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Thread: Hollowing Questions ???

  1. #1
    Join Date
    Jul 2008
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    Hollowing Questions ???

    I have been running into a problem when i hollow vessels with my hollowing rig and thought i would put some information out here to see if anyone can help or has any ideas. I get alot of catches/grabbing when hollowing and have been trying to figure out why its happening.

    ****I hollow around 600-800 rpm and sometimes higher
    ****sharpen the tool before and druing the hollowing
    ****clear out chips every couple cuts with air gun
    ****cutter is set center off the tool rest
    ****tips are cut to approx 50' angle using a platform on my grinder and the tip is rounded like a scrapper
    ****tried to use only pulling cuts from center out - and working in sections - the most catchy/grabby area is the side at the widest part - happens with every vessel
    I have posted pictures below of the normal type way i set up prior to hollowing for reference - and i usually have the tool rest and the rig set closer when i start




    I recently ordered a goose neck tool for my Monster hollowing rig and they were a great help in suggestions to correctlng things but i want to see what other people are doing or if they had the same problem - even after the suggestions today im still having the same problem...wondering if i need to sharpen the tool differently
    Attached Thumbnails Attached Thumbnails P1010029.jpg   P1010029_renamed_15725.jpg   P1010030.jpg   P1010031.jpg   P1010033.jpg  

    P1010034.jpg   P1010036.jpg  
    Last edited by Dan Mosley; 01-02-2010 at 03:32 AM.
    First you have to learn the rules - Beginner
    Then you have to learn advanced rules - Professional
    Then you disregard the rules - This takes you to the master level................

  2. #2
    Join Date
    Oct 2006
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    You say the cutter is at center at the tool rest. How is it looking 6" or so away from the tool rest (where the cutter is inside the bowl)? If the boring bar is not level, what may be at centerline close to the rest could be a bit off as you get away from the rest. Try adjusting the tool rest up or down (or leveling the boring bar by adjusting the height of the articulating arm) and see if it makes a difference. Also (and you probably already know this), light cuts are key. Lastly, as I've gotten more comfortable with things, I've increased the lathe speed and seem to get fewer catches. Once things are round, I'm often running in the 800 to 1200 rpm range for hollowing. Still, getting the feel for the light touch was the biggest help for me.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  3. #3
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    Vaughn - good idea ill try moving it up some in the morning as you suggested and see how that works out - I can increase the tool rest up a bit as well as the rig and test it out....thanks.....and yep im trying to make the light cuts but the catches keep comming.....your idea may be the key...thanks
    First you have to learn the rules - Beginner
    Then you have to learn advanced rules - Professional
    Then you disregard the rules - This takes you to the master level................

  4. #4
    Join Date
    Jun 2009
    Location
    Southern NH
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    6
    Dan: I don't use a Monster rig, I do my hollowing freehand and am no stranger to grabbing and catches. The area giving you trouble is, I think, the most difficult to work with. I sometimes raise the boring bar slightly above center and rotate the cutter counterclockwise a little so it's in a trailing position. Makes it a little more friendly. I have also noticed that if I don't keep smoothing as I go early on, when I get to the difficult area on the far left I get more grabbing. Light pull cuts in this area, if it's smooth to start with have been helpful for me.

  5. #5
    Join Date
    Dec 2007
    Location
    Tellico Plains, Tennessee
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    4,353
    Dan,
    I don't use a Monster rig either, I use the Don Pencil hollowing system, which is essentially free hand as well... with the elbow rest on the handle, I think I have better control on the cutter and don't seem to get that many catches... I've also bought a Termite tool that seems to work if the vessel isn't too narrow at the mouth... I'm think about trying the termite cutter in the Don Pencil system ... I just have to get a scraper, that I've stripped out the screw head, off the system before I can try it.
    Chuck
    Tellico Plains, TN
    https://www.etsy.com/shop/TellicoTurnings
    My parents taught me to respect my elders, but it's getting harder and harder to find any.
    If you go looking for trouble, it will usually find you.

