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Why did this catch (photos)

Discussion in 'Getting Started' started by Robb Nielsen, Jun 8, 2018.

  1. Robb Nielsen

    Robb Nielsen

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    I’m posting some pictures here to help show how I’m getting catches and run backs. On this one, tool rest just above center. Trying the ABC method to get cutting. I was trying to cut foot to rim but couldn’t get it to work for me. In this example I was cutting lip to foot. And my way down the foot I get this catch. If I’m taking off dust which is mostly what I’m doing it seems ok but when I raise my handle to get my tool more level and start getting shavings I get the catch.

    41D6C571-CFE8-4F01-A01B-916DD29ED989.jpeg

    C19A6DDA-488D-42C6-A662-E2B10677515C.jpeg


    And then this attempt was trying to begin the cut at the foot of the bowl but I get run back as you can see in these pics. Tool rest at center height.

    FE2B300A-1288-49D0-8D41-6FF7B41636D3.jpeg

    D540198D-117F-48AC-A60A-6277A4EEAB3E.jpeg
     
  2. Mark Wollschlager

    Mark Wollschlager

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    Try cutting from the foot to the rim.
    Outside of bowl, foot to rim.
    Inside of bowl rim to foot ( bottom of bowl )
    You can turn 'against the grain', but is might be considered a more advance technique if you want good results.
     
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  3. hockenbery

    hockenbery AAW Advisor Staff Member

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    Robb,
    I will answer your message. The top two photos look like you are trying a pull cut.
    I think this is a more difficult cut to master than the push cut.
    If the nose of the tool contacts the wood you get a catch because the wood can drive down onto the edge.
    When the cut is made below the nose then the wing is slicing and there is not a possibility of a catch.

    In the bottom two photos. This is a hard cut going straight into the end grain. I avoid this cut when I can. A lot of people cut this way with the flute closed but it Is hard going into the endgrain.
    Roll the gouge so that’s the flute is at 3 o’clock. 30714E53-C60D-4A71-85B2-920E1E7D1845.jpeg


    I prefer to cut this face with a series of cut across the grain. Fast forward to 10:45 in the video below to see the series of bevel riding push cuts to cut the surface.

    This is how I turn a bowl. The bevel riding push cut is the cut I recommend to new turners.


    View: http://www.youtube.com/watch?v=Lo0bGSafZq4
     
    Last edited: Jun 8, 2018
    Mark Wollschlager likes this.
  4. Fadi Zeidan

    Fadi Zeidan

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    You mentioned tool rest above center. Tool rest needs to be just below center where if you lay the gouge flat on the tool rest, the bottom of the flute will be at center.

    You are probably opening the flute too much and engaging more of the side than you should. That also could explain the run back.

    http://turnawoodbowl.com/no-catches-using-a-bowl-gouge-with-confidence/
     
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  5. Ely Walton

    Ely Walton

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    It appears the nose of the gouge is ground much lower than the wings... I have better results when the line of the wings to the nose is ground straight, not drooping when viewed from the side... YMMV and reasonable people may have other opinions but this is my experience.

    Ely
     
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  6. Robb Nielsen

    Robb Nielsen

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    Maybe that’s why as I’m trying to do the inside he bevel seems to burnishing the sides, not cutting the sides. I feel like I’ve got the tool closed quite a bit and I’m afraid to open it up and have the point dig in. This is how I’m getting the burnishing and not cutting effect. Tool rest positioned so that gouge, when parallel to the floor is right at or just a touch above center. But I can’t get it to bite in and cut. Got it a few times and actually got long curly shavings for the first time but can’t find that sweet spot again. Guess I’m really afraid of a bad catch. You guys have been a huge help though.

    7507E214-E34D-443D-A055-F578873AAE29.jpeg 506AA1A2-FEA1-4ACC-B7F8-1E61C51819C1.jpeg
     

    Attached Files:

  7. Robb Nielsen

    Robb Nielsen

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    Here is the grind. I think I see what you mean about the nose being below the wings. Let me see if I can figure out how to fix that ...

    Here’s what it looks like now. (By the way, does everyone prefer in line pictures or attached thumbnails. I’m on my phone so inline pics look good. But I don’t know if they’re coming out giant on a computer monitor)

    8E29FAC2-E0C2-4A3E-A046-3154081D333F.jpeg
     
  8. Zach LaPerriere

    Zach LaPerriere

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    Very good photos Robb, and a great openness to learning.

    In addition to what's been said, if you grind a secondary and possibly tertiary (third) clearance bevel, your chance of catches will go WAY down. Keep your primary bevel no greater than 1/16" and you won't get bit by the same catches. It's still important to understand where and why catches happen, but a small primary bevel reduces the likely 80% or more in most cases

    With the Oneway jig the easiest way to grind a secondary bevel is to just bring the V arm in roughly 3/4" after sharpening.
     
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  9. Robb Nielsen

    Robb Nielsen

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    1265DB42-6304-4763-BC82-FC4089DD10EB.jpeg

    The advice here is great guys, thanks again.

