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Thread: Glue Block Failure

  1. #1

    Glue Block Failure

    Hello-
    Just getting started turning. I turned one small bowl by gluing a block to the bottom of the bowl with a piece of paper bag between the block and the bow. Glue on both pieces. This worked fine on my first bow. Next time I had rounded the outside and was starting to hollow out the bowl when the glue up failed and the 'not a bowl yet' rolled onto the floor. The glue held the paper on each piece so I guess I could say the paper failed? I suspect not enough glue to soak the paper or perhaps either the bowl blank or the black were not perfectly flat.

    All stand by and wait for an actual informed opinion!

    Thanks in advance
    ScottIMG_4807.jpg

  2. #2
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    Skip the paper all together, make sure both sides are flat and true and glue them together.

  3. #3
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    Like Chance said. I never use paper for a glue block. Also it is best to have end grain as the glue block.
    When working I had more money than time. In retirement I have more time than money. Love the time, miss the money.

  4. #4
    Scott, do you have a scroll chuck? If so, I think you'll have an easier time gluing the waste block to what will be the bottom of the bowl, turning it into a tenon then turning it off when you're done.

    If you don't have a scroll chuck (put it on your list), you might want to modify how you're getting the waste block off the finished bowl. Rather than the paper bag business (the risks of which you've already learned), glue the waste block directly, wood to wood (making sure it's flat, good contact, all that). To finish the bottom of the bowl, take a chunk of wood (like a piece of 2x8 for the size bowl you're showing), mount it to a face plate, and turn the surface into a shallow cone (making sure you know where your screws are). When you've finished with the interior of the bowl, take it off the faceplate, put your cone on the lathe spindle, and reverse compression chuck your bowl with the open side against your "cone" (using the cone to center it) and squeezing it there with the tailstock live center against the waste block. That will allow you to turn away the the waste block down to a small nub. It will also allow you to make the bottom of your bowl a little concave, which will help it sit flat on a flat surface. Turn the nub down as far as you're comfortable, then saw or chisel off what remains and sand smooth.

    If you don't have two faceplates, you might have to re-true the cone each time you remount it to the faceplate.

    If this doesn't make sense, say so and we can find pictures or a Youtube to show you what I'm talking about.

    Enjoy!

    Dave
    Last edited by Dave Mount; 05-18-2020 at 2:30 PM. Reason: Spelling

  5. #5
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    Another way to fasten a flat bottom of a blank to a faceplate is to use double-sided tape. The good stuff, called woodturner's tape at Woodcraft I think, not double-sided carpet tape.

    A friend of mine uses this method to make large bowls from big blanks. Always holds.

    He applies one layer to the face plate and "burnishes" it tight to the metal before removing the backing. The he applies a second layer to the flattened bottom of the blank. He sticks them together so the layers are perpendicular and applies pressure overnight with a weight or with the tailstock.

    It's sometimes challenging to get the two pieces apart. I use the tape sometimes to hold metal for machining - I force a thin wedge into between the two pieces and wait - it will slowly separate. Repeat until apart. Can clean up with acetone.

    But a waste block glued to the blank and held in a chuck is easier. When done turning part off the waste block, reverse the bowl into a jam chuck and support with the tailstock while cleaning up and shaping the bottom. Clean up the very center by hand.

    However, I usually use an even easier method with a chuck. Instead of holding with a tenon, whether on a waste block or the blank, I first hold the blank by the top (by one of several ways), cut a recess in the bottom and shape the foot completely then turn the outside of the bowl or platter. Then reverse the piece and hold with the recess in the bottom and shape the inside of the bowl/upper side of the platter.

    penta_plates_comp_small.jpg

    JKJ

  6. #6
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    Another method I've used is make a wooden faceplate with a bealle tap. Get some hardwood and tap a hole in it the same size as your spindle. Mount your wooden faceplate on the lathe and turn it round and face it off so it's flat. Then glue it to the bowl blank. You can then turn your bowl and get close to the bottom without worrying about hitting screws or metal chucks. When done, just part off the wooden faceplate and save it for the next time.

  7. #7
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    The whole point of the paper is to make pieces easy to split apart later, so the good news is that it worked! Depending on the paper though you need to be real gentle. I wouldn't use that trick to attach a bowl, but it is great if you're making split turnings, eg for pillars on the front of a clock case or something-- as long as you don't use a pointy live center that will split the halves.

    For a bowl I'd glue the block directly to the blank and then part it off when you finish the bottom.

  8. #8
    Quote Originally Posted by William C Rogers View Post
    Like Chance said. I never use paper for a glue block. Also it is best to have end grain as the glue block.

    William - that surprises me as end grain is not known as a great glue surface. Can you explain the reasoning of using end grain?
    Scott

  9. #9
    Thanks all - After the second failure today (paper glue joint) I think I'm in the market for the 'scroll' chuck. Not sure what the term 'scroll' refers too. Is that Nova chuck I see in a lot of applications appropriate? Does it screw onto my spindle or does it always need an adapter?

