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Noise Issue on my Jet lathe

Jerry Bochenek

Jerry Bochenek

Joined
Sep 30, 2018
Messages
79
Likes
252
Location
The Villages, Florida
I have a Jet 1640EVS lathe that is 13 months old. As long as I have owned that makes what I would describe as a muffled growling noise at around 110 rpm speed. The noise only occurs when the speed is at around 110 rpm. It will growl until I slightly increase or decrease the speed off of the 110 rpm speed. Also, I can hear a light growl when I am turning the lathe down to zero and the speed passes thru the 110 rpm on its way to zero. I have disconnected the belts and checked the tightness of all set screws on the pulleys. As an experiment, with the lathe running at about 600 rpm I pulled the plug and let coast to a stop and the machine did not make any growling sound. That leads me to believe that it is not a bearing issue. I'm also wondering if the noise might be associated with the inverter or the motor braking system. Other then this noise, the lathe works fine. It's more of an annoyance because it does not seem to effect the performance of the lathe although I am concerned that it may be a problem that could continue to get worse over time. I spoke to Jet support and let them listen to a recording of the sound and they want me to take the head stock in to one their authorized repair centers. I called the repair facility a they said it might take about 4 weeks before they could llok at my headstock.

Before I do this I was wondering if anyone has any experience with a similar noise and have any ideas on what may be causing this and if this is something I should be concerned with at this point.
 
I actually had this very same issue with the Jet mini I bought in 2001. Got the same response. Took the lathe in and they replaced the bearings and I have used it ever since. It sits idle most days now, but I still run it up to do a pen or a bottle stopper or small box now and again. I'd still like to find one of those square clamp blocks for it, but don't remember who makes them. Searched this forum over and over with no luck.

Don't let a little annoyance become a major issue. Have it looked at now if you can afford to be down those four weeks.
 
Use the four weeks to clean and organize the shop (all shops need organizing at one point or another), sharpen tools, buy more things that either you need or think you will need. Regarding the wait- my father said that anticipation is greater than realization.
Thanks for sharing the story.
 
When there is a noise at a single rpm, and at no other, there is a high likelihood that it is a harmonics issue. A bearing issue is either a rumble or squeal, but doesn't occur at only one speed. Most bearing noise will get dramatically worse with high rpm. My advice, live with it. Just how often do you find yourself turning at 110rpm? Shut if off when it is at 111 rpm and you won't have an issue! LOL
 
Richard Coers said:
When there is a noise at a single rpm, and at no other, there is a high likelihood that it is a harmonics issue. A bearing issue is either a rumble or squeal, but doesn't occur at only one speed. Most bearing noise will get dramatically worse with high rpm. My advice, live with it. Just how often do you find yourself turning at 110rpm? Shut if off when it is at 111 rpm and you won't have an issue! LOL
Click to expand...
I was going to mention, when do you turn at 110? Just go faster or slower, problem solved. I also think is harmonics, not a bearing issue.
 
At very low drive frequencies the PWM output from the inverter to the motor won't have the same effect as a sinusoidal current. So as Richard indicated, the rough driving waveform could be exciting some mechanical resonance. You might possibly be able to reduce the vibration by increasing the PWM carrier frequency if that option is available. It's difficult to guess if there is any real mechanical problem. I assume that you don't have excessive belt tension. The poly-V belts should only have enough tension that you would be able to flex the belt about a half inch at mid span. I once had a buzzing noise that I traced to to a belt cover door.
 
Dan Bevilacqua said:
Does this occur at 110 rpm when the belt is on the high speed pulley as well as on the low speed pulley?
Click to expand...
Dan, it occurs when the belt is on the high speed as well as the low speed. Although the rpm's are a little different as they are measured by the spindle drive pulley. Also, I completely removed the belt and it still makes the noise at th low rpm.
 
Jerry Bochenek said:
Dan, it occurs when the belt is on the high speed as well as the low speed. Although the rpm's are a little different as they are measured by the spindle drive pulley. Also, I completely removed the belt and it still makes the noise at th low rpm.
Click to expand...

Since you removed the belt and the noise is still there, you have obviously ruled out the spindle bearings.

I have another question with regard to your reference to the different rpm's when on the high vs the low pulley. I assume you are testing this with a bare spindle (no load at all). Is the noise present when the speed dial is at a certain location (e.g. 10 o'clock) regardless of rpm and of which pulley you are using?
 
Dan Bevilacqua said:
Since you removed the belt and the noise is still there, you have obviously ruled out the spindle bearings.

I have another question with regard to your reference to the different rpm's when on the high vs the low pulley. I assume you are testing this with a bare spindle (no load at all). Is the noise present when the speed dial is at a certain location (e.g. 10 o'clock) regardless of rpm and of which pulley you are using?
Click to expand...
Dan, Yes the noise is present when the speed dial is set at a certain location regardless of which pulley I am using.
 
