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Aggressive Long Wing on Bowl Gouge (Read 549 times)
 
Don Stephan
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Aggressive Long Wing on Bowl Gouge
Apr 28th, 2018 at 11:48am
 
Ever since I bought Richard Raffan's book and dvd on turning bowls, my favorite weapon for shaping the outside of bowls.has been a 1/2" bar spindle gouge, most often with a pull cut.  (I do not EVER use a spindle gouge inside a bowl.)

Yesterday I tried the same with a friend's 5/8"bar U flute bowl gouge with very straight wings at least 3/4" long, straight off the Oneway sharpening jig, on a 10" diameter black locust blank on a faceplate.  Pulling back from the tenon on a light cut and just starting to get round the corner, the long wing kept wanting to take a more aggressive cut/thicker shaving even though I was not pushing the cutting edge into the wood.  Went back to my spindle gouge and this did not happen, whether I took a light or medium cut.

How does one avoid this grabbiness when using a long very straight wing?
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Ed Weber
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Re: Aggressive Long Wing on Bowl Gouge
Reply #1 - Apr 28th, 2018 at 12:46pm
 
Short answer is to drop the handle and adjust left or right.
If you think of it like an X,Y,Z axis type of problem.
Lets say for this problem,
X is the rotation of the tool.
Y is the angle of the handle up and down.
Z is the angle of the handle left and right.
(assuming the tool handle in in a typical lowered position for a shear wing cut)
If your cutting edge/bevel angle (X) is the same, Y and Z remain.
Lifting the handle up and down will move the cutting edge to a different area of the wing, since the wing is 3/4" long, this will probably have little effect on your cut.
Moving the handle left and right will change the wing angle as the wood passes it.
I would suggest starting with the wing as close to vertical as you can and then slowly move the handle to the left. Increasing the angle until a comfortable amount of material is being removed, then try to move uniformly (moving your entire body not your hands) as you transition around the curvature of the bowl.
IMO This is easier done than said, Hope this wasn't too confusing.
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robo_hippy
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Re: Aggressive Long Wing on Bowl Gouge
Reply #2 - Apr 28th, 2018 at 5:15pm
 
I would have to see what you are doing, and see your '1/2 inch bar spindle gouge' to know what it is... A 'detail' type gouge is milled from round bar stock, and has a fairly thick body and shallow flute, and most of the time rather pointed rather than rounded. A spindle roughing gouge, old school version is flat bar stock that is heated and bent to a shape from ) to half round/circle. They have a tang rather than a long round shaft. Some of the newer SRGs are milled from round stock and a lot more sturdy than the forged versions.

With the swept back wing, you have a lot more metal you can put into the wood at one time, depending on tool presentation. With a 1/2 inch standard gouge with a 45/45 bevel/sweep (swept back gouges have sweep angles of 60+ degrees), you don't have nearly as much cutting edge that you can put into the wood. This could make it feel more grabby. Also, the black locust is harder than wood pecker lips... This could also make it feel more grabby. If you are rubbing the bevel at a high shear angle/handle dropped this is less grabby, as opposed to tool held level and doing more of a scraping cut, this can make it feel more grabby.
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Don Stephan
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Re: Aggressive Long Wing on Bowl Gouge
Reply #3 - Apr 28th, 2018 at 7:50pm
 
For shaping the outside of a bowl I am using a Thompson "standard" 1/2" bar spindle gouge.  (I can't find the chart showing the flute depth for the four different Thompson spindle gouges.) 

The signature Raffan bowl roughing spindle gouge was a 9/16" diameter bar, looking very much like any other "standard" spindle gouge, but has been discontinued.  I bring it to the wood in a very passive presentation - handle horizontal, primary bevel perpendicular to the surface of the wood, and the flute facing 9 o'clock, facing the wood.  In a smooth, fluid motion I am simultaneously rotating the flute to about 10:30 o'click, dropping the handle to about 45 degrees, and swinging the handle to the left so that the shaving is centered on the left wing (which is perhaps 1/2" long and slightly curved).  On woods like black cherry and walnut, I get a shaving about 3/8" wide with little effort, but on the black locust the shaving is thinner because the wood is harder.