    Scott

  10. #10
    Dave - I think I"ve seen some thing like this but...
    1. There's a face plate attached to the glue block. That comes off to finish the bottom. Can it then be used for the cone then don't need 2 face plates?
    2. The term 'cone' leaves a lot to be imagined. pointy? Round? match the curvature of the bowl?
    Scott

  11. #11
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    Quote Originally Posted by Scott Welty View Post
    Thanks all - After the second failure today (paper glue joint) I think I'm in the market for the 'scroll' chuck. Not sure what the term 'scroll' refers too. Is that Nova chuck I see in a lot of applications appropriate? Does it screw onto my spindle or does it always need an adapter?

    Scott
    You can buy a "direct thread" chuck that will fit directly onto your headstock or you can buy an "insert type" chuck that will require a separately purchased adaptor. Make sure you get the right size (i.e. a lot of mini lathes are 1"x8 tip and a lot of larger lathes are 1 1/4" x 8tpi). The benefit of the insert type chuck is that if you ever change lathes you can still use the chuck and would only have to buy the $20 adapter rather than a whole new chuck. The benefit of a direct thread chuck is that you don't have to spend extra money for the adapter and some have reported occasional problems with run out if thread damage, etc. occurs.

    You can watch some youtube videos on scroll chucks (I think Capt. Eddie Castelin has one where he talks about the basics of chucks).

    I started turning bowls with glue blocks and that was fine, but now I own several Nova chucks and would never go back. They are so convenient.

    Good luck,
    Tom

  12. #12
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    Work holding

    Quote Originally Posted by Scott Welty View Post
    Dave - I think I"ve seen some thing like this but...
    1. There's a face plate attached to the glue block. That comes off to finish the bottom. Can it then be used for the cone then don't need 2 face plates?
    2. The term 'cone' leaves a lot to be imagined. pointy? Round? match the curvature of the bowl?
    Scott
    I think by "cone" he means shaping the outside of the block to fit nicely into the curvature at the top of the bowl. This is often called a "Jam" chuck. The thicker the block and the better the shape matches the inside of the bowl the better. This can be tricky to make, especially with a thick jam chuck, but there are tricks. Use caution as too much pressure can cause the sides of the bowl to split, especially if the walls are thin and especially if made with particular woods. An internal cone also doesn't work well on a bowl with a "closed" rim, one that flares inward instead of outward. I also use this method very often with things like goblets and lidded boxes.

    Instead of a cone, I sometimes turn a groove in a flat piece of plywood fastened to a faceplate or held in a chuck. I size the groove so the lip of the bowl fits snugly into the groove. The groove doesn't have to be deep. The unfinished bottom of the bowl is held by pressure with the tailstock and turned as noted. I use a carving chisel or skew to clean off the bottom of the nub. I often hold the bowl in place on the jam chuck or grooved plywood with a number of strips of tape so after I remove the tailstock I can simply turn the nub away and decorate the bottom as desired. If doing this, use gentle cuts, primarily with force in the down the lathe axis towards the headstock to avoid excessive side forces.

    I usually mount a wooden extension into my Nova live center so if I cut into it when approaching the center of the bottom there is no damage to the tool, or make a wooden extension of some sort for the Oneway style live center.

    live_center_MT2_IMG_7914.jpg live_center_threaded_IMG_7917.jpg

    Another way to finish turning the bottom of a bowl or platter is to hold it with a vacuum chuck which you may want to look into some day. You still support with the tailstock as long as possible then the vacuum holds the piece nicely when the tailstock is removed.

    I can recommend a book from our good friend Doc Green with almost everything you need to know about mounting and holding things for turning: https://www.amazon.com/Doc-Green/dp/1565235193 Even the title says so: "Fixtures and Chucks for Woodturning: Everything You Need to Know to Secure Wood on Your Lathe (Fox Chapel Publishing) Advice, How-Tos, and Wood-Gripping Projects for Both Beginners & Advanced Turners "

    JKJ
    Last edited by John K Jordan; 05-19-2020 at 2:51 PM. Reason: clarity

  13. #13
    John kind of covered it. You just need something that will support the bowl and center it. Some do it by cutting a groove in a flat backer board. Another way is to use a thicker blot (like a piece of 4x4 and turn what looks like the end of a baseball bat. Put a piece of padding between it and the bottom of your bowl when you compression chuck it.

    If you only have the one faceplate, you can absolutely change the faceplate from the bowl over to the support board. The only thing is that the support board might not run true after remounting, and you might have to true it up again after remounting.

    Dave

  14. #14
    Scott, here are some ideas about ways to compression or jam chuck your bowl. Lots of ways to do it. Not advocating any one in particular. I tend to use those that fit down inside the bowl rather than those where you turn a groove into a block. The former are generic and can be used over and over. However, you have to keep the tailstock on them, so you'll have to do a little finish sanding after you remove the nub. I don't see that as an issue.

    https://www.youtube.com/watch?v=P00yxA0aHhs

    https://www.youtube.com/watch?v=4YaV4Rrz1gA

    https://www.youtube.com/watch?v=ASc5azQdxKk


    https://www.youtube.com/watch?v=7lyPjwI1GKQ

    https://www.youtube.com/watch?v=AzMDwM1uwik

  15. #15
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    Quote Originally Posted by Scott Welty View Post
    William - that surprises me as end grain is not known as a great glue surface. Can you explain the reasoning of using end grain?
    Scott
    I too thought the glue block was supposed to be side grain????

    Also, I bought a big thread tap so I can screw the glue block (and other special drive pieces) on my headstock.

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