Bill Boehme said:
At very low drive frequencies the PWM output from the inverter to the motor won't have the same effect as a sinusoidal current. So as Richard indicated, the rough driving waveform could be exciting some mechanical resonance. You might possibly be able to reduce the vibration by increasing the PWM carrier frequency if that option is available. It's difficult to guess if there is any real mechanical problem. I assume that you don't have excessive belt tension. The poly-V belts should only have enough tension that you would be able to flex the belt about a half inch at mid span. I once had a buzzing noise that I traced to to a belt cover door.
Click to expand...
Bill, I don't know how the rest of you is doing, but your vocabulary is all back to normal! Which suggests your brain cells are getting enough oxygen, anyway.
 
Alex Garcia said:
I actually had this very same issue with the Jet mini I bought in 2001. Got the same response. Took the lathe in and they replaced the bearings and I have used it ever since. It sits idle most days now, but I still run it up to do a pen or a bottle stopper or small box now and again. I'd still like to find one of those square clamp blocks for it, but don't remember who makes them. Searched this forum over and over with no luck.

Don't let a little annoyance become a major issue. Have it looked at now if you can afford to be down those four weeks.
Click to expand...


This guy wl make you a clamping block among many other items. Bob
https://www.facebook.com/pg/rickthetoolguy/posts/
 
I had a similar experience with a few month old Powermatic 3520B. It would occur during 14-17 Hz output of the inverter, low or high pulley ratio. I could start it by putting a slight pressure or drag on the handwheel if there was nothing on the spindle. Once it started the growling the vibration would continue until the speed would be changed from that output frequency. It made no difference if the headstock was clamped to the bed or unclamped or the position along the bed. Replaced spindle bearings, no change. Replaced inverter, slight improvement initially. Made an effort to stay out of that frequency range. A few months later I was power sanding a large bowl and thought I was in the low speed range but was in the high range and operated in the problem frequency range for half an hour. The outboard motor bearing started making noise. Replaced the bearing. Happened again a few months later and this time the bearing was loose in the aluminum end housing. Replaced the motor and problem reappeared a few months later, though not as noticeable. Replaced the drive belt as the original belt had a set in it. No change. Rockler had received a demo lathe about the same time I received mine. Tried the Rockler unit and it would exhibit the same characteristic, less noticeable. Was going to change some of the inverter parameters but decided it is more fun to just turn. Problem is still there, I quit worrying about it.
 
Bill Boehme said:
At very low drive frequencies the PWM output from the inverter to the motor won't have the same effect as a sinusoidal current. So as Richard indicated, the rough driving waveform could be exciting some mechanical resonance. You might possibly be able to reduce the vibration by increasing the PWM carrier frequency if that option is available. It's difficult to guess if there is any real mechanical problem. I assume that you don't have excessive belt tension. The poly-V belts should only have enough tension that you would be able to flex the belt about a half inch at mid span. I once had a buzzing noise that I traced to to a belt cover door.
Click to expand...
Bill - I've been wondering if the VFD might be causing the chattering sound from the motor running at low speed. I notice that if I am running the lathe at around 700 to 800 rpm's on the large pulley that after 30 minutes the VFD cooling fan turns on and continues to run for about 30 minutes after I turn the lath off. I'm not sure if this is normal for the VFD to warm up enough in 30 minutes of lathe time to cause the VFD cooling fan to turn. I really have no knowledge of VFD's and how they should operate under normal circumstances. The more I am researching the more I'm starting to wonder if the VFD is the culprit causing the chattering sound from the motor.
 
Jerry Bochenek said:
Dan, Yes the noise is present when the speed dial is set at a certain location regardless of which pulley I am using.
Click to expand...

Jerry, I am thinking that it may be the inverter/motor, as you have stated. I have a somewhat similar situation with my 1640; however, mine is not a noise. Mine is a slight vibration (maybe a rapid pulsing) at a certain frequency around mid to high 800's rpm on the high pulley, and around 350 on the low pulley which so happens to be the same setting for both rpm's on the speed control, and it also does it without the belt attached at that same setting.

It is nothing more than an annoyance to me. I don't need to turn at that limited speed range, and the vibration can easily be removed by a little movement of the speed control. Most people would likely not even notice it. I just tend to unrealistically desire perfection in an imperfect world. I have also checked out some other lathes, and they seem to do the same type of thing (different speed), some worse, some at more speed control ranges and some less. The owners of the lathes I checked out did not even realize the vibration until I pointed it out. They said they never noticed it. Again, it is me having to over analyze things.