With the 5/8" bar U bowl gouge with the long straight wings I was again bringing the tool tip to the wood in a very passive presentation, then making the same simultaneous three movements to a more aggressive presentation.  Pulling the cutting edge along the surface of the wood, I was getting a thin shaving about 1/2" wide, but then the cutting edge would seem to grab and take a slightly thicker shaving, leaving a shallow groove in the surface.  It could be cleaned up with a shear scrape taking very thin shavings, but that's extra work.

Those of you using the Oneway jig to sharpen a U bowl gouge with long side wings, are you leaving the wings perfectly straight or slightly curved?
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Ed Weber
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Re: Aggressive Long Wing on Bowl Gouge
Reply #4 - Apr 28th, 2018 at 8:18pm
 
Don Stephan wrote on Apr 28th, 2018 at 7:50pm:
Those of you using the Oneway jig to sharpen a U bowl gouge with long side wings, are you leaving the wings perfectly straight or slightly curved?


I leave a very slight convex curve
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Re: Aggressive Long Wing on Bowl Gouge
Reply #5 - Apr 29th, 2018 at 7:06pm
 
Today I found on Youtube a sharpening video by Doug Thompson, and he also leaves a slight convex curve on the wings of his gouges.  Seems like that should be slightly less aggressive than a perfectly straight wing.
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« Last Edit: Apr 29th, 2018 at 7:06pm by Don Stephan »  
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robo_hippy
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Re: Aggressive Long Wing on Bowl Gouge
Reply #6 - Apr 30th, 2018 at 10:07am
 
With Doug's V gouge, the wings, when ground with a slight arc, if you look at them head on, it gives a more 'parabolic' shape appearance to the flute. Not sure if it makes the gouge cut any different or not.

robo hippy
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Re: Aggressive Long Wing on Bowl Gouge
Reply #7 - May 6th, 2018 at 10:32am
 
Ed Weber wrote on Apr 28th, 2018 at 8:18pm:
I leave a very slight convex curve


Ed...Two questions for you.  I'm not quite understanding what you're referencing with the above.  Could you perhaps place your photo in PowerPoint or other like platform and 'draw' where specifically this 'slight...curve' is?

The second question is regarding the relief bevel...is there a particular cut you find this specifically useful or is it a technique you've adopted so as to not ride the bevel too hard?

THANKS...John
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Re: Aggressive Long Wing on Bowl Gouge
Reply #8 - May 6th, 2018 at 12:23pm
 
The relief 'bevel' is a geometry thing for the inside of bowls, or any concave surface. The idea is that the closer the cutting edge is to the bevel rubbing spot, the easier it is to control the cut. On the outside of the bowl or any convex surface, bevel angle and relief of the bevel really doesn't do anything because the bevel rubs right behind the cutting edge. It is a whole different thing on the inside of a bowl. If you leave the full length bevel on the gouge, that sharp heel makes the rubbing spot much farther away from the cutting edge, and can actually push the cutting edge into the cut, kind of accelerating the cut. It will also leave bruise marks in the wood which some times you can see as rings on the inside and you can sand through to the outside of the bowl and they don't seem to ever go away. The relief bevel provides no other function. I free hand grind mine and make the whole 'relief bevel' a rounded over thing rather than another sharp edge.

As for the bevel rubbing part, "The bevel should rub the wood, but the wood should not know it." Far easier said than done. With roughing cuts, it doesn't make any difference, other than if you need the practice this is where you learn how little pressure is needed to let the cut proceed. With finish cuts, you have to let the wood cut gently rather than having to push on the tool. This is a sensitivity thing, where you have to learn to feel it, and it really isn't some thing you can measure. If you are pushing too hard, especially on thinner pieces, you will distort the wood as it spins which makes every thing more difficult.