    So here is my attempt at a longer fingernail grind. Flipped it over and free hand ground/hogged away at it until I had shape I think you guys are describing. Then back to the jig for the 45-50 angle.

    Zach, interesting idea. I may try that as well after trying this grind for a moment. Here goes nothing.

    At this point I think have more metal shavings on the floor then wood shavings. ;)
     
  10. Bill Boehme

    Bill Boehme Administrator Staff Member

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    The rough surface leads me to think that the tool was cutting without bevel support. If the tool was angled upwards without the bevel supporting the cut then the conditions are favorable for getting a dig-in. The grind on the bowl gouge might also be a problem. It is hard to tell for certain because of the angle of the pictures, but there appears to be a very high hump in each wing and possibly a dip on each side of the nose. There can make the tool hard to control.

    Re: your latest post. A 45° nose angle might be somewhat grabby for a beginning turner, I would favor a nose angle closer to 60°. Also , with a 45° nose angle there is a greater chance of losing the bevel on the interior of a bowl as the tool approaches the bottom.

    While grinding away some of the heel of a bevel is often useful in preventing heel bruises, the bevel itself in my opinion isn't the cause of catches. I think the crux of the problem is the result of forcing a bowl gouge with an acute nose angle to cut past the point where bevel contact can be maintained ... in other words the tool goes from cutting to scraping. Relieving the heel gains a little additional depth, but it's not an absolute cure.
     
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  11. Robb Nielsen

    Robb Nielsen

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    43DEEB47-AEFB-484E-B7C0-904E0D13D93B.jpeg

    That new grind you guys recommended made a huge difference in my ability to pick up a cut and keep it going. Wall thickness is decent in terms of consistency but I had a hard time making a smooth transition to the bottom. Also when I turned my tenon (which is did with a parting tool) and remounted it to hollow it out it wasn’t running very true. So you can see how the rim is thinner and thicker as it goes around.

    You can also see my tooling marks which I kept trying to get rid of but couldn’t make a clean cut. As I pushed the tool through my hand and into the bowl I couldn’t do it really smoothly so transitioned those into the rings down the walls. Bring on the 80 grit

    I don’t have a way to chuck back up and finish the bottom but for now, I’m happy with experience today. Thank you all for your help!
     
  12. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Basically, the sides are too steep for the size of the bowl and there is not enough room to transition. Try starting with the sidewall at the rim having an angle about 45° and gradually curve the inside so that it is like a slice off the side of a basketball. Think of it as continually transitioning from the time that you start at the rim until you reach the center of the bottom. Don't worry about depth. It is a natural tendency to wan't to use as much of a piece of wood as possible, especially if you paid money for it. However, a nice continuous curve from rim to bottom is much easier and also looks better than straight sides and flat bottom.
     
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  13. Robb Nielsen

    Robb Nielsen

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    Well, went through the grits with a power sander from 80 to 240 and some steel wool. Sanding sealer and polish than backed off the shine with steel since I think the wood is pretty enough without a distracting gloss.

    So, first bowl ever thanks to all if you guys on here. Now to go show the wife what she gets for a few thousand bucks in tools lol.

    And I’ll figure out how to do the bottom later. I’ve seen some adjustable face plates to hold bowls I’ll look into unless you guys have a favorite I should look at.

    CC1EB1F9-0885-4521-AFE8-38D91C3C83CE.jpeg 7BFB29B3-8DD6-4A29-B8B5-84E35C2ED46A.jpeg
     
  14. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Congratulations, very nice first bowl. Far nicer than my first bowl.

    There are all sorts of ways to reverse the bowl to clean up the foot. The least expensive would be a jam chuck. There are also Jumbo jaws / Cole jaws / Bowl jaws (depending on the brand the name varies). If you have a lot of extra money that is burning a hole in your pocket then you could get a vacuum chuck.
     
  15. Robb Nielsen

    Robb Nielsen

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    Good advice. After working on the outside and trying for that “just one more finishing cut...repeat...” I made it a lot smaller than it started out! So I was trying to maximize the volume I could get out of it.
     
  16. hockenbery

    hockenbery AAW Advisor Staff Member

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    Nice job on the bowl. Changing the grind likely did the trick.
    Also you may be pushing too hard on the bevel.

    One thing that I struggled with as a self taught turner was holding the tool too tight.
    If you have played any game with a stick like baseball, lacrosse....you should have been taught to cradle the stick not strangle it. Holding the tool too tight can become a destructive cycle.

    Get a catch because the tight grip made the tool go the wrong way
    Grip it tighter from fear
    Get another catch......

    In turning and life we seldom make good decisions based on fear.
    Much better to base decisions on science, facts and history.
    You are building a set of historical results.
     