It also happens at a couple other positions of the speed control but to an insignificant degree. At higher speeds and speeds avoiding these limited parameters, there is no vibration. By the way, I think this lathe is fantastic, and a great quality piece of machinery.

I contacted Jet, and they think it is harmonics of the motor at certain speed ranges based on the frequency of the vfd. Maybe this is what is going on with yours as far as the noise is concerned.

Hopefully, some electronics experts on this forum will provide some insight.
 
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Jerry, my previous post was being drafted while you posted yours. In any event, the fan in the vfd will turn on when the motor has been running at a low speed. The faster the motor turns, the greater the cooling fan produces cool air passing by the vfd to cool it. I looked at an online manual for a Delta "e" series vfd, and it explains that the vfd can be set so the fan runs at all times or comes on when a certain temp is reached, and other settings. I would not try to mess with the settings.

Mine does the same thing; but, it has never come on when running at higher speed or on the low speed pulley.
 
yes...harmonic.....just move sprees up or down....

I once owned a civic h_onda.....on trip out west develop noise from front left wheel area.....no shaking.....would move around at what speed it would sound off at.....3-4 mph speed change it would stop.....annoying when it was @ speed limit.....anyway got home and had it checked out with honda mechanic driving me riding.....he agreed....harmonic......Honda has since announced quality problem with some metal purity......in older models
 
Dan Bevilacqua said:
Jerry, I am thinking that it may be the inverter/motor, as you have stated. I have a somewhat similar situation with my 1640; however, mine is not a noise. Mine is a slight vibration (maybe a rapid pulsing) at a certain frequency around mid to high 800's rpm on the high pulley, and around 350 on the low pulley which so happens to be the same setting for both rpm's on the speed control, and it also does it without the belt attached at that same setting.

It is nothing more than an annoyance to me. I don't need to turn at that limited speed range, and the vibration can easily be removed by a little movement of the speed control. Most people would likely not even notice it. I just tend to unrealistically desire perfection in an imperfect world. I have also checked out some other lathes, and they seem to do the same type of thing (different speed), some worse, some at more speed control ranges and some less. The owners of the lathes I checked out did not even realize the vibration until I pointed it out. They said they never noticed it. Again, it is me having to over analyze things.

It also happens at a couple other positions of the speed control but to an insignificant degree. At higher speeds and speeds avoiding these limited parameters, there is no vibration. By the way, I think this lathe is fantastic, and a great quality piece of machinery.

I contacted Jet, and they think it is harmonics of the motor at certain speed ranges based on the frequency of the vfd. Maybe this is what is going on with yours as far as the noise is concerned.

Hopefully, some electronics experts on this forum will provide some insight.
Click to expand...
Thanks Dan, I also really like my 1640 and think it is an excellent lathe. I also agree that the chattering noise in the narrow speed range is more of any annoyance than an operational problem. The purpose of my posting this in the first place was to see if anyone else experienced the same issue and if there are any potential problems in the long term if I did not pursue this. Plus, I still have about 4 years left on the Jet 5 year warranty should this problem morph into a major problem in the future.
 
Jerry Bochenek said:
Bill - I've been wondering if the VFD might be causing the chattering sound from the motor running at low speed. I notice that if I am running the lathe at around 700 to 800 rpm's on the large pulley that after 30 minutes the VFD cooling fan turns on and continues to run for about 30 minutes after I turn the lath off. I'm not sure if this is normal for the VFD to warm up enough in 30 minutes of lathe time to cause the VFD cooling fan to turn. I really have no knowledge of VFD's and how they should operate under normal circumstances. The more I am researching the more I'm starting to wonder if the VFD is the culprit causing the chattering sound from the motor.
Click to expand...

Mechanical resonances can often be solved by adding mass or bolting the legs to the floor. I found that on my Jet mini lathe that I was able to fix an annoying vibration at certain speeds by adjusting the preload on the spindle bearings. This was done by screwing the handwheel a little tighter. It's possible that at very low frequencies the inverter could be the exciting source that causes something on the lathe to sing (or howl), but I wouldn't hold out much hope that replacing the inverter will fix the situation. Sometimes running the lathe slow with the belt in the high speed range and under a heavy load there could be strange behavior, but that is most likely to be the speed surging and not an audible vibration.

Probably the most common operating mode for the fan inside the inverter is to be temperature controlled. When I turn my lathe off the inverter fan continues running for roughly a half minute. In hot weather the fan continues to run for several minutes after the lathe is stopped.
 
Thanks everyone for your input. Based on all the responses, I think I will just live with the Chattering for now. The machine works great in all respects and the chatter is only an annoyance at this time. Should it evolve into something more serious down the road I will take it in to a Jet repair facility.
 
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