# Advice needed, hollowing



## kweinert (Mar 20, 2012)

I know - i probably should have waited until my new tool is ready. But who can resist the siren call of a piece of wood just setting there?

I started turning down the one piece of ash that I rescued from the tree trimmers. It turned down round without and issues (it was between centers) and I got the tenons on the ends for mounting up in the chuck.

I separated the top and bottom of the friction fit lidded box (that's what this will end up being) and chucked up the top. 

By the way: how is it that you folks part off pieces? I haven't advanced quite that far yet - I turn it down to about 1/4" or so and then cut it apart (without the lathe running.)

Well, in trying to hollow out the top I've now loosened it once and actually popped it out of the chuck 3 times.

Both pieces are now in the bag with the shavings.

I have some theories:

1) I'm home sick and probably shouldn't be trying to turn anyhow (no medication aside from aspirin - I may be foolish but I'm not stupid. At least not usually.)

2) Tools not quite sharp enough. I recently bought a sharpening jig and should probably set that up - although for reason 1 i probably shouldn't do that today.

3) This is the most likely - lack of skill. I didn't think it would be too bad - after all, I've done this a couple of times before. Literally, twice before have I turned something like this but both times they were dry turnings and this is pretty wet still.

I'm probably not going to go back and try again today, but I'll be interested in any advice you folks can give me. I probably should call the guy from the turning club that offers mentoring as well.

Thanks.


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## woodtickgreg (Mar 20, 2012)

I use the same technique for parting, works for me. Turning green wood should not be that big of an issue for you. Does your chuck have dovetail jaws to grip the tenon? what kind-brand of chuck is it? Is it tightened very firmly, I really crank down on mine. I am picturing the top as a shallow hollow, Is this correct? If so a round carbide cutter will work for that, look at kevins post on what he did with his first hollow, he went to far but it was impressive what he did with that round carbide tool. I have done shallow hollows like tops with a bowl gouge. If you can post some pics of what you are doing, that will help us to help you. Hope you feel better my friend!


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## arkie (Mar 20, 2012)

Look closely at your tenons. If your chuck jaws are dovetailed, your tenon should be a little more so. If the chuck jaws are not dovetailed on the inside, the tenon should be straight to ever so slightly tapered. the slightly smaller part should be next to the body. 

Next, there should be flat surface on the body around the tenon for the top of the chuck jaws to register against. The wood should only touch the jaws on the inside with the round tenon, and on the ends of the jaws with this flat surface. The end of the tenon should not touch any part of the jaws or chuck.


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## DKMD (Mar 20, 2012)

arkie said:


> Look closely at your tenons. If your chuck jaws are dovetailed, your tenon should be a little more so. If the chuck jaws are not dovetailed on the inside, the tenon should be straight to ever so slightly tapered. the slightly smaller part should be next to the body.
> 
> Next, there should be flat surface on the body around the tenon for the top of the chuck jaws to register against. The wood should only touch the jaws on the inside with the round tenon, and on the ends of the jaws with this flat surface. The end of the tenon should not touch any part of the jaws or chuck.



Agreed! If your pulling stuff out of the chuck, I'd bet 99 out of 100 it's a problem with the tenon. I don't think you can be too anal when it comes to making sure its done right.

I'll bet your also having some issues with tool presentation... Typically a big catch + poor tenon= flying blank! There are lots of ways to hollow a shallow box lid with a lot of different tools. I generally use a small bowl gouge, a spindle gouge, and/or a scraper depending on the wood, the style of the piece, and wind direction.

BTW, if that wood isn't bone dry, a lidded friction fit lid is likely gonna get stuck on or stuck off. If you're interested, Richard Raffan's box making DVD is a good place to start on lidded boxes.

Good luck!


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## kweinert (Mar 20, 2012)

DKMD said:


> arkie said:
> 
> 
> > Look closely at your tenons. If your chuck jaws are dovetailed, your tenon should be a little more so. If the chuck jaws are not dovetailed on the inside, the tenon should be straight to ever so slightly tapered. the slightly smaller part should be next to the body.
> ...



