been getting the run around from tech support, then Shiraz Balolia needs to know about it. If it doesn't fix it, then perhaps talking to him by phone or email would be in order. My experience with tech support is mostly good, but I think sometimes they miss something in the communication, perhaps due to customers not being able to describe things correctly or inexperienced tech folks who just don't know. :confused:

You might be able to send Mr. Balolia a private message through this forum.....just an idea...

[Mark Greenbaum]

with smooth rotation of the spindle even by hand, zero runout, and zero end play, its highly unlikely.

A spindle for this costs $65. Grizzly probably pays less than $20 for it. Same situation with the bearings. They can't just send me a spindle / bearings / belt to see if that solves my issue?

Fact is I got a dud machine and Grizzly is not willing to help me.

Is it still under warranty? They sent me bearings and a spindle and touch-up paint both colors for free under warranty.

[Brice Rogers]

with smooth rotation of the spindle even by hand, zero runout, and zero end play, its highly unlikely.

A spindle for this costs $65. Grizzly probably pays less than $20 for it. Same situation with the bearings. They can't just send me a spindle / bearings / belt to see if that solves my issue?

Fact is I got a dud machine and Grizzly is not willing to help me.

Dustin, it is good that you measured end play and run out. I presume that you measured it at the working end of the spindle and applied some side or end pressure.

Another thought and something to eliminate: take a look at the pulley end of the spindle while it is under power. I notice on mine that the smaller upper pulley on mine has some runout - - perhaps 0.010 to 0.015 (just a guess). I didn't take the belt off so I can't speak to the larger upper pulley (low range). But if your pulley is not concentric, that could be a source of vibration or resonance.

It is unlikely that your spindle could lack concentricity based on how they are likely to machine it. But if you are up to it, take off the pulleys from the rear of the spindle and put a dial indicator on it while turning the spindle.

How bad is your vibration? Is there any way that you could quantify it?

[Dale Miner]

It sounds like a harmonic issue with the primary vibration frequency at the approx 950 rpm and a second harmonic at double the primary. (I did vibration analysis for a living in a previous life).

A minor amount of imbalance in the spindle excites the harmonic issue. If the problem was a gross imbalance in the spindle/pulley or an out of round pulley, the vibration would exist at all frequencies and worsen as the rpm's increased. If the problem was related to a defective belt the problem would exist at the belt frequency i.e. once per revolution of the belt. Changing ranges would change the belt frequency as it relates to the rpm of the spindle.


More than likely, even though the lathe is level , there is a difference in the weight on the feet side to side.

I am not familiar with the leveling system your machine uses, but if it has leveling screws back off one of the lock nuts on a back foot leveling screw and run the lathe at the speed where the vibration is the worst without anything mounted on the spindle. With the vibration occurring, try turning the leveling screws on the outboard end down. If no improvement or vibration worsens, turn the screw up. You should be able to find a spot that minimizes vibration by balancing the weight on both back feet. With the weight even on both back feet, the weight will also be properly distributed on the front feet.

I have had a PM 3520b and now have a OW 2436. On both of those machines I used/use the 'adjust back foot leveling screw' method to reduce vibration. Also have a Monarch engine lathe that weighs 6000# and has 8 feet. That machine takes the better part of a full day and a torque wrench to properly level.

[Roger Chandler]

Excellent information, Dale! Thanks for sharing it with us! The leveling system is pretty much like the 3520b on the G0766.

[John K Jordan]

.. The leveling system is pretty much like the 3520b on the G0766.

(Sorry if this has been checked and I missed it. This is a long thread.)

Before experimenting with the leg loading, I suggest testing for twist in the lathe by checking the alignment of the headstock and tailstock. Correcting twist with the leg levelers can equalize stress in the bed casting caused by even slight unevenness in the floor or improper leveler adjustment. The entire cast iron/steel bed can easily flex and twist significantly. Checking for and adjusting for this is the FIRST thing I do when moving a lathe, even if a short distance. I want the alignment perfect on my lathes.

