noise on my Jet Mini lathe

[ebrannon]

My Jet Mini lathe varible speed is making a noise.

I have had the lathe a number of years, but do not use it that much. I brought it to Florida with me this winter and have been using it frequently for the past month. When home, I typically only use it for buffing as I have a larger lathe I work on.

The noise is a low squealing type noise, and I cannot tell if it is the belt, or a motor bearing. Sounds like a belt rubbing the side of the wheel, but why would it start doing that?

Anyone had problems with motor bearings going out on Jet mini's?

Any ideas on what this could be? It is not the drive bearings, but could be in the motor or the belt.

I plan to keep using it until something "happens" and then I will know if it is the belt or something more serious.

I always assumed the Jet mini is pretty bulletproof.

e

 

[Jake Debski]

Start with the easy stuff first. Remove belt from motor pully and run the motor. No noise, check the pulley set screws to see if they are loose, a common problem. If loose check to see if pulley shifted and is hitting on housing or rubbing on belt edges. Need to do this on both pulleys.

Bearings should be last place to look.

 

[MichaelMouse]

Should be able to eliminate the squeal by aligning the pulleys. On my 3000, the company wants me to set the pulleys one ridge off the rise to the next size rather than all ridges in line. Allows me to use the belt without touching L or R with the bump of the joint and the squeal and stink of fraying.

 

[ebrannon]

may be the motor

I checked the belts, and they seem fine.

The motor is getting very HOT and the breaker kicked out on it. A bit nervous that the motor may be going.

Possibly the outlet I am using has low voltage, or I am working the lathe too hard. Does not seem that way, but it is overheating.

Checked with Jet, and they want $245 for a new motor plus shipping. I only paid $350 or so for the lathe 5 years ago. Anyone know a source for rebuilt motors for this lathe?

 

[DOCworks]

Might want to check the brushes on that motor as if it's been setting up and now you are using it they can cause problems.

 

[Rick M]

At 5 years, it sounds like yours must be out of warranty.

On the variable speed motors, you've got a couple of brushes you might want to inspect for wear. I'm not certain what kind of noise you'd be hearing if a brush was worn down to the brass base, but it would certainly cause electrical havoc on the commutator and loss of power.

The motor is not particularly difficult to unmount if necessary to access both brush holders, or even pull the end bells off for further inspection. That will also allow you to assess the condition of the motor bearings.

Anything not too severe can probably be fixed fairly easily DIY, and if not inclined or significantly damaged, look locally for a motor repair shop that might be cheaper than a complete replacement.

I rebuilt one for a Jet midi that failed because the power lead to the brush holder rubbed the commutator until it shorted (mfg defect). I can help further if you need more info or pics.

 

[Bill Boehme]

Here are a couple troubleshooting tips:

• Does it make the noise all the time or just when you are turning something? Is the noise different for a light finishing cut on a spindle as opposed to a heavy cut on a large turning? If the noise is dependent on the amount of load, it is very likely to be a worn out belt. You can't necessarily tell by looking at the belt whether it is worn out. Old belts get hard and do not grip well. A five year old belt is very likely to have hardened and also developed ozone cracking. Also, if the belt has worn to the point that the ribs make contact with the bottom of the grooves in the pulley then the belt will slip. Poly-V belts are no different than regular V belts in this regard -- they run on the sidewalls of the V where there is wedging action to provide traction -- not on the peaks of the ribs. Try this just for fun: turn the belt inside out and then pinch it together to make a sharp bend. Do you see any tiny transverse hairline cracks?
• Do you hear any high pitch growling or rough vibrating sound when making a moderate or heavy cut, but not at other times? This could mean that the set screws on one of the cone pulleys has loosened up enough to allow a bit of vibration. Sometimes this sound can make you think that you toolrest is loose.
• Both the AC and DC motors on this lathe run hot under moderate or heavy load so that is not a reliable indicator of a problem. It would not hurt to take a peek at the brushes on DC motors at least once a year. Worn out brushes usually do not make much noise, but they will cause the lathe to lose power and, if neglected too long, damage the commutator.
• With the belt disengaged, do you hear any "funny" noise from the motor. Try this with the motor running and then turn the motor by hand with the power off. Turn the spindle by hand to see if there is any ticking, rumbling, or any other sounds. Feel for any radial or axial free play in the spindle. If you find any of these problems, then you very likely have bad bearings. Don't put off replacing bad bearings -- if a bearing seizes, it would score the spindle that it is mounted on. Bearings are cheap, but a new spindle or motor armature isn't. Replacing the bearings on the spindle is easy. Replacing the bearings on the motor takes a bit more in the way of tools and skill, but still is not a daunting task.

