# Uh, Houston we have a problem...



## thrainson (Mar 24, 2015)

So after this happened for the second time in a row,I think I may be doing something wrong.



I was just doing a couple final touches on the inside bottom (needed to go a little deeper), and wham! it blows apart ! Am I doing something wrong?
Was using the 1/2" round EWT tool.
Thanks for any advise, or condolences lol!


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## ripjack13 (Mar 24, 2015)

Need some background info...
What speed were you at?
How did you have it attached?
Is it dry or wet wood?
What kind of wood is it?
Did you notice any chatter in the tool?
What's the depth of the cup, and how long is your tool?


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## ripjack13 (Mar 24, 2015)

Oh man....that last one looks bad....

Reactions: Funny 5


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## duncsuss (Mar 24, 2015)

Once you've thinned the stem, don't go back inside the bowl. There'll be too much flex in the stem, a catch is virtually guaranteed.

Or, putting it in positive terms, the sequence should be:

1) shape the blank into a cylinder
2) mark with a pencil where the bottom of the bowl will be, any features/accents on the stem, where the stem meets the foot, and where you're going to part it off
3) shape the outside of the bowl, but don't narrow it down to the stem, just start that curve and leave plenty of meat
4) sand the outside of the bowl and the rim
5) hollow the inside
6) sand the inside
7) if you have to go back into the inside for any reason, do it now
8) inch at a time, thin the stem, sand that section
9) shape the foot and sand it
10) part it off

YMMV, IMHO, etc ...

Reactions: Like 1 | Thank You! 1 | Agree 2 | Great Post 1 | Informative 3


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## thrainson (Mar 24, 2015)

ripjack13 said:


> Need some background info...
> What speed were you at?
> How did you have it attached?
> Is it dry or wet wood?
> ...


I was at 6 or 7 out of 10.
Attached with a 4 jaw chuck
10% on the wood
Black walnut
Well it moved when the cup blew up... Before that no.
The cup is 4" from rim to stem, I was working at about 3.5" The tool is wood ticks I believe it's 12"s but not 100% sure on that. Can check tomorrow.


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## thrainson (Mar 24, 2015)

duncsuss said:


> Once you've thinned the stem, don't go back inside the bowl. There'll be too much flex in the stem, a catch is virtually guaranteed.
> 
> Or, putting it in positive terms, the sequence should be:
> 
> ...


Thanks! Very helpful, I did go back in after doing the stem on both cups that blew up! That was probably what I did wrong. 

Here is one I just finished

Reactions: Like 5 | Way Cool 2


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## duncsuss (Mar 24, 2015)

thrainson said:


> Thanks! Very helpful, I did go back in after doing the stem on both cups that blew up! That was probably what I did wrong.


I've blown up bowls by going back to work on the rim area after I'd thinned the walls all the way down to the bottom. Once the walls are thin, there's simply too much give in the wood, and even a very light touch with the tool causes chatter and "tool bounce".

Same effect with a goblet -- the tool touches, the pressure causes it to deform, then it starts to vibrate and screech at you ... and it's all over before you know it.

This one looks much better -- red cedar?

Reactions: Thank You! 1


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## thrainson (Mar 25, 2015)

Yes, red aromatic cedar, I just love the smell of cedar chips!

Reactions: Agree 1


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## JR Custom Calls (Mar 25, 2015)

Using the side of a round cutter is the best way to get a catch. not sure why...

Reactions: Thank You! 1 | Agree 1


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## jmurray (Mar 25, 2015)

4" seems to be about the limit that I can get from the tool rest when hollowing. I use carbide cutters also. After 4" a catch or at least decent tearout seems inevitable.

Reactions: Thank You! 1


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## Schroedc (Mar 25, 2015)

I had the same issue when I was learning to turn thin pins and finials, as mentioned, once the stem is turned, don't go back inside or out towards the unsupported end. I have occasionally had a piece I had to do that with and I used a spindle steady with three rollers to support the piece and took really light cuts but that is usually a last resort for me.


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## duncsuss (Mar 25, 2015)

JR Custom Calls said:


> Using the side of a round cutter is the best way to get a catch. not sure why...


Physics 

If you're using the nose of a round cutter, it generally means you're pressing towards the headstock and cutting straight into the piece. Any vibrations make the point where you're cutting move up and down, which is kind of chattery but doesn't really impact the depth of cut.

If you're using the side, however, the vibrations are going to move the piece in and out against the cutter. What started as a light cut oscillates between no-cut at all and a deeper cut ... blammo

Reactions: Thank You! 1 | Agree 3 | Great Post 1 | Informative 1


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## vsauder (Mar 31, 2015)

I suppose "blammo" is a technical physics term?

That makes sense. Never thought about it that way.


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## duncsuss (Mar 31, 2015)

vsauder said:


> I suppose "blammo" is a technical physics term?



Well, not exactly -- it's a loose translation of the German technical term "flippenfloppenvibbelvobbelblammkaput"

Reactions: Funny 10 | Informative 1


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