# Persistent offcenter - trying to sort out what I'm doing wrong



## kweinert (Apr 23, 2012)

I think I'm catching on and slowly improving - then all of the sudden it's getting warmer and I'm trying to figure out why I'm in this basket . . .

In building the wood rack this weekend I ran across a piece of butternut that was about 2 1/2 x 6 x 12. I had planned on cutting it up for my puzzles but that piece suddenly looked like a couple of bowl blanks.

So I cut it in half and now have two 6x6 bowl blanks. I rounded them off on the bandsaw to make it a bit easier to get started.

Marked the center of one, drilled the hole for the woodworm and mounted the blank on the lathe.

Now, i expect it to feel a little 'off center' while I finish up the rounding, but for this blank it never goes away. Even while turning the bottom flat and starting to put the tenon on it you get the pulsating feeling all the way to the center.

Maybe I have always just had poor technique and it wasn't that noticeable until I got something bigger. Could tools that need to be sharpened cause this?

Any thoughts and/or suggestions will be greatly appreciated. Thanks to all for your contributions.


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## Spa City Woodworks (Apr 23, 2012)

I've had something similar happen a couple times in the past... in one instance I'd drilled a pilot hole too big for my wormscrew and it had stripped out. The pilot hole then became elongated and threw the blank into an eliptical spin. The tailstock was attached which kept it from probably flying across the room. A 12" round blank became an 8" blank before I figured it out. It was not my finest hour. :dash2:

Is your blank a sapwood/heartwood combo piece. Sometimes the sap is more present on one side.


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## kweinert (Apr 23, 2012)

Spa City Woodworks said:


> I've had something similar happen a couple times in the past... in one instance I'd drilled a pilot hole too big for my wormscrew and it had stripped out. The pilot hole then became elongated and threw the blank into an eliptical spin. The tailstock was attached which kept it from probably flying across the room. A 12" round blank became an 8" blank before I figured it out. It was not my finest hour. :dash2:



That I know I've not done. 

This time.



Spa City Woodworks said:


> Is your blank a sapwood/heartwood combo piece. Sometimes the sap is more present on one side.



[attachment=4697]

You can see in this picture that the side showing is real rough - the 90 degree opposing sides are real smooth. This, to me, doesn't look like it fits what you were describing - am I wrong?


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## kweinert (Apr 23, 2012)

bigcouger said:


> :morning2: I had the same problem at one time couldnt figure it out so i stopped for a day, next day sharpened the tools and redid the tenden again an it was fine so I think its the tools need to be sharp an it cuts an not ride the surface.



I'll have to wait until tomorrow as well. Starting to get a touch late here to be making that much noise. I'll be glad when I'm back out into a private garage on a busy corner where the traffic will make more noise than I do :)

Thanks for sharing your experience.


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## DKMD (Apr 23, 2012)

I'd try bring up the tailstock and sharpening the tool. If you don't want to leave a mark on the butternut, you could face it off and add a glue blue... Then create a tenon on the glue block and mount it in the chuck. 

The other thing I'd try is making my cuts in the opposite direction from what you've been doing... Even though the grain is running perpendicular to the ways, sometimes I'll get a cleaner cut just by cutting in the opposite direction(ie. left to right if I've been struggling right to left).


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## DKMD (Apr 24, 2012)

I read Bob's reply and then my own again, and I realized how confusing my response was/is. He's right about cutting downhill when forming the bowl shape! When I was talking about cutting both directions, I was talking only about the cuts taken to true up the blank. Ok, I feel better now!

Also, a shear cut or shear scraping cut on tear out prone wood is a great technique for me... I'm not even gonna try to explain that in text, but I'd be happy to show you if you drop by the shop. Seems like there may be some decent YouTube video on the topic as well.


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## Mike Mills (Apr 24, 2012)

Unless you have a dedicated screw chuck, check the jaws (for mounting tightness) on your scroll chuck. If one, or more :dash2: jaws are loose it will cause this. 
You also need as flat an area as possible for the jaws to seat against. I use a 3 1/8" forstner bit.

To me, just from your picture, it is end grain tear out. It appears you rounded the entire outside first? It is much easier to place your tool rest at 45* and keep taking off bits to form the bowl shape; the outside will get round on its own. You _can _work from the outside diameter down but you will get smoother cut (supported wood) by always working from the smallest diameter to the largest. (The opposite is true for spindle turning).