 

[ebrannon]

I will give these a try Thursday and see what I find and get back to you.

Your advice is much welcome.

Ed

 

[ebrannon]

UPdate

Well, this is the status:

1. It is not the belt, or brushes. Checked both (replaced belt and inspected brushes).
2. I removed the belt and the noise stopped, so I believe the noise is coming from the headstock bearings.
3. the noise comes and goes. Sometimes it does not make any sound, then it will suddenly kick in, and it varies with the speed of the lathe.
4. I have not checked voltage, but will as soon as I can find a volt meter to check the line voltage.

Bottom line, I think it is the headstock bearings. I have replaced one in the past, so it is not a big deal, but given that these would be the 3rd set of bearings, they most not be that robust or sturdy.

The problem may have resulted from overtaxing the capacity of the lathe. I had some unbalanced pieces with quite a bit of rumbling and rocking before I could round it out.

If anyone is still following this thread, and has some experience with Jet Mini lathes, pleases share ideas. All the comments have been very helpful to me.

e

 

[DOCworks]

Ed,
Are you going to be at the Fl Woodturning Symposium? You indicated you were in Florida. Bring it with you, there are a bunch of guys who I'm sure would be happy to take a look at it. Just a thought. It's this weekend 4, 5 and 6 at Lake Yale.
Bill

 

[MichaelMouse]

Well, this is the status:

Bottom line, I think it is the headstock bearings. I have replaced one in the past, so it is not a big deal, but given that these would be the 3rd set of bearings, they most not be that robust or sturdy.

The problem may have resulted from overtaxing the capacity of the lathe. I had some unbalanced pieces with quite a bit of rumbling and rocking before I could round it out.

Stethoscope, or the mechanic's substitute, the screwdriver, should confirm where you have bearing problems as reliably as the heat that might come if you continue to use them. They come in various grades, so you might want to move up one or two if those you're replacing are of lower quality.

 

[Bill Boehme]

Well, this is the status:

1. It is not the belt, or brushes. Checked both (replaced belt and inspected brushes).
2. I removed the belt and the noise stopped, so I believe the noise is coming from the headstock bearings.
3. the noise comes and goes. Sometimes it does not make any sound, then it will suddenly kick in, and it varies with the speed of the lathe.
4. I have not checked voltage, but will as soon as I can find a volt meter to check the line voltage.

Bottom line, I think it is the headstock bearings. I have replaced one in the past, so it is not a big deal, but given that these would be the 3rd set of bearings, they most not be that robust or sturdy.

The problem may have resulted from overtaxing the capacity of the lathe. I had some unbalanced pieces with quite a bit of rumbling and rocking before I could round it out.

If anyone is still following this thread, and has some experience with Jet Mini lathes, pleases share ideas. All the comments have been very helpful to me.

e

I agree that the bearings are the most likely suspect based on the symptoms. Rather than the standard bearings that Jet specifies, I would go with higher grade bearings as MM suggests. If you can get angle bearings in the same form factor then that would be even better. Regular bearings are designed only for radial loads, but lathe work usually involves axial loads and that is why I suggest the angle bearings. Get bearings that are rubber sealed on both sides. I would stay away from metal shielded because of wood dust. Definitely do not use open bearings.

I would not waste time measuring the line voltage. It won't tell you anything that you do not already know and low voltage won't cause any of the problems that you are having.

I think that I am approaching the time to replace the bearings on my Jet mini also. There is a rumbling vibration when a heavy load is applied. First I plan to check the screws where the lathe is bolted down just to make sure that they are tight.

 

[Wayne Spence]

Jet mini lathe

Bill Boehme- I too think my jet mini lathe is due for new bearings. I am not familiar with angle bearings but will look into it. Do you have any experience with ceramic bearings? Cost may prohibit them .

 

[Bill Boehme]

Bill Boehme- I too think my jet mini lathe is due for new bearings. I am not familiar with angle bearings but will look into it. Do you have any experience with ceramic bearings? Cost may prohibit them .

No, I am not familiar with ceramic bearings, but I suspect that they may be for specialized applications like perhaps very high speed or high temperature. Ceramics, in general, are brittle so that might need to be weighed against their advantages.

You could go to the Timken/Fafnir or NTN web site to download engineering manuals on their bearings. The manuals will give specifications on the various grades and types of bearings.

 

[ebrannon]

Opps, did not get your message before I left. Did attend Friday and Satuday, but not for Sat night or Sunday. Had a good time and learned a lot. Still working on the problem.

Does not seem to overheat now, so it may have been from "pushing the capacity" but I think the bearings are what is making the noise.

 

[ebrannon]

sources for better bearings

I orded from Jet, but would like a source for better bearings in the future.