If you look up "wood lathe tailstock alignment" you will find all sorts of things recommended including adding shims and pressing on the tailstock while tightening. I actually shimmed the tailstock on my first Jet 1642 before I found out about the simple leg adjustment technique.

The procedure, very quick. Put a drive center with a point in the headstock. Put a live center (or even another drive center with a point) in the tailstock and slide the tailstock until it the points almost touch. If the two points are in perfect alignment, good.

If the points are in horizontal alignment when looking straight down but out of vertical alignment when looking from the side, this is bad. I have not yet seen this on any of the lathes I've checked.

If the points are OUT of alignment horizontally, a common issue, the fix is usually easy.
If the tailstock point is too far towards you, twist the bed back into alignment by raising an appropriate leg - the easiest is the front leg on the tailstock end of the lathe. Untwist the bed by cranking UP a bit on the adjuster or with a shim under the leg. This should pull the two points into perfect alignment.
If the tailstock point is too far towards the far side of the lathe, adjust either the far right or front left leg.
I have had to do this on both of my Jet 1642s and my Powermatic 3520b after moving them. Each time it brought the lathe back into alignment.


A recent case: When turner Mark StLeger was doing an all-day demo at the Knoxville club last April he noticed the tailstock and headstock were out of alignment on the club's Jet 1642. This was a problem for a precise operation he was planning. I opened my big mouth and said I could fix it. During a break a few seconds of leg adjustment put the tailstock into perfect alignment. Whew! Actually, I wasn't worried since I had aligned that same lathe the same way several times in the past since it gets moved around a lot.

When I'm demoing something that can benefit from the tailstock alignment I always check the lathe and align it before I start. Such alignment is as not critical for spindles between centers but it can cause all kinds of issues when using the tailstock close to the headstock, such as when working on turned boxes, vessels, platters and bowls, or with thin spindles held tightly on the drive end and with the tailstock on the other end. Problems from alignment can be worse with hard, dry woods.

I don't know if this alignment will have any affect on the vibration issue in this thread, but I would check it first.

BTW, leveling the lathe (or table saw, etc) to the earth's gravity is nice but usually not necessary. What IS necessary is that the bed of the lathe or the table of the saw be in a perfect plane. A twisted bed or frame can cause a variety of problems. IMHO. Now for a billiards table...

JKJ

[dustin wassner]

funny you mention billiard table, as this is the very reason I bought the machinist's level. I was able to shim a 1917 full size brunswick to less than .003" on the entire playing surface. 1" slate.

As I had mentioned before, the vibration was at the same rpm when the lathe sat on the concrete unbolted and unshimmed and more than likely twisted. It vibrated at the same rpm after shimming and bolting it to the floor, and it vibrates despite where I have the headstock on the bed. In each state, the weight per leg varies considerably, so I see no correlation to the platform of the machine and the vibration.

[Dale Miner]

funny you mention billiard table, as this is the very reason I bought the machinist's level. I was able to shim a 1917 full size brunswick to less than .003" on the entire playing surface. 1" slate.

As I had mentioned before, the vibration was at the same rpm when the lathe sat on the concrete unbolted and unshimmed and more than likely twisted. It vibrated at the same rpm after shimming and bolting it to the floor, and it vibrates despite where I have the headstock on the bed. In each state, the weight per leg varies considerably, so I see no correlation to the platform of the machine and the vibration.

If I understand correctly, you now have the lathe bolted to the concrete floor? When making my suggestion about tweaking the weight on each foot that detail was not understood.

If the lathe is bolted down to the floor shimmed and leveled and a harmonic vibration presents itself, the problem exists elsewhere.

You might take the headstock off and see it the mating surfaces between headstock and lathe bed are providing a solid fit.

