Flex shaft vibration

[Dale]

On my last carve I heard a change in pitch of my machine and noticed a vibration in the flex shaft. The vibration is only on the Z truck end (I have a Carve Tight spindle) and goes from the Z truck up about 8 inches and then disappears. The flex drive has never been overheated. I inspected the core and spring and found nothing wrong. Both ends of the shaft are square and I did the twist test with less than 1/4 turn. I turned the spring and core around (end that was in spindle now is in the cut motor) with no help. I suspected the spindle bearings might be bad so ordered a new Z truck. I installed that and still have the vibration. After more research here found that rotating the top hat may help so tried that. The vibration was reduced a little but not much and after running for about one minute using the cut motor test found the spindle getting hot, the flex drive was not even warm yet. The first inch of the core was hot but I think that was just heat transfer from the spindle. Now I don't know if the new spindle is bad or could the shaft vibration cause the spindle to run hot. Guess trying a new flex shaft will be next unless someone has another idea.

[DianMayfield]

Dale, I am not sure what the cause might be. But, I am down in Burley (near Twin Falls) and can send you my spare used flex shaft assembly to test that angle before you buy one. I was having jittery carve problems and bought a new one to see if it cleared up the problem (it didn't). There were no issues with the shaft/sheath.

If you would like to try it, let me know and I will throw some lube on it tonight and get it in the mail in the morning. PM me your address.

[unitedcases]

We're you carving or cutting? My flexshafts are always smooth but when I cut they get jittery. A dull bit will transmit some vibration as well. And what kind of lube are you using?

[bergerud]

Check the core for end play. It should float freely in the sheath. The vibration could be because the core is being compressed between the spindle and the motor. When pushed back into the motor, the spindle end should only stick out about 1/2". (At least that is as far as it sticks out on both of my machines.) If the circular part of the flex sticks out, it may be getting compressed. You may have to clean out the motor end.

[Dale]

The vibration started while I was carving, but after I changed the Z truck I was using the "check cut motor" feature so there was no bit installed at all. I have about 10 hours on a new cut motor and I used the lube from LHR for the first time when I changed the motor. The core is free floating and when pushed fully in there is 1/2" showing. I did not mention it in my original post but it seems I have to push quit a bit harder to get the shaft to seat into the spindle .

[bergerud]

I did not mention it in my original post but it seems I have to push quit a bit harder to get the shaft to seat into the spindle .

That may not be free floating if the core jams into the spindle. Try pushing the core by itself all the way into the spindle first and then the sheath into the top hat.

[Dale]

Dan, That did it! Vibration is gone and spindle does not run hot.

Thanks for everyone's help.

Dale

[Rob Mulgrew]

Having this same exact problem, But I Just put in a brand new cut motor and new flex shaft. It has a loud vibration and the spindle is heating up fast. Tried 100 times to reseat it with no improvement. Tried lubricating the flex shaft with no improvement. While it does slide all the way in both sides, it is not smooth and it's hard to get the flex shaft back out of the motor. A couple times I had to take the motor right out. Any other ideas?

[bergerud]

How far does the spindle end of the core stick out when pushed all the way back into the motor?

I think you will have to find out why the core is tight in the motor. If both parts are new, something may be defective.

[Rob Mulgrew]

It sticks out 5/8 which is what how my old one was also but the old flex shaft always came right out and fit much looser. I have my old motor still, maybe change out the end pieces where the flex shaft inserts and see if there is a difference?

[bergerud]

I do not think you can change the end piece on the motor shaft. You need, I think, to find out why the core is tight in the motor end. Is the core frayed? Twisted? Is there some problem with the square hole in the motor? If the core is ok, maybe you may need work on the square hole in the motor.

[Rob Mulgrew]

Thanks for your replies bergerud. I decided to call LHR and go through their process of elimination being the parts are brand new. Israel suggested I remove the spring silencer around the core and see if that takes away the vibration. Its 95 degrees in the shop now so I'm going to run it later when it cools down see what happens. I'll post what the fix for this was when we get it figured out.
If that doesn't work, I think I may put my old cut motor back in just for one run and see if it the problem is the motor, flex shaft or spindle.

[bergerud]

My guess is that there is something wrong at the motor end. If the core is tight in the motor it might be held off center and be wobbling.

[Rob Mulgrew]

Dale I got your PM but your inbox is full and I was not able to reply back but anyways, I just realized that I had a bad spindle bearing. The bottom bearing was hard to turn and had a spot where it would catch and then release when turning it by hand. I bought and installed the new 6002v bottom bearing and 6000du top today. After these bearings break in we'll see if things run smoother. I should also mention that the flex shaft now goes in and out smoothly with the new motor, maybe cause I've taken it out and put it back in 100 times. We'll see how it goes over the next few runs. I'll update this as necessary. Thanks for all the responses!

[bergerud]

That type of problem has been rare. How many hours on the machine?

[Rob Mulgrew]

Your right that its a rare problem. I talked to Israel at LHR and he never heard of someone changing those out but it could be the environment my machine runs in. I have about 800hrs on this and have never had dust collection or air conditioning and its been super hot here. Not ideal but I have to work with what I have at the time. Were out of breakers and will in time have to put in a new electrical box to run a dust collector etc.
For the bearings we have an industrial supplier locally who stocks these bearings (yes sealed and rated for high RPMs) and it was much cheaper to try replacing them myself before buying a new carvetight spindle.

[bergerud]

Thanks for the info. Make sure the tolerance ring is ok. The bearing might have been slowly spinning in it. Some Loctite behind it might be a good idea. The tolerance ring vibrating out has been a common problem. (I have my own type of spindle and have some experience with these parts.)

[Rob Mulgrew]

Thanks for the info. Make sure the tolerance ring is ok. The bearing might have been slowly spinning in it. Some Loctite behind it might be a good idea. The tolerance ring vibrating out has been a common problem. (I have my own type of spindle and have some experience with these parts.)
Can you elaborate what the tolerance ring is? Getting into the spindle is brand new for me. Also while the there is not much vibration or rattling like before, the spindle with the new bearings is too hot to touch after about 5 minutes of running. Is this the new bearings breaking in? The heat is not in the flex shaft just the spindle itself.

[bergerud]

The tolerance rings are corrugated metal rings that fit around the bearings. They make the bearings a snug fit. Google tolerance ring.

Did you not see them?

The bearings do run hot for a little while. Just do short easy projects.

[Rob Mulgrew]

Okay I know exactly what your talking about just didn't know the proper name. I took those out and wiped them down. They did have some lube on them which I assume came from the flex shaft over time and probably could of had the bearings spinning in there. Hopefully I don't have to take this apart for a long time but if I do I'll be sure to get a little locktite behind them. Great tip. Thanks for your help.