 

[fred holsclaw]

the bearings in all jet lathes need to be replaced with in a year as they are not sealed
get a set of sealed bearings and the should last you a few years longer then shielded ones
had a 1014 jet new bearings in less then a year
1442 jet new bearings in less then a year
friend has a jet 1642 needed new bearings in less than a year
all the above units had bearings replaced with sealed bearings and they will last a lot longer then what jet uses

 

[Bill Boehme]

the bearings in all jet lathes need to be replaced with in a year as they are not sealed
get a set of sealed bearings and the should last you a few years longer then shielded ones
had a 1014 jet new bearings in less then a year
1442 jet new bearings in less then a year
friend has a jet 1642 needed new bearings in less than a year
all the above units had bearings replaced with sealed bearings and they will last a lot longer then what jet uses

Interesting. My Jet lathe is nearly 5 years old and still on the first set of bearings and first belt although the belt is starting to look its age. My lathe doesn't always get heavy use, but it does get used quite often. I have gotten the motor blistering hot on a few occasions from turning things that were near the capacity of the lathe. I try to keep better tabs on the motor temperature these days although the motor will withstand rather hot temperatures -- for a while -- before it fries.

 

[ebrannon]

close out

As a final note...

It was the bearings. Changed both with new Jet bearings and noise is gone.

I think I will try to find better bearings when they need to be replaced again. This is my second set in 3 years. Maybe I worked it a little too hard. Having worked on my Stubby for the past 6 months, I may have pushed this one too hard. Do not know, but issue solved.

Thanks for all your sage advice and help.

Ed

 

[Bill Boehme]

.... the bearings in all jet lathes need to be replaced with in a year as they are not sealed ........

I had my Jet mini apart yesterday and the bearings are rubber sealed. Something that can be mistaken for bearing noise would be noticed if the preload is not set properly. It should be just enough to insure that the inner race is not slipping on the spindle, but not so much that there is noticeable drag.

 

[opfoto]

Here is a link that may help with the selection of the bearings....

http://www.ntnamerica.com/website/d...n_a1000xi_ball_and_roller_bearings_lowres.pdf

Can be confusing but if I can sort it out I will share the information I get. I have a supplier that is maybe 10 minutes (depending on traffic) from me!!!
I will visit them this week and try to find out a bearing to replace both the 6004 and 6005 bearings with some as Bill suggested (rubber ended and angular). I will report part number as well as cost.

 

[Bill Boehme]

Perhaps you could use 7000 series 15° angle ball bearings that are rated to ABEC-3 or ABEC-7. I believe that either the labyrinth rubber seals (no contact) or the full contact rubber seals would be the way to go. Given the dirty environment, I would not settle for anything less even if I had to stick with plain old simple single row deep groove ball bearings with rubber seals.

 

[ebrannon]

Great. Would like a source.

 

[DOCworks]

Does anyone have the specs. on these bearings or do you just take the number off the side of the bearing? Sorry for the dumb question.

 

[Bill Boehme]

Does anyone have the specs. on these bearings or do you just take the number off the side of the bearing? Sorry for the dumb question.

The number on the side is sufficient. The basic numbers for the Jet Mini bearings are 6004 on the handwheel end and 6005 on the drive end. The 60 series bearings are single row deep groove radial contact ball bearings. If, instead, you wanted to use angle contact ball bearings, then you would use the 70 series bearings.

There will usually be some other letters and numbers to indicate things like shielding or sealing, lubricant, cage type, clearance, and certification. Different manufacturers use different nomenclature for these things so you almost need the manufacturers catalog to decipher things.

Most makers use the letter Z for metal shields so a 6004Z is open on one side and metal shielded on the other. Things are a little muddier for sealed bearings, for example, some aftermarket Chinese manufacturers might use 6004-2RS or 6004RRS for rubber sealing on both sides without specifying whether it is a full contact or non-contact labyrinth rubber seal. Manufacturers like NTN will specify the difference. For example, an NTN 6004 bearing with full contact rubber seals on both sides is labeled as 6004LLU while non-contact rubber seals on both sides would be labeled as 6004LLB.

 

[Bill Boehme]

Also, I might be mistaken about this, but I think that the bearings in my Jet Mini use phenolic ball cages rather than the more common stamped steel cages. I did not write down the suffix letters before reassembling everything, but I do remember that they are Chinese made and seem to be reasonably good considering that they are around five years old and still going strong.

If you get the angle bearings, make certain that you orient them correctly so that the static preload on them is in the direction to press the inner and outer race together and not in the direction that pushes them apart. Normally, very little external preload is necessary becase they often are designed with some amount of built-in preload.