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Where does the tool go?

T

Tom Cadwalader

Joined
Nov 17, 2009
Messages
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Location
Cheboygan, MI
Maybe I should post this on the Newbie forum, when you get a catch on the outside of a turning with a bowl gouge where does the tool go? It seems to appear to me that the tool (and the guiding hand) are first lifted up then back down slamming on the tool rest sometimes. Fotunately I don't have tons of experience with catches, but after experiencing one the other day and trying to figure out what I did wrong I was trying to understand the dynamics of what was going on. I can see the track of the gouge digging deeper until it's ejected. But where does it go after that? It all happens so fast it's pretty hard to tell.
I haven't been able to find any video of this on the internet, that would be interesting in the context of understanding on a deeper level.
 
Tom, I don't think there is any rule to know where your tool will go after the catch has already happened. There are so many variable contributing factors that it would be impossible to come up with one. To my way of thinking, it's about as predictable as knowing which way a football will bounce after it hits the ground.....! o_O

Knowing the "why" a catch happens, is much more predictable. Basically, the tool cutting edge is driven under the wood's surface, because the tool shaft, or shank is forced to rotate on it's longitudinal axis.......or it moves on a fulcrum, sort of like a child's seesaw......or, a combination of the two.

edit: I did have a catch once, when I was holding the tool off the tool rest, in one hand, while I was looking somewhere else. I accidently ran the tip of the tool into the workpiece......stupid stuff! The only thing predictible about that, was how embarrassed I felt! :oops:

ko
 
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Richard Raffan has a short video that explains catches very well. It's on Fine Woodworking. You may have to be a subscriber to view it. Covers catches on spindles as well as bowls. Search for "Understanding Woodturning Catches".

Lyle Jamieson wrote an article on catches for American Woodturner, "Woodturners Fear Factor" (Winter 2006). Also, references from the AW index:

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Hope this helps.
 
Thanks, it does a good job of explaining the " how they happen". I am trying to figure out why the back side of my hand gets banged.
As in this video, I expect the tool to kick somewhat straight back, but in the two bad ones I have had over the course of 3 -4 years, it seemed like the tool and maybe my hand went up and the back down hard?
 
Tom,

When using new tools for the first time, several of the wood turning tools have a tendency to
catch easily if you aren't aware of the potential of the tool to catch the wood when you approach
the wood at the wrong angle.
When using the roughing gouge and bowl gouges catching the wings of the tool will create enough
force to knock the wood blank from the chuck. if you are standing in the wrong location the chunk
of wood has the potential to cause great bodily harm if it hits you in a bad spot.
You need to focus on the ends of the wings and make sure your cuts stop before the wings catch
the inner corners of your hollow wood form. Losing focus while you are using a tool is another major
cause of tool catches.
 
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