What's Wrong With My Turning Tool?

[crokett]

I made myself a bent hollower/undercut tool. I have a small sorby - 3/8" round steel but wanted something larger and longer. I used 1/2" square steel and did the bend in my dad's forge, then drilled and tapped for a screw to hold a carbide cutter. The cutter is 1/2" round. The problem is when I use the tool it wants to torque down instead of cut. The bend is about 5" long and half that deep. I have cutter lined up with the straight part of the steel as best I can. I am wondering if a) it is off or b) the bend is too deep. However, in theory it shouldn't matter how deep the bend is, so long as the cutting edge is lined up with the long axis of the tool, no? The tool in question is the larger bent hollower in this pic. The smaller one is the Sorby that I put a new handle on. I am also wondering if I need to relocate the cutter on the tip. I can post a close-up if I need to.


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[Phil S]

It is hard to tell from the photos , but it appears that the Sorby cutter is directly inline with the axis of the handle. The one you made seems a bit off to the right - I would decrease the radius of the bend a few frog hairs and that might make a difference

 

[aplpickr]

I agree with PhilS. Try holding the cutter at a ~45° angle at about 7:30 to 8:00. Try to get a copy of Hunter tools instructions for a similar tool. Are you using this on only end-grain?

 

[crokett]

No. The first project I tried it on was the second turning of an undercut bowl I roughed with the sorby. After that project I put a much longer handle on the Sorby but still wanted to make the larger tool.

I will look at the cutter head/axis alignment and seeing if I can bend it again.

 

[aplpickr]

Most of the carbide tools similar to yours are designed for end grain only. Also I believe that the straight section of shaft between the curved and the handle is much too long for the diameter of the rod. My wife hollowed 50 red maple Christmas ornament bells (2" diameter) before rotating her Hunter cutter to the first new edge. You will be hard pressed to find a good substitute for Hunter cutters. Fifty ornaments @$25 times about 8 rotations for a new edge for about $21(for a new cutter) is hard to beat with a homemade tool and substitute cutter. There is a lot of very subtle engineering in and around the cutter on these tools that protect the brittle cutter and prevent it from taking too big a bite.

 

[woodArtz]

I'm certainly no tool expert, but I did stay in a Holiday Inn once.... Anyway, a couple of things that you might consider. The bent part must be beyond the tool rest or you will get a natural downward torque. Seems counterintuitive but that seems to work. Also, it seems to work better if you present the cutter to the wood at A less than 90 deg angle. Lyle jamieson talks about this in the linked article. https://www.lylejamieson.com/instruction-classes/documents/AAWArticle-FearFactor-Winter06.pdf

Hope that helps...

 

[crokett]

I played with it some tonight on the undercut bowl. I think it will work if I am careful with the presentation of the tool to the work, especially if I raise the handle of tool and present the cutter at a less than 90 degree angle. The cutters I am using are the same as on the Easywood Tools. I made a bent tool a tool with a square cutter and a tool with a round cutter. With the square cutter, a light touch and a shear scrape I can get a beautiful finish.