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## Dane Fuller (Apr 24, 2012)

Looks like tear out to me. Super sharp tools, highest speed you feel comfy with and lite cuts might help. Doc brought up my least favorite but most used technique. The shear cut and shear scrape, IMHO, are two techniques everyone should know. That will get rid of 90% or more of your tear out.

Google Bob Hamilton and watch his shear cut/scrape videos on youtube. He's got about 200 on there. I've seen all of them and still go back and get refreshers.


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## kweinert (Apr 24, 2012)

Mike Mills said:


> Unless you have a dedicated screw chuck, check the jaws (for mounting tightness) on your scroll chuck. If one, or more :dash2: jaws are loose it will cause this.
> You also need as flat an area as possible for the jaws to seat against. I use a 3 1/8" forstner bit.



I'll check the jaws. Also, i presumed that this was already flat. It *seemed* flat, but I could be wrong about that.



Mike Mills said:


> To me, just from your picture, it is end grain tear out. It appears you rounded the entire outside first?



That would be a correct observation.



Mike Mills said:


> It is much easier to place your tool rest at 45* and keep taking off bits to form the bowl shape; the outside will get round on its own. You _can _work from the outside diameter down but you will get smoother cut (supported wood) by always working from the smallest diameter to the largest. (The opposite is true for spindle turning).



Learn something new every day. Thank you.


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## kweinert (Apr 24, 2012)

Dane Fuller said:


> Looks like tear out to me. Super sharp tools, highest speed you feel comfy with and lite cuts might help. Doc brought up my least favorite but most used technique. The shear cut and shear scrape, IMHO, are two techniques everyone should know. That will get rid of 90% or more of your tear out.



I could be turning a bit too slow. Bigger and heavier (and I know this is neither all the big nor all that heavy to most of you folk :) still makes me a bit nervous. I could have sped it up since I pre-cut the circle on the bandsaw before mounting it up.



Dane Fuller said:


> Google Bob Hamilton and watch his shear cut/scrape videos on youtube. He's got about 200 on there. I've seen all of them and still go back and get refreshers.



Thanks for the hint.


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## kweinert (Apr 24, 2012)

Well, with the assistance of the kind folk here and me recovering from a case of cranial-ass inversion, it's looking better today:

[attachment=4716]

[attachment=4717]

This is after a 60 grit sanding. You can still see a bit of the open grain issue but it's pretty much cleared up.

The bit of advice on checking to ensure that all the chuck jaws were tight was a good one. Oh, the jaws were tight - but they were the wrong ones. I had just been working on a peppermill and had used the pin jaws to fit inside the opening and left those on. 

Clearly this provides a pretty small surface for stabilizing the blank.

That and I sharpened my tools. And kicked up the speed a bit.

I was operating in the Perfect Storm of Stupidity and wondered why I was having a problem.

Thanks again to all who offered advice. That's my only saving grace - maybe someday I can help someone else past their stumbling block.


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## Dane Fuller (Apr 24, 2012)

Looks like you really have it working now. The shear scrape technique will take care of more of that tear out and the tool marks. Then you won't have to sand as much.....!


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## Mike1950 (Apr 24, 2012)

I do not turn but reading this has been very interesting. Seeing the tutors teach the student and watch the improvement is very impressive. Thanks student and it is looking great and thanks teachers- You guys are great...............


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## Mike Mills (Apr 26, 2012)

Looking good!
Dane is right, a few passes in a sheer scrape mode should remove the torn out grain and tool marks. Tool marks are fairly easy to sand anway; torn grain is a bugger. Often I cheat, sand with oil, and allow the slurry to fill the torn grain. No one ever knows, sorta like Pore-O-Pac for woodturning.


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## kweinert (Apr 26, 2012)

rbaccus said:


> Mike Mills said:
> 
> 
> > Looking good!
> ...



Because I don't have any 40 grit - sounds like I should though :)

At any rate, here's the completed bowl:

[attachment=4827]

[attachment=4828]

Once again I get a little eager to get it finished so it's not as clean as it should be (but I angled the bowl so that part is harder to see )

This one I put a tenon on then used a jam chuck to turn off the tenon - another first for me.

The wall to bottom transition is much better and the thickness is pretty good (for me - not ready to make lampshades from NIP yet though.)

Thanks again for all of your assistance and advice. I should put this in a SFRB and pass it around for you all to sign.


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