Undercutting the core

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Undercutting the core

Postby nnykamp » Tue Apr 10, 2012 4:33 pm

I've got a problem I'd like to pose to you all:

I've turned a few bowls, some small ones of birch, and now a larger one of ash. In both cases, undercutting the core is not going well at all. I'm having a terrible time with the hook catching. It seems as though there is no happy medium between the hook sliding across the wood, and then when it does engage, it hooks. I've tried skewing as much as possible, and trying different locations on the core. My thought is that as the diameter of the core shrinks the hook no longer has anything to ride on, and the edge of the hook dives down. My hooks are mostly outside bevel. I'd love to visit someone who knows what they're doing to get an idea of what I'm doing wrong, but the nearest person I know of is Mr. StoneDahl, who is fully 350 miles away. (maybe a family vacation to northern Wisconsin is in order)
Your thoughts and suggestions would be greatly appreciated.
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Re: Undercutting the core

Postby Sharif Adams » Tue Apr 10, 2012 10:41 pm

Hi, not sure which way you are holding the hook, ie tip up or tip down. Have you seen the Ben Orford you tube video series 'turning a bowl'. The fifth part of the series at 3.20 (ish) shows one way of undercutting the core. I've just been looking online and as far as I can see from a basic search, this is the clearest explanation/demo of a straightforward way of undercutting the core that I could find.

I find a hook with the bevel on the inside better for undercutting the core, but that's just me. I also find the very slightest difference in angle where bevel meets core can make a massive difference,(I'm sure you know that already), and getting it started can sometimes be a case of holding back more than seems at first required, but once going I often tend to bully the core quite aggressively! I'm sure there will be people with more helpful advice (and more experience) along soon to help. Good luck with it.
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Re: Undercutting the core

Postby jarrod stonedahl » Wed Apr 11, 2012 5:23 am

hey, i had the same problem when starting out......it's really tough to explain, as was told to me when i asked the same question here. i agree with sharif on the hook bevel as well as holding back....tight grip/complete control of the tool are very important. are you forging your own hooks? if so make one with very small hook....1/8-1/4 inch radius will help too. keep trying,don't give up, put your critical mind on it, and reduce as many variables as possible as you learn. you will get it....it does take time and more than a few bowls to really get it without one on one instruction. i have not seen the video..but watch all the videos on youtube with the pole lathe bowl turning. you are more than welcome to come up some time, that's bit of a drive. good luck wish i could explain it in more detail.
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Re: Undercutting the core

Postby nnykamp » Wed Apr 11, 2012 6:35 pm

Hey, thanks for the pointers, the Ben Orford series looks to be a gold mine of information. I have been forging my own tools from OCS, and right now they're all about 3/8." I've been pretty happy with how they work outside the bowl, but I can see that a smaller tool would have less grab. I'm making a run to the local tree dump today, see if I can find some fresh birch to mess with.
Thanks again!
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Re: Undercutting the core

Postby Paul Thornton 2sheds » Wed Apr 11, 2012 8:01 pm

nnykamp wrote:see if I can find some fresh birch to mess with.


it has been some time since i turned a bowl, i have been waiting for my big lump of birch (an entire tree) to "mellow". very green wood is not so nice to use due to 1) it being much heavier to spin 2) the final finish is not so good, it can be a bit fluffy or raggy

all the best
Paul
learning more every day
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