  6. #6
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    Oceanside, So. Calif. 5 mi. to the ocean
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    Vibration

    OK I am a newbie to woodturning. When I was a kid I spent much of my time in the shop. My dad used a wood lathe, however, most of the time it was the metal lathe.

    He worked to keep all tools, arms, levers, etc. as short as possible because it takes darn little to set up virtually un-noticeable vibration that will cause nasty things to happen. The cutting part of the tool may be fairly near the tool rest. However, it looks to me that the other part if way too far away. It is also not a straight line (another vibration maker).

    It looks like there is a good, short, solid set-up from the tool rest to the cutting tip. However, I think the tool rest is just acting as a fulcrum to transmit vibration from the other side to the cutting tip.

    I also notice that the bowl is attached further away from the headstock than I would expect...again introducing a slight instability.

    Now that you have read all of this stuff from someone who has never done it, you can go have a nice cup of coffee and laugh like the dickens.

    Enjoy,

    Jim
    First of all you have to be smarter than the machine.
    VOTING MEMBER

  7. #7
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    No laughing, Jim. You bring up several good points.

    With the hollowing rig like Dan has, I've gotten in the habit of resting my right forearm on the articulating arm to dampen the vibrations. The fulcrum/lever issue is inherent in making a hollow form. Part of the challenge is finding the "sweet spot" for a particular cut to keep the vibrations minimized.

    You're also right about having the vessel attached as close to the headstock as possible, but in the first picture, I believe the cone-shaped thing you see is part of a jam chuck, and not actually part of the vessel. (I don't think this is where Dan's seeing the vibration.

    Dan, in looking at the pics again, it looks like you've got the base of the articulating arm lined up nice and straight with the bed ways. I've found that often I can reduce the vibration by moving the base to different positions, usually with the vertical support part swiveled around towards the back side of the lathe. You might try experimenting around a bit with that position to see if that helps. Also, different degrees of "folding" of the arm seem to affect the vibration. Here again, experiment around and see what works best for you.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  8. #8
    Dan, I have the same exact setup as you (from lathe to hollowing rig) and have experienced the same problem as you--guess I would not call my problem as a catch but as significant vibration. Seems to be worse when I'm pushing the cutter rather than when I'm pulling. Like you, I've tried different speeds, cutter angles, cutter heights, etc. with little difference. Hope someone has a solution.

    Charlie

  9. #9
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    Jun 2009
    Location
    Southern NH
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    Dan: The swan neck tool will help reduce the torque. I find it helps to do all the hollowing I can with the straight tool. If I can get relatively far out toward the outside wall, I don't have to remove as much material with the angled cutter. I made some swan neck tools, one with a Hunter cutter, one with a round disc cutter. Both are finishing tools and thus remove material more slowly. Helpful. And as Charles says, pull cuts work better. Another thing to try is orient the blanks so the grain is parallel with the lathe bed. This will result in short chips being removed rather than long curls, and NO end grain to cut. You may not get the shapes you want but it's easier and good practice.

  10. #10
    Join Date
    Jul 2008
    Location
    Palm Springs, Ca
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    Thanks to all - I got the goose neck today and I am going to try it out on the next day I have off.........I agree on the pull cuts - repositioning the rig around to see if it makes a difference -

    I use my indexing tool and hog out as much as i can prior to setting up the rig and i agree it makes the hollowing go easier.

    I also use my Ci1 to square off the bottom and then the cutters on the rig to round the bottom curve which seems to work well and quick - the cuts on the bottom are light because i am a long way off the rest at times but it makes finishing off the bottom easy.

    I think its a matter of practice and time.........which i dont have as much as i would like..........LOL

    Ill let you know about the gooseneck when i can........thanks
    First you have to learn the rules - Beginner
    Then you have to learn advanced rules - Professional
    Then you disregard the rules - This takes you to the master level................

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