    Last edited: Jun 9, 2018
  17. Mike Johnson

    Mike Johnson

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    On a smaller diameter bowl like this one you could sand the bottom flat if the wood is stable and dry. Larger bowls tend to change there shape slightly after turning and a flat bottom becomes slightly curved and the bowl will not sit flat on a table. One trick you can use on smaller bowls is to turn a recess in the bottom of the bowl instead of a tenon and mounting the recess on the chuck to turn the inside of the bowl. This method eliminates having to remove the tenon which can be a hassle if you don't have the jam chucks, donut chucks, etc. to reverse mount the bowl by the rim. You basically turn, sand, and finish the bottom recess, add any beauty rings or embellishments and then mount the recess onto the adjustable chuck holding it by putting pressure against the inside recess in an outward direction. The recess needs to be a minimum depth and proper shape of the recess for the chuck jaws to hold the piece for turning. Depending on the wood species and strength of the wood this will determine how much wood is needed on the bottom to support these outward forces. A tenon mount can be tightened with an extreme amount of force from the chuck jaws, a recess mount can limit the outward forces exerted on the bottom of the bowl depending on the strength and thickness and depth of the wood around the recess.
     
  18. hockenbery

    hockenbery AAW Advisor Staff Member

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    Taking off the bottom I usually jamb chuck the bowl.
    This is a little intimidating if you haven’t done it in a class.

    1. Measure the thickness of the bottom
    2 don’t cut deeper than that Thickness.

    A straka chuck aka doughnut chuck works well. You need MDF( or more expensive plywood) 4 bolts, and fun foam. Give secure access to the bottom. How to make one is for holding a ball, hence the padded depression on the bottom plate. For bowls you can pad where the rim rests.
    http://aaw.hockenbery.net/Making a straka Chuck.pdf


    This is how I reverse chuck a bowl - fast forward to 34:10

    View: http://www.youtube.com/watch?v=sCZWsHB4vlM
     
    Last edited: Jun 9, 2018
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  19. robo hippy

    robo hippy

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    Looking at the first picture, your gouge nose is kind of snaggle toothed. Also, it looks like you are doing more of a peeling cut, which is how you approach spindles with a roughing gouge. Come off the bevel when doing that type of a cut on a bowl does lead to catches. I have a bunch of bowl turning videos up on You Tube which may help. Having a hands on session would be a lot better. I don't know if you are planning on coming down to the Symposium in Portland next weekend or not, but great learning experience. Demonstrations are a bit on the expensive side, but you can go through the vendor area and instant gallery for only the cost of parking... If you can make it, swing by my booth in the vendor area and I can spend a little time with you...

    robo hippy
     
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  20. Gerald Lawrence

    Gerald Lawrence

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  21. John Torchick

    John Torchick

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    Nice bowl! That is the great thing about this forum- people who want to learn or expand their skills have a number of experienced turners that share their skills! I need to go back and re-read this thread. Thanks to all for your contributions!
     
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  22. Robb Nielsen

    Robb Nielsen

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    Well I figured I’d cap off this thread with the successful turning of the bottom. Found the face chuck at my local woodcraft today.

    Cut the foot at a slight concave so it will sit flat as you gentleman suggested. Bought the thin parting tool also to do the job. As you guys also suggested I left the tail stock in place until the very end. And then burnt my sig into the bottom with a hot iron my wife made for me a few Xmas’s back for something else. You know, for the future archeologists who uncover this someday

    Thanks again guys. This was fun and I’m anxious to do more.

    1432ACA7-44D9-4AC5-9F96-2F9D62F2E4A7.jpeg 17BBF834-868A-4958-A133-1E47A101E80E.jpeg
     
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  23. hockenbery

    hockenbery AAW Advisor Staff Member

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    Congratulations!
    It is the first of many.
    Each one will be better than the last any your are starting out with a good one.
     
  24. Mike Johnson

    Mike Johnson

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    Good job!

    When turning the tenon on your bowls it helps to run the tail stock up to the tenon and apply the live center point to make an indentation into the center of the tenon this makes it easier to align the bowl onto the cole jaw chuck and get it mounted in the center by using the tail stock to keep it centered against the cole face plate while you are tightening the cole jaws.
     
  25. Robb Nielsen

    Robb Nielsen

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    I figured the cole jaws were self-centering. But it wasn’t quite centered when turning the foot. I’ll try using the tail stock detent next time before tighting the cole jaws.
     
  26. Bill Boehme

    Bill Boehme Administrator Staff Member

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    The problem is that the rim will almost never be perfectly round plus the plastic or rubber bumpers are slightly flexible. As you said, having a centering point will help, but it won't be absolutely perfect especially for larger bowls. Another thing that helps sometimes is to rotate the bowl slightly to find an orientation that is closer to being centered.

    I had a senior moment a couple days ago and removed the waste block too soon so now I am fiddling with getting a piece centered on my Vicmarc bowl jaws (same thing as the Nova Cole jaws only bigger).
     
  27. Emiliano Achaval

    Emiliano Achaval Administrator Staff Member

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    I prefer adding a block to the V pocket, that way you dont have to move it. I have several blocks that fit in the pocket, for different angles, with a little magnet, so I can put them on top of the grinder when not in use.
     
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