If there is a good solid fit, try running the lathe slowly with the headstock clamps loose and slowly bring the rpms up. If the headstock vibrates at all rpm's and the vibration gets expontially worse as the speed increases, there is an exciting force issue in the headstock.

If vibration is low until the 950 rpm range is reached, then likely the either the headstock or bed has a natural frequency at the 950 rpm that is excited by a slight imbalance or pulley runout in the spindle assembly.

Curious if you have tried running the lathe with the belt very loose? It is possible the pulley has radial run out that is exciting the natural frequency. Radial run out in the pulley would have a reduced tendency to cause a once per revolution vibration problem with a loose belt. Since you have a machinists level let me ask if you have a dial indicator and a way to measure radial run out of the pulley?

[Roger Chandler]

Dustin, I am in the process of reaaranging my entire shop to accomodate a second large lathe. In moving my G0766 from one side of the shop to the other side, my floor required me to make some changes. At the new location, my centers were a bit out of alignment, and the slope of my floor on that end of the building is noticable, so I had to do a complete re-level of my lathe. Even then, due to the floor, I had a bit of a front to back wobble on the tailstock end, that no matter how I adjusted the foot pads, would not exactly align my centers, meaning there was some torque in the bed ways.

Due to this, I decided to cut a 3”x3” square from a spare piece of anti fatique mat, and put it underneath the front foot pad on the tailstock end. That one small shim out of rubber brought my centers into perfect alignment, and eliminated any wobble and all vibration.

In one of my earlier posts, I recommended trying a piece of rubber underneath the foot pads, as they can change the harmonics when nothing else seems to solve the issue. I have an observation from years of hearing these types of problems....99% + of the time it is not the lathe, it is the conditions in which the lathe is setup, and in my humble opinion, the fact that you have the lathe bolted down might be part of the issue, since it is bolted down with the problem not eliminated, which simply locks in the problem.

I would also encourage you to back the bolts off that tighten the bed to the legs about 3 or 4 turns, let the thing settle with the weight of the headstock/banjo/and tailstock on its bed, and find a balance on it’s own with the legs unbolted from the floor. This will release any tension in the lathe, and it may eliminate the vibration. Bolted together parts, that have torque/tension in them will produce harmonics.....these steps and the rubber shims should dial this G0766 in for you.
Of course, re-tighten the leg bolts.

I hope you don’t feel like this is all too much of a pain, and please know many of us here are sincerely trying to help with our suggestions. I just have this gut feeling that there is tension somewhere in your setup that is causing this vibration and it can be eliminated. Of course, there is that very rare occurance where something may be amiss with the machine, so if that is what you find after trying these corrective measures, then you are in that less than .1% and have a legitimate case for a return of the lathe.

I hope you will try these steps and find what most of us already have found with our G0766 lathes....that they are fine performing lathes with great value for the size/features they offer. Best of luck as you troubleshoot this problem.....we are all hoping for the best for you! :)

[tom lucas]

Dustin, did you ever get this resolved?

[Roger Chandler]

Dustin, did you ever get this resolved?Tom, I hope you read the entirety of the thread here and not just the problem experienced by the poster. The G0766 is a fine lathe, and if you were to experience any issues, we are here to help in the GGMG. As mentioned, 99% + are problems in the individual setups and not with the lathe. Unless there is something amiss in the machining on a particular unit, the issues can be solved. Keep us up to date once you get your G0766 in your shop.

[Alex Zeller]

Now that it's a year older hopefully he got it resolved. If not (seeing he was able to measure the run out on the lathe) I would suggest doing the same on the tachometer pulley. With the belt cover off I think you should be able to find a spot.

[Thomas Wilson80]

Also curious if the OP ever resolved the issue.

[Clint Bach]

I had a noise with my g0766. It all went away after I removed the knock out bar from the spindle. Boy did I feel, well... Sometimes it's the stupidly simple things that bite me the hardest...

YMMV....

