Mark V vibration while turning bowls

[hugh556]

Hello folks,

I have a mark V that was originally purchased in 1978. I bought it used a few years ago. Whenever I try to turn wood bowls with a chuck, the machine vibrates fairly aggressively. This persists even after I turn the bowl blanks round. The machine does not vibrate when turning between centers, when using accessories (bandsaw and belt sander), or when using other functions like a Jacobs chuck or the sanding disc. The main shaft has a small amount of side-to-side play that can be felt when the machine is off. I checked the two accessory shafts (the upper and lower ones on the left side of the machine), and these two do not have play. I noticed that when I turn the shaft by hand (with the machine off) the belts make a squeaking noise. I am not sure if this could be related to the wobble/vibration problem. I initially believed it was possible that the spindle could have been bent or there was a worn out bearing in the quill. I decided to replace the quill to address these potential issues. I purchased a used quill online since it appeared in good condition. The quill I removed from my machine was a double bearing quill. My research indicates that the double bearing quill was not introduced until the 80's, so it appears as though the previous owner replaced the quill at some point. Perhaps he was trying to fix the issue I am trying to deal with, and it did not work. The quill I purchased was a single bearing quill. I installed this quill in my machine, and it did not make any difference whatsoever. I know that it is possible this quill also has a bent spindle or worn bearings since it is used, but I am thinking it is more likely that something else is the problem since the two different quills gave the exact same performance. I am unsure how to proceed from here, but I am hoping it as a problem that I can fix myself. I am hoping to get some input on what the issue may be. Should I try to return the quill I bought? Please feel free to ask for more information if needed.

Thank you!

[JPG]

What speed are you running? Are the blanks "balanced" after "rounding"?

side to side play? Need new bearing? Easily replaced!

Oh, and how large are the blanks?

[hugh556]

There is vibration at the lowest speed (A), and it gets even more aggressive as the speed is increased. The blanks that cause vibration are about 6-8 inches in diameter. They should be balanced since I take passes until there are no flat spots and the entire circumference is cut. So you’re thinking that the quill bearing(s) in both quills I’ve tried using are bad? Would you recommend replacing the bearing in the single bearing quill or the bearings in the double bearing quill?

Thank you for your response!

[JPG]

For the time being, the single bearing quill will be simpler to replace.

As for balance, round does not always = balanced. Density and moisture content can vary.

[hugh556]

I am pretty sure the blanks were balanced. I have made attempts with several different pieces of wood. Each was a different species, and each was turned round. In every case I am getting the same vibration. I think the problem lies within the machine since there is play in the main shaft. Is there a way of replacing the bearing without a bearing press? Where would you recommend purchasing a new bearing from?

Thanks again!

[roy_okc]

Hugh556,

Does the vibration occur constantly or sporadically?

When I was using my 500 in lathe mode, I had a sporadic vibration when turning bowls and hollow forms. I replaced the single bearing quill with a double, helped some but didn't eliminate the issue. I was using a Penn State Ind spindle adapter to attach to a PSI chuck and think this was one of the other things causing vibration; I put several wraps of teflon plumbers tape around the 1"x8 TPI threaded end, also some sort of compressible washer as I recall, and tightened the chuck onto the adapter as much as I could which helped reduce the vibration more, but again not entirely.

I eventually bought a dedicated midi lathe.

[RFGuy]

Hugh,

I am a novice woodturner having only done it a few years now, but long term experienced woodworker. Not saying I have an answer to your problem, but I have questions that may or may not help. Wanting to know how you are turning the blank. It sounds like every other function on your Mark V is low vibration and only the bowl turning has high vibration. There are different ways you can turn a bowl. Are you using the Shopsmith faceplate attached to the blank, a waste block, worm wood screw, or is it chucked? A vibration like this where the assumed balance is good, etc. makes me think of concentric errors, i.e. the driving axis is offset from the central axis of the bowl blank. Depending on your mounting style on the lathe there could be differing reasons for a significant concentric error to cause a high vibration. One thing to keep in mind is that most lathe chuck manufacturers number the jaws and these MUST be installed in the correct numbered slot or you will have an unbalanced lathe chuck with considerable concentric error. A simple way to test for concentric error no matter the mounting style is to put your tool rest on the end of the bowl blank (parallel to it). Then turn lathe on and use a pencil on one side of the end to make a mark. It will create a circle all the way around the end of the bowl blank and once you stop the lathe you can inspect to see your assumption that the bowl blank is near perfect centered with your mounting is true or not - just inspect to see if you have the same even spacing between pencil mark and outer edge of bowl blank around the circumference. I hope this helps. Good luck.

[hugh556]

Thank you both for your responses.

The vibration occurs constantly whenever I have a bowl mounted without support from the tailstock. I use a Nova G3 chuck with a worm drive screw to turn the outside of bowls and to put a tenon on the bottom. Then I flip the bowl around and mount it with the tenon in the chuck jaws. I double checked and the jaws are installed properly (the numbers line up). I do use an adapter to attach the chuck. The adapter has a cylindrical hole on one end that is slid onto the mark V's shaft (and secured with a setscrew), and a threaded section (male) that the chuck can screw onto on the other side. I guess it could be possible this is the cause of the problem, but it does not account for the play I feel in the main shaft when the adapter is not installed. I do have a faceplate, so I could see if the vibration is still present once a bowl is turned round on it.

RFGuy,
You are exactly correct, the only time I get vibration is when a bowl is mounted without tailstock support. I will have to try that trick with the pencil on a bowl blank. I also know it doesn't have anything to do with me making cuts with my chisels because the vibration occurs without my touching the wood with a tool.

[DLB]

You might try mounting your whole setup (bowl, jaws, chuck, adapter) on the upper aux spindle to check for vibration. It is the same speed as the main, opposite direction of course so make sure everything in your setup can spin in reverse. That should be fine, many lathes are reversible. I agree with you that the felt play in the main spindle is a concern. To confirm, you can feel this with both quills?

You asked earlier about bearings without a press, normally it's possible. You probably need at least a puller, I recommend that bearing separator type if you don't have one. If you drive (hammer) bearings on, it is essential that you only apply force to the race that is being installed. On SS Quills, the inner race is the one with a press fit. The outer race is usually slip fit. My personal preference is Timken sealed bearings but there are numerous quality brands. (Along with even more numerous lesser quality bearings.)

- David

[hugh556]

David,

Mounting on the aux spindle is a great idea! I'm not sure why I didn't think of that. I'll give that a go tonight and see if the vibration continues. To your second point, yes, I can feel side-to-side play in both the original quill and the used one I replaced it with. I will do some research on bearing replacement without a press. It seems to me the most likely problem is worn quill bearings. Once I use the test you suggested I will know for sure whether or not the problem exists within the quill (since that test isolates the quill from the setup). I will post an update tonight with what happens.

Thanks!