Demo on cutting with 3 bowls gouges

[Bob Bergstrom]

This is a link to the demo I did for the Windy City Woodturners in Lyle Illinois. I talked about clean cutting characteristics outside and inside the bowl using three different bowl gouge profiles.


http://youtu.be/Ufs7O5aRbsY

[Steve Schlumpf]

Bob, I think you gave a really good demo and your video of the different gouges being used on a bowl really highlights their differences. Thanks for sharing!

[robert baccus]

great and informing for sure yeah.

[Justin Stephen]

Great video, thanks!


This is a link to the demo I did for the Windy City Woodturners in Lyle Illinois.

Lisle. :) Went to high school one town north.

[David Cramer]

Wow Bob, great presentation! You explained things very, very well. Both outstanding oratory and turning skills:) Congrats and thanks for posting!

David

[Reed Gray]

I am going to have to watch this several times more. Main reason is that we are so different. Mostly, I always have my tools rolled away from the wood at 45 to 90 degrees, and you tend to have the flutes more vertical. I do favor the more open fluted designs, with little sweep to the wings. I never cut with the wing on the uphill side, which to me presents a higher risk of catching, especially on the inside....

robo hippy

[Bob Bergstrom]

I am going to have to watch this several times more. Main reason is that we are so different. Mostly, I always have my tools rolled away from the wood at 45 to 90 degrees, and you tend to have the flutes more vertical. I do favor the more open fluted designs, with little sweep to the wings. I never cut with the wing on the uphill side, which to me presents a higher risk of catching, especially on the inside....

robo hippy
Reed I don't always work with the wings up. If I'm moving waste wood I will use the leading edge when cutting the inside of the bowl. On the outside a lot of pulling cuts. I think part of my cutting on the trail edge is due to a rather vertical shapening of the wings on the swept back gouges. They don't seem to catch as a tool with more of a roll over grind. It seem my gouge can't ride in the trail wing without rolling into the surface of the bowl. To get a gouge shapening on a jig it seems one would have to roll the tool toward 11:45 on a clock. Just my thoughts.

[Reed Gray]

Well shucks, I wish we could do a play date.... Where are the transporters when you need them??? I remember a comment in your clip some where about the nose cutting, and the wing scraping, which is a conclusion I came to a while ago, the nose is at a shear angle, and the wing is at a scraping angle. I did notice that none of your gouges have the swept back wings on them, and I don't use them either. I do all of my bowl roughing with scrapers too, using gouges only for finish cuts. With the free hand platform sharpening that I do, I do roll my flutes over maybe a bit past 90 degrees/3 or 9 o'clock.

Hope to run into you some day. I will be in KC for the Symposium in 2017, maybe then. Don't think I will have a lathe with me though.... I do have family in the area.

robo hippy

[Bob Bergstrom]

Reed
interesting idea. A play day at clubs with multiple lathes. I know the Chicago Woodturners have six Jet 16 x 42s and a 3520 that are only used for hands on lessons when turners come to Chicago for demos. The Illiana Club has multiple lathes in their workshop. Exchanging idea sure beats watching a pro put on his show. Especially with access to a iPhone slow motion. The last two generations of Apple TV allows showing the replay on flat screen tv without a wireless system. It is called conference mode. A group could turn and review in slow motion like instant replay on tv
I do have gouges that are ground back a 1 1/2" with a very narrow nose ( shaped like a crockadiles snout ). The wings at the nose are minimal in height.
The magnetic flags on the flutes show how the cutting action increases as the flute is rotated to near vertical. I had very little pressure from on the tool handle so the feed rate was creating mostly fluff to small curls.

[Reed Gray]

I don't understand how flutes more vertical makes for 'increased' cutting action. Nose design, for sure plays into it, and how hard you are pushing on the handle. Nose design also determines how high of a shear angle you can get. So, 45/45 grind (Batty 40/40 is too pointy for me) and most other grinds are an easy 45 degree shear angle. Doug Thompson's fluteless gouge, or a spindle/detail gouge with a ) nose shape is easy to get 70 or more degrees shear. I am really focused on the shear angles for cleaner cuts... I have found the bottom feeder types with a half circle flute shape can roll over on the side and get a 70 or so degree shear angle, but if I have the flutes up, then 45 is closer. Note on shear: scraper flat on the tool rest = 0 degree shear angle. Swept back grind gouge on outside of bowl with handle way low, and cutting with the wing is a 70 or so shear. Inside of bowl you need much less pointy nose and more round nose and flute to get the higher shear angles since you can't drop the handle. I can see that cutting with the uphill/side against the wood wing on the inside of a bowl works, but don't understand how it works the way it does.

robo hippy

[Bob Bergstrom]

I don't understand how flutes more vertical makes for 'increased' cutting action. Nose design, for sure plays into it, and how hard you are pushing on the handle. Nose design also determines how high of a shear angle you can get. So, 45/45 grind (Batty 40/40 is too pointy for me) and most other grinds are an easy 45 degree shear angle. Doug Thompson's fluteless gouge, or a spindle/detail gouge with a ) nose shape is easy to get 70 or more degrees shear. I am really focused on the shear angles for cleaner cuts... I have found the bottom feeder types with a half circle flute shape can roll over on the side and get a 70 or so degree shear angle, but if I have the flutes up, then 45 is closer. Note on shear: scraper flat on the tool rest = 0 degree shear angle. Swept back grind gouge on outside of bowl with handle way low, and cutting with the wing is a 70 or so shear. Inside of bowl you need much less pointy nose and more round nose and flute to get the higher shear angles since you can't drop the handle. I can see that cutting with the uphill/side against the wood wing on the inside of a bowl works, but don't understand how it works the way it does.

robo hippy
I just looked through my videos on iTunes and if you can get a copy of Ellsworth DVD on bowls he shows his finish cuts on the inside of the bowl with his grind. Mike Mahoney also uses his 3/8" "U" gouge running the left wing for the cut. It is exactly what I was doing in the video. The point I was referring to with the wing more vertical is that when I grind them on my CBN wheel, the flute is close to straight up and swung to the center of the nose while dropping the handle. The result is a thinner cross section of the wing more like a knife than an axe. The heal of the side wing is more in line vertically with the edge. Consequently the wing has less of a heal protruding against the bowl. The only parts that are touching the wood are just to the left of the nose and the what is left of the nose bevel just below it. I can take some pics of the gouges if necessary.

[Bob Bergstrom]

Here's 3 pics of swept back grinds. The first is a3/4" "V". The second is a 1/2" parabolic. The third is a crockadile grind with extremely swept back wings. All three have a reduced heal under the vertical side grind.
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