Clint

[Brice Rogers]

I had vibration on my G0766 and it was a knocking sound. It turned out that I didn't have the headstock locked down. Stupid on my part.

[Clint Bach]

Just a thought... Removing the headstock from the bed would be too much of a job for me. That thing is more weight than I can handle by myself. But, you could loosen the head and put some rubber or foam pads between the head and the lathe bed temporarily. If it still knocks you know it's the head. This might tell you where to look for the noise. Have you checked if that washer behind the spindle pulley is tight? I wonder what that washer actually is supposed to do...

Clint

[Harold Rosee]

PART 1.

I also had this exact same problem sine I bout my G0766 new back in May. It started a noticeable vibration around 1050 rpm up to around 1140 rpm where it went away. I have just been turning around that speed and ignoring it. I have never called Grizzly. Just didn't want to mess with it until a few days ago. I searched and found this post and I am glad I did. I had really never done a good job at leveling my machine. So I went out in the garage and got out the level. I got everything level and sure enough all but a little bit of the vibration was gone. But I wanted it perfect so I looked some more. I did notice that the spacer between the pulley and the bearing appeared to be out of round. While running the lathe real slow I noticed that the belt had a bad spot in it that made a slight jerk each revolution even though the pulley was running true.

[Harold Rosee]

Part2.

So I remove the parts including the pulley so I could get at the spacer. What is interesting about the spacer is the hole in it is larger that the shaft by a good 1/8 inch. Did they put the wrong spacer on my lathe? It does have a little raised race on the side that touches the bearing but there is no way to keep it centered. I scratch my head and put it back together. The part is just $7.25 so I ordered another one just to see if it's the same. Has anyone else had there's off?? Are you seeing the same thing?

At the same time I ordered a new belt but NOT from Grizzly. I ordered a Gates 220J6 belt off Amazon. I put it on today and happy to report that all vibration id gone. It is smooth as can be even with my chuck on. So in the end the proper leveling got rid of 97 percent. The belt got rid of the other 3 percent.

The only thing that bugs me is that spacer. While it's not causing me a vibration problem it is all over the place and doesn't look right.

I know this is not the Grizzly forum but it's where the OP posted so I added mine here.

Harold

[Roger Chandler]

Part2.

So I remove the parts including the pulley so I could get at the spacer. What is interesting about the spacer is the hole in it is larger that the shaft by a good 1/8 inch. Did they put the wrong spacer on my lathe? It does have a little raised race on the side that touches the bearing but there is no way to keep it centered. I scratch my head and put it back together. The part is just $7.25 so I ordered another one just to see if it's the same. Has anyone else had there's off?? Are you seeing the same thing?

At the same time I ordered a new belt but NOT from Grizzly. I ordered a Gates 220J6 belt off Amazon. I put it on today and happy to report that all vibration id gone. It is smooth as can be even with my chuck on. So in the end the proper leveling got rid of 97 percent. The belt got rid of the other 3 percent.

The only thing that bugs me is that spacer. While it's not causing me a vibration problem it is all over the place and doesn't look right.

I know this is not the Grizzly forum but it's where the OP posted so I added mine here.

Harold


Harold, I put a note for you on the GGMG. There is a recess in the side of the pulley, and that raised area on the side of the spacer fits into the side of the recess on the pulley...sort of like a mortise and tennon. Check to see if that spacer is seated all the way into the recess and tighten down the pulley with the set screws onto the spindle, as that is what holds everything in place. It could have vibrated lose, and could be a very easy fix.

[Patrick Morris IV]

A friend of mine has the 766 and had the same problem. We corrected his problem, after checking for bed level, by putting a blank on the lathe so that it would be out of balance and spinning it up to the start of vibration (also between 900-1100 rpm) then checking each of the feet for movement. If a foot seemed to be moving even slightly, tightening it towards the floor solved his problem.

Oops, didn't see that this post started in 2018 ;-)