I'll get some pictures up here in a bit.

The tenon doesn't go all the way to the bottom and it does have a slight taper/dovetail in it. When it pulled out at least one of the times it also pulled some small chunks out of the tenon.

Yeah, I know the wood is going to move as it dries out. This is a small piece of ash from some tree trimming and I was going to try the double turn method on it. Basically get it thick wall hollowed and then stick it in a bag with the shavings to gradually dry out for the final turning.

My chuck is a Nova Midi.

Working on processing those pictures, they'll be up in a bit.


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## kweinert (Mar 20, 2012)

OK, so here are the pictures I promised:

Ash Log:
[attachment=3238]

Turned down round:
[attachment=3239]

Ready to split into top/bottom. This is really about as far as I feel comfortable in turning down, preparatory to turning off - although I always just use a backsaw to actually finish off the separation:
[attachment=3240]

Here's what the tenon looks like. You can see the areas where the tenon tore out when it popped out of the chuck:
[attachment=3241]

And here's what it looks like inside the top so far. It looks like there's probably a heart rot that goes all the way through the branch even though it's pretty small here:
[attachment=3242]

The pieces are now back in the bag with the shavings.

Here's a picture of my chuck - bet you've never seen one of these before! 
[attachment=3243]

And thanks to all that have looked and offered comments. I know that none of this is new to most of you. Hopefully I can contribute back at some point in time.


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## DKMD (Mar 20, 2012)

A couple of things come to mind…

That's a very tall box if this is your first go at rough hollowing one. I'd try something in three or four inch range(lid and body together) for a first go… You might be able to part that body into two for something shorter.

The cracks in the endgrain may allow the blank to compress a bit which might loosen the hold in the chuck. You could try to stabilize them with a bit of CA, but I'd probably opt for a crack free blank if you've got one available.

The only thing I can't tell from the photos is whether not the shoulder next to the tenon is flat and perpendicular to the axis of the blank.

What tool are you using to hollow, and which direction are you cutting with it?


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## arkie (Mar 20, 2012)

kweinert said:


> Here's what the tenon looks like. You can see the areas where the tenon tore out when it popped out of the chuck:



I can't be certain from the pictures, but I believe your tenon diameter is too big. Look at the gap between the ends of your jaws when gripping the tenon. Now look at your tenon that has pulled out of the chuck. 

When the tenon is too big, the jaws only contact the tenon at the corners of the jaws and you don't have much gripping surface. That's what the tenon looks like to me - DAMHIKT!

If you have trouble understanding, intentionally turn a tenon that is way too big in a piece of waste. It should barely fit into jaws when they are wide open. You can then see that they only make contact at the jaw corners. If you slowly reduce that tenon, retrying as it gets smaller, you will see how the contact area and grip improve. 

It's a trade-off if you are twice-turning bowls. I generally turn a cross grain bowl with a 2-1/4" tenon to fit my 50mm jaws when it is green. That leaves enough room for me to clean up and bring the tenon back to round, and still grip it in the same jaws after drying.


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## kweinert (Mar 20, 2012)

arkie said:


> I can't be certain from the pictures, but I believe your tenon diameter is too big. Look at the gap between the ends of your jaws when gripping the tenon. Now look at your tenon that has pulled out of the chuck.



One of the drawbacks of being self taught is thinking that what you're doing makes sense :)

I thought that bigger would be better - and it's probably why the other turnings worked - the wood was smaller to start with so the tenon was a better fit from the start.

Thanks - I'll turn the tenon down some more before I chuck it back up.


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## hardtwist (Mar 20, 2012)

I have that same chuck, and have experienced the same things you describe. The two lever system of opening and closing the jaws is very difficult to get good torque on your tenon. I use a large screw driver or pry bar to torque the jaws down and achieve a proper hold on my workpiece. First, tighten hand tight with the levers. this will hold our chuck tight to the shoulder of your workpiece while you crank it tight with a long lever as pictured. The screwdriver in the pic is actually 18 inches long, giving me a lot of torque.
Mike


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## kweinert (Mar 20, 2012)

DKMD said:


> A couple of things come to mind…
> 
> That's a very tall box if this is your first go at rough hollowing one. I'd try something in three or four inch range(lid and body together) for a first go… You might be able to part that body into two for something shorter.