As near as I can tell, with bevel angles, I prefer a 45/45 grind for most of my bowl work. This is a platform sharpened gouge with 45 degree bevel and 45 degrees of sweep and roll. You can't quite get the same grind with gouge jigs because they roll more and you end up with a more 'acute' grind on the wing. A more acute wing doesn't make a whole lot of difference to me since I cut more with the nose of the gouge rather than the wing. There are many who prefer a 40/40 grind, but that feels more like a detail tool and/or combination tool rather than the specialized tool. Main advantage is that it takes less pressure to push it through the cutting action. I hadn't considered that till I heard Stuart Batty mention it, or maybe it was Mike Mahoney... They also commented that it takes more effort to push a 60 or more degree bevel gouge through the wood when compared to the more acute angles. After playing around with that over a period of time, it seems to hold true to a noticeable degree with heavy roughing cuts, but not much difference with finish cuts where you have to be dainty. The 45/45 is better for going down the sides, but lousy for making the transition and going across the bottom unless it is a shallow bowl. The 60 and 70 degree bevels are better for the transition and going across the bottom especially in deeper bowls. So, the 45/45 is more of a specialized tool, and the 60 degree swept back wing is more of a multiple use tool... I have tried this with just about every flute shape I can find, and results are pretty much the same.

robo hippy
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Ed Weber
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Re: Aggressive Long Wing on Bowl Gouge
Reply #9 - May 6th, 2018 at 12:33pm
 
robo_hippy wrote on May 6th, 2018 at 12:23pm:
The relief 'bevel' is a geometry thing for the inside of bowls, or any concave surface.


Thumbs Up

John Grace wrote on May 6th, 2018 at 10:32am:
Ed...Two questions for you.  I'm not quite understanding what you're referencing with the above.  Could you perhaps place your photo in PowerPoint or other like platform and 'draw' where specifically this 'slight...curve' is?


I was referring to the cutting edge of the wing.
The edge does not come straight back from the tip, it has a slight convex cure to it.
I will try to provide a better photo and/or drawing (as soon as I can) to clarify for anyone who is interested.
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Don Stephan
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Re: Aggressive Long Wing on Bowl Gouge
Reply #10 - May 6th, 2018 at 5:18pm
 
John

When a gouge is resting on a table, and the thickest part of the gouge is closest to the table, a straightedge across the sides of the gouge is perfectly horizontal.  This position is often called "flute up" or "flute facing 12 o'clock if one is looking along the tool from handle to cutting edge.  When the gouge is "flute up" in a side view the cutting edge rises from the nose or tip of the gouge to the side of the gouge in a convex curve.

The picture Ed graciously included is not a perfect side view as it is looking down slightly, but this convex curve is visible, especially on the back side, along the cutting edge from the nose/tip to the end of the cutting edge.

I have also found a narrower primary bevel can reduce drag and chatter moving down from the rim on the inside of a bowl, even before reaching the transition area from side to bottom.
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Ed Weber
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Re: Aggressive Long Wing on Bowl Gouge
Reply #11 - May 6th, 2018 at 7:31pm
 
Don Stephan wrote on May 6th, 2018 at 5:18pm:
The picture Ed graciously included is not a perfect side view


Aren't we picky  Grin
Actually the photo I provided shows the curvature better than a direct on side view, since you can see both the inside and outside.
Looking at the profile of the right wing, it clearly shows a curve from the nose all the way to where the wing ends meeting the flute.

If you need or want a different photo, let me know and I'll see what I can do.
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Re: Aggressive Long Wing on Bowl Gouge
Reply #12 - May 7th, 2018 at 6:53am
 
Thanks all...I think I get it now.
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Re: Aggressive Long Wing on Bowl Gouge
Reply #13 - May 7th, 2018 at 7:08pm
 
Actually, I think it is an excellent picture!  I'm still struggling for verbage to describe a "fingernail grind" and was worried it might be confusing to talk about a side view in relation to your picture, which while excellent is not exactly horizontal to the gouge.
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