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glue block

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I made a round piece of wood by using a 4" hole saw in the drill press and glued it to a turning blank. The next day I turned a 2" tenon on the end and mounted it to the chuck. The wood cracked however as I was hollowing out the bowl and I was lucky I still had the headstock backed up to my bowl. So my question is what type of wood should I use for this application so it won't crack and have my work piece flying across the shop?

Thanks, Martin
 

john lucas

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What kind of wood did you use? was it dry or wet? You say you turned a tenon on it, did you turn the tenon on the bowl or the glue block? A glue block shouldn't crack by itself. I use poplar or maple for glue blocks.
 
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Hi John,

thanks for your reply, it was pine and it was dry. The tenon was cut on the glue block, the idea was not to loose any wood of the turning blank but that didn't work out this time. So the maple is a better choice but also more expensive and harder to get. Do you use a 1" plank to cut your glue block out of or something thicker? The poplar seems as soft as pine, but you had good experiences with it? I can get that at the local Lowe's. Maybe cutting a recess into the glue block and using the chuck in expansion mode will work better? I had cut a tenon and clamped on to the glue block and that part just broke clear off.
 
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A couple questions

How large was the tenon, and how large (dia and lenght) was the bowl blank?

Did the chuck require a dovetail tenon, and did the tenon match? How long was the tenon? Did you have a catch?

I have used chucks that require a dovetail, and when opened to near max opening, the ends of the jaws will bite into the tenon and start to split the tenon, especially if heavily tightened.
 
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Hi Dale,

I made a 2" tenon which fit tight in the claws of the chuck, but I did have it clamped fairly tight. I don't want it to come loose either. I do know what you mean about the corners of the chuck digging in to the tenon when it is too large. That was not the case. My blank was about 8" across and 5" deep, so not very large and I had my tail stock up against the other end for extra support which worked out real well for me. I noticed the crack in the tenon and removed everything and ended up cutting a recess in the bottom of the bowl and chucked it that way, but now I have to finish the bottom of the bowl which I was trying to avoid.
 

john lucas

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Cutting a recess might work but it sounds like the problem you had was weak piece of wood. A 2" tenon on soft wood can easily split with an 8" blank that is 5" deep. I would go with a bigger tenon and a more solid wood. I have 4" jaws and I use 3 1/2 inch square blocks. I just clamp the jaws down on the corners of the square blocks. I've only lost a few over the years and I turn a lot of stuff.
 
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If I recall correctly, John Lucas has a very helpful tutorial on various methods of reverse chucking to finish the bottom of your bowl. As a newbie myself, I understand it's a problem, but solving problems and growing in skill is a lot of what woodturning is all about. Perhaps John or someone else can point you in the direction of help with this common turning task.

Dean Center
 
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I wouldn't use flat-sawn softwoods, especially softwoods with large distance between annual rings. They split pretty easily. If you have quartered or close to it, no problems. Preferred, at my house, are diffuse-porous hardwoods like bass, maple or cherry.

There is an optimum size for a tenon or a mortise for any set of jaws. It's one where the jaws have the greatest amount of metal in contact with the wood. That said, dovetails are wedges, and want a good shoulder or good bottom in the mortise to wedge against. With that, a lot of size difference over optimum is forgiven. Get a good shoulder, remember that a wedge acts by being a bit larger than the opening it fits into, and don't risk the pinions on your chuck by torquing down. All it does is split. Snug is all you need.
 
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Hi all,

thanks for all of the tips, I am getting a lot of useful information. I have already trashed the broken piece, but the comment on grain direction makes sense. As well as the size and the force on the tenon. I will also try the faceplate method and use a denser wood. Better be safe, I feel like I got lucky.

Martin
 

odie

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I use waste blocks and screw center chucks all the time......works well for me. The rule of thumb, is you cannot glue waste blocks on anything but dry seasoned bowls ready for the second turning. (You need a low moisture content for the glue to adhere properly.) I cut them from clear studs into squares, and then the corners lopped off into 8-sided blocks prior to gluing them to the bowl. The only time this isn't strong enough, is it won't survive a severe catch....and will split. So, this probably isn't great advice for the rank beginner. :rolleyes:

-----odie-----
Here is a small spalted Hackberry bowl, and the photos were convenient for posting here, but I use
these glued waste blocks up to my maximum size for my 16" lathe.......never had a problem with
this method.
IMG_4563.JPG
Same bowl, but after the finish turn:
IMG_4567 (2).JPG
 

hockenbery

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is you cannot glue waste blocks on anything but dry seasoned bowls ready for the second turning.
That is only true if you leave the glue block on for a long time or use a glue that won’t bond to wet wood.

I have used glue blocks for a lot of wet wood natural edge bowls. Turn the mounting area on the lathe with a slight concave matching the concave of the glue block face.
Put 2 beads of thick CA on the wood, spray accelerator on the glue block, center the glue block and on th bowl, turn the glue block as it meets the wood. The little twist widens the glue out into the concave area making a large surface area glue joint. This is readdy to turn imeadiatly. So true the outside and hollow.

Glue block is removed by hitting the glue line with a flat chisel.
The CA fractures. A glue not stronger than wood.
Clean the glue off the block with a light scraping cut and 50-100 bowls can be turned using the same glue block.

I don’ have the glue block on more than 30 minutes.
I have had students leave them atttached and the glue fractures in about 2 hours when the bowl begins to warp.

Just another take on glue block using wet wood
 

odie

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I don’ have the glue block on more than 30 minutes.
I have had students leave them atttached and the glue fractures in about 2 hours when the bowl begins to warp.

Thanks for your response, Al.......

From a limited perspective, I suppose you would be correct. :D

-----odie-----
 

hockenbery

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From a limited perspective, I suppose you would be correc

Kelly,
your perspective is more than limited.
Lyle Jamieson showed me this the CA glue block on wet wood.
He learned it from Rudy Osolnik

You do need to get to a symposium some day to see the enormity of what is going on in woodturning.
Hope to see you at a National some day. How far is Omaha?
 

odie

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Kelly,
your perspective is more than limited.
Lyle Jamieson showed me this the CA glue block on wet wood.
He learned it from Rudy Osolnik

You do need to get to a symposium some day to see the enormity of what is going on in woodturning.
Hope to see you at a National some day. How far is Omaha?

To the contrary, Al........

There is more than one way to look at the input here, and I am not interested in the general projection of "the herd". I am happy with the directions my turning is taking me, whether others agree with my methods, or not.

-----odie-----
 

Bill Boehme

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Odie, I don't know why you exhumed a thread that was more than seven years old since the last post. The OP hasn't posted anything since October 2011 and hasn't logged in since April 2013.

FYI, there's more ways than your way to do things. Don't make the mistake of thinking that your way is the right way. Al and many others including me have had great success using CA glue on wet wood. It is something that I learned when I first started turning fifteen years ago. But, as Al said, if the wood is very wet you can't lollygag around because wet wood is going to eventually move.

I deleted your last post because your comments violated forum rules for civil behavior.

Since this is a very old thread I am closing it for any further comments.
 
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