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Thread: Problem ID'ed How do I fix it?

  1. #1
    Join Date
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    Problem ID'ed How do I fix it?

    OK, I have had this problem on bowls and now it is showing up in my spindle work. Side note: I started turning years ago and NEVER had this problem. Now I get a good lathe and good tools, start back and nothing but problems! End of Rant. I find I use a wood mallet all the time. I have a couple and decided to make another. I turned the head from a pecan square, the handle was hickory.


    Look at the head and you can see rings around the head. These rings are low spots that you can feel when you run your hands across it. They don't run all the way around the part. It's almost like an ellipse instead of a round cut.

    There are no knots (hard spots) that the tool would be bouncing on. Of course they don't show till you start to sand the part and these spots being low don't get sanded.

    OK, now what the heck is causing this?????
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  2. #2
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    You are an experienced turner and the problem is new. Have you changed your turning style or work methods? This is a puzzlement. If you were a beginner, I would suggest you should use a large skew to smooth your spindle work. But, I won't do that since you are experienced.

  3. #3
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    This has stumped me Frank. I have had a similar problem when turning around a something like a knot. The thinking being the tool hits the knot, bounced up slight and then digs in slightly. But this one makes no sense to me.

    If it was all the way around the part I could understand. But it is just in this one area. It appears the tool is 'digging in' for some reason. But no idea why. I have increased my turning speeds and I thought this had helped.... but obviously not.

    I did notice the tool rest was not smooth so I ground it last night. I don't think that is it. This is why I gave up turning a few months ago. I was so disgusted.

    Jeff
    Still disgusted
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  4. #4
    Jeff...........I've got a couple things in mind.....First I would never insult you or your capabilities.....so as I ask questions or make suggestions please don't misunderstand my intentions......I don't think the rough spot in the tool rest would do it UNLESS the ring goes all the way around the mallet head.

    IF the rings go part of the way around the mallet head, I'd think 1 of 2 things I'd check.....is the centering of the spindle changing......is the wood moving on the live centers..so it's changing it's centers?....worn bearings....or not enough pressure to hold the spindle on the same center? Or 2....could you be changing the pressure on the handle of the tool or changing the angle of presentation ...but even that would in my opinion put the groove all the way around the spindle unless you are extremely fast ......If it's happening often enough....Try turning on somebody else's lathe with your tools.......But I'd suspect problems with the live centers or bearings in the head stock.......

  5. #5
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    Ken, that makes as much sense as anything since it is a problem I have never had before. This is a old school lathe and I have never done anything to it since I got it. Well other than installing the VFD and replacing a belt a couple of months ago. It was in good shape so I have never torn it down. You may be onto something there.

    Just thought of something, yesterday I noticed a harmonic vibration (I think that is the correct term). Every few seconds on a very steady rhythm it would vibrate slightly for a second and quit, repeating this cycle as long as it was running. Well, it was more noise than a noticeable vibration.I was thinking it might be time for bearings but never thought about it causing my problem.

    Guess I need to blow the dust off the bowl lathe and see what happens when I turn something on it.

    Jeff
    Headed to the Lab to find his dial indicator and check the play and runout

    PS Ken, at this point I have insulted my turning abilities so your not going too. I have been thinking it has to me all along. Now I am not so sure.
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  6. #6
    Jeff.....I install, and maintain Cat scanners, MR scanners and x-ray equipment for a living. Once I got sent up to help a guy t/s a problem....we ended up with a guy from engineering there helping us. We had a Ct scanner that would occasionally creat an artifact on an image. The xray tube on that cat scanner mounts to a 2000 lb frame that rides on a 36" diameter bearing...the patient lays through that bearing and the tube rotates around the patient.......we t/s and t/s........very intermittant......upsets everybody...service...the doctors....the patients.......We finally found the problem.....when the bearing was built (and of course in use it's nearly impossible to see it...just a very small portion of it)...the person building it left 1 ball bearing out of it. The problem only happened when the frame had the mechanical load at a specific place and the empty "slot" was at the top where the missing ball should have been holding the load!

    Good luck!

  7. #7
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    Jeff, I didn't realize when you said, "Now I get a good lathe..." you meant a used lathe. New (usually, and hopefully) means it works well. Yeppers, check for play. Try another turning with scrap wood and see what happens.

  8. #8
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    Watch it Frank! Don't make fun of my Old Arn!

    Ken, I know the feeling of trouble shooting and not being able to find the problem. Done a lot of that in my life time.

    OK guys, gave the lathe a good twice over and nothing yet. Bearings are tight. .0005 is all the movement I can get out of them and that is using a short pry bar. There is .005 total runout in the spindle but that is not going to cause this problem. I checked the spindle, the chuck and the shoulder on the spindle (less than .001 runout on the shoulder) and everything is very consistent and
    nothing wrong I can find. I forgot to put the indicator on the center but it is new and feels tight. I don't think it is the problem.

    I am leaning toward the part was (is) moving when I am turning but I am stumped as to how. One thing I forgot to check was end play. To see if the spindle might be moving in and out, but I don't see how that would cause this problem. The Chuck is a new Oneway, but it could be the problem. I guess I willconcentrate on it next.

    Finished lunch now back to the Lab. But first I need to connect the gas line to my heater. The lab is a bit cold.
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  9. #9
    I know Junque lathes, believe me, I have several (four in my shop now) Were I rich and famous I would own a Oneway or Powermatic but I make do with what I have.

    One of my lathes is old and the spindle runs in bushings rather than a bearings. It too developed what you are discribing, replaced the bushings and the problem went away. Could verywell be worn bearings.

    On the otherhand, one of my other lathes will begin the same harmonics if the belt is too loose. Tightening the belt tension solves that problem.

  10. #10
    I know Junque lathes, believe me, I have several (four in my shop now) Were I rich and famous I would own a Oneway or Powermatic but I make do with what I have.

    One of my lathes is old and the spindle runs in bushings rather than a bearings. It too developed what you are discribing, replaced the bushings and the problem went away. Could verywell be worn bearings.

    On the otherhand, one of my other lathes will begin the same harmonics if the belt is too loose. Tightening the belt tension solves that problem.

    You mentioned changing the belt a couple of months ago. New belts tend to settle down and need readjusting from time to time also may be that it has set for a while and stiffened, you said it has been cold.

    Looking at your piece of wood for the head, the grain obviously is more dense as you turn around the piece, this is why you need to obtain such pieces as Riff cuts or as far from the pith as possible so that the annual rings are straight as possible. This can create some variance in the cut. Pecan is so tough on tools and can be rather mean to deal with. I remember back in the dark ages when teaching was and experience anyone could enjoy, we had a local mill that would give us off cuts and defects of Pecan. Man that stuff was hard on tools.

    Not questioning your experiences and skill level but just thinking outloud


    Ken.... My S-I-L (Machinist) works at a plant that makes MRI ring bearings, I hope it wasn't one of his that created the problem.

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