Could be - I just used the piece of ash they cut off and squared up the ends somewhat on the bandsaw, then put it on the lathe.



DKMD said:


> The cracks in the endgrain may allow the blank to compress a bit which might loosen the hold in the chuck. You could try to stabilize them with a bit of CA, but I'd probably opt for a crack free blank if you've got one available.



Might try the CA since the point of my doing this was to work with wood fresh from the tree. Might not get anything but shavings for my efforts but as long as I learn something it won't be a waste of time.



DKMD said:


> The only thing I can't tell from the photos is whether not the shoulder next to the tenon is flat and perpendicular to the axis of the blank.
> 
> What tool are you using to hollow, and which direction are you cutting with it?



It's as flat as I could make it. Created the tenon using a 1/8" Parting Tool. The bottom of the blank does not sit on the chuck face - at least I got that part right :)

I've tried using a 1/4" bowl gouge, my 1/2" skew, and a round nosed scraper. And I've tried both directions - a sure sign that I don't really know what I'm doing, I know. The last time it came off it was the scraper, the other two times it was the bowl gouge. The skew didn't pull it off, but neither was it very effective (mainly due to size.)


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## arkie (Mar 20, 2012)

kweinert said:


> One of the drawbacks of being self taught is thinking that what you're doing makes sense :)



I started out that way myself. Took me years to get mostly over it. Provided you don't hurt yourself doing it, you'll learn far more turning wood than any other way. If you can find a club, or an experienced turner willing to spend a couple hours, you can really shorten the learning curve!


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## kweinert (Mar 20, 2012)

hardtwist said:


> I have that same chuck, and have experienced the same things you describe. The two lever system of opening and closing the jaws is very difficult to get good torque on your tenon. I use a large screw driver or pry bar to torque the jaws down and achieve a proper hold on my workpiece. First, tighten hand tight with the levers. this will hold our chuck tight to the shoulder of your workpiece while you crank it tight with a long lever as pictured. The screwdriver in the pic is actually 18 inches long, giving me a lot of torque.
> Mike



Good idea, thanks.


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## DKMD (Mar 21, 2012)

Here's a YouTube video about holding work on the lathe... Might be something helpful there.

http://www.youtube.com/watch?v=aUXil-5dEeo&context=C4bc1c19ADvjVQa1PpcFOY6EgFpBTHQhPalM_xSaQF1NubJI0NSJ0=


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## Mike Mills (Mar 21, 2012)

I agree with David that it is a very tall box; especially for those jaws.

Even though I can’t tell the tenon size I agree that it should fit as close to possible and still have room to re-true after drying.

I don’t have the Nova mini but I do have a tommy bar type chuck. If you rotate the item you will find a place where two of the holes are close together. On mine, right bar to the top tightens, right bar to bottom loosens. One handed, just like installing a bit in a router. Or you can use your spindle lock and one bar.

Those jaws are really not made for deep work. Spigot jaws are. Also the 50mm jaws are not dovetailed on the inside, they have a lip. The instructions tell you, in capital letters, to not cut a dovetail with those jaws. They are made to bite into the wood.
The graphic below shows what will happen if you cut a dovetail on a spigot. Note: The outside of the jaws are dovetailed. Attached also is a photo of the inside; the total width of the “lip” is only about 1mm and only 4mm long. It’s easy to glance at the jaws and your eye picks up the outside dovetail and assumes the inside is the same.

[attachment=3277]
[attachment=3278]


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## kweinert (Mar 21, 2012)

rbaccus said:


> are you away having medical care?good luck



No, just a viral thing. Feeling better today but it's still too long of a drive to go in to work, if you get my meaning.

Thanks for the kind words though.


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