What's your favorite technique for hollowing a bowl?

[John Hicks]

As with most bowl hollowing; I seem to have a bit of a problem not getting tool marks on the top inch or so of the rim. I have tried many ways of hollowing a bowl over the years and seem to get those ridges quite often. They require lots of sanding. I've tried the "leave a hump in the middle" technique and it always seems to get in the way of the gouge sweeping motion.

 

[Monty Ivy]

I march the hollow out. Left, right, left, right

 

[Richard Coers]

The most common error on leading into a bowl is to not have the bevel parallel to the outside wall. It feels unnatural to have the end of the handle that far towards the center of the lathe, that so many don't move it over far enough. Put a little 6" scale on the bevel and just set it on the tool rest with the lathe shut off. Look at how far you have to take the handle over to make the bevel 90 degrees to the face of the blank. Having the flutes in the proper orientation is the second most common. I have the flutes at 90 degrees and then after the cut starts, roll it to 45 degrees.

 

[hockenbery]

As with most bowl hollowing; I seem to have a bit of a problem not getting tool marks on the top inch or so of the rim. I have tried many ways of hollowing a bowl over the years and seem to get those ridges quite often. They require lots of sanding. I've tried the "leave a hump in the middle" technique and it always seems to get in the way of the gouge sweeping motion.

I use a technique Jimmy Clewes taught is a club class here.
I use a 1/4” gouge (3/8” bar) for that first inch.
That forces a small cut and the small gouge is little bit sharper and attention to lining up the bevel with the outside wall.
I use a Michelson grind. Jimmy used a traditional grind with a 45-40 degree bevel

I show this technique in the greenwood demo. The video of returning a dried bowl
I get a nice surface with the Ellsworth gouge but then an extra nice surface with the small gouge.

Working with green wood

The August 2015 AAW JOURNAL has great article by David Ellsworth on working with green wood. This is followed by 11 marvelous ways turners turned cracks into features. One of David's themes is that the deck is stacked against newer woodturners successfully working with wet wood. Might be a nice...

www.aawforum.org

 

[hockenbery]

These gifs will give you a look
This is the Ellsworth gouge see the small cut:




This is the 1/4” bowl gouge smaller cut:

 

[Brian Gustin]

WHat I learned to do is, sight along the bevel of your gouge and point that imaginary line in the direction you want to cut.

 

[Odie]

I turned a very dry and dense African Blackwood bowl the other day. This, according to the wood database, is at the top of the list for Janka hardness.....right up there with Lignum Vitae!

"African blackwood is considered to be among the hardest and densest of woods in the world; indeed, among some 285 species tested, (including Lignum Vitae), Gabriel Janka originally found African Blackwood to be the very hardest."

African Blackwood | The Wood Database (Hardwood)

www.wood-database.com

I purchased three bowl sized blocks of African Blackwood for a little over $600 a few months ago. They are sourced from the estate sale of a musical instrument maker. I've never seen this wood in any size large enough to make a bowl, but all of these are approximately 8" square. These have been in storage for decades, I think.....because the moisture content is very low.

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This is my opinion.......those having trouble making bowls are 99% likely to not have the sharpest tools they could have......and, probably less than 1% of turners these days are hand honing their gouge cutting edges. This is true, even for those who swear up and down that their gouges are "scary sharp".....and, I dare say there are a few "advanced" turners on that list!

-----odie-----

 

[David Wrate]

@odie Coming from the world of flatwork where I sharpen my chisels and plane blades to 16,000 grit on a ceramic 'stone', only sharpening turning tools to 180 grit or 600 grit doesn't seem nearly sharp enough.
Not wanting to open the proverbial can o' worms but is it because when turning a keener edge needs to be sharpened more frequently?

 

[Ron Solfest]

As others have said: keep your gouge sharp, and visualize the line from the bevel entering the top of the inside cut at 90deg and then quickly going parallel to the outside shape.

I typically step down, hogging out about an inch depth at a time and getting very close to final surface (within ~1/16”). Then with a sharp gouge clean up that last bit and hog the next section. Start just before the new clean up and blend it it.

I’m not afraid to stop the lathe and feel the shape and thickness often. A small ‘hump’ can be smoothed out with a shear scrape (if you sharpen with a slight crown along the side), but be careful to keep the shear scrape *shear*…if you get too close to perpendicular to the rotational direction a bad catch will result and a broken bowl if you’re already thin and try to go back more than one or two step sections (a thin rotating bowl will be flexing from the centrifugal force, as well as the force of the cut changing from side grain to end grain).

As mentioned, I’m not afraid to stop the lathe and check. I’m retired and turn for fun, I don’t have to put out production quotas or force a situation I’m not sure of to save time.

Oh, and make sure to grind off the heal of the gouge. Otherwise it gets in the way on the concave curve and ‘bruises’ the wood.

Practice makes perfect, I have yet to achieve the perfect bowl but I keep trying and generally each one addresses issues from the last

 

[Dean Center]

John, are you making bowls with an undercut rim? If so, that is very hard to cut without some residual tool marks. Turning the inside 'downhill', or "from big to small", means that the part just below the rim needs to be cut from the widest interior dimension out to the rim, rather than from rim in. Not easy to do.

In any case, 2 things that have helped me, in addition to the good tips above, are:
1. Cut out just enough of the interior to access the first 1 1/2" of the side. Leave more than just a post in the center of the bowl. Once you've got the first part of the side hollowed to your satisfaction, continue hollowing as usual. I believe Glenn Lucas shows this approach in his bowl teaching. If this works for you, you can experiment with leaving less and less of the interior in place until you start to get marks again, then you'll know how much you can take out and still get a good surface.
2. A negative rake scraper, of the right size and with the right curve on the end, can nicely smooth out this area. It helps to support the outside of the bowl with a little counter pressure to reduce vibration when you do this. In fact, a little counter pressure with your left index finger while using a bowl gouge can make a difference, too.

 

[Odie]

@odie Coming from the world of flatwork where I sharpen my chisels and plane blades to 16,000 grit on a ceramic 'stone', only sharpening turning tools to 180 grit or 600 grit doesn't seem nearly sharp enough.
Not wanting to open the proverbial can o' worms but is it because when turning a keener edge needs to be sharpened more frequently?

Hello David.....

A comparison of chisels used for flatwork, and gouges used for turning is apples to oranges.

The sharpness of your flatwork chisels would be great for turning.....but, there are differences in how they are used for the two applications. A lathe tool sharpened to 600gt has the distinct advantage of speed. That lathe tool at a much higher speed will make a clean cut that is equal to a flatwork chisel sharpened to a much higher grit.

There is something else to consider, too. Most all turners these days, go directly from their grinder to the lathe. The disadvantage of that, is the edge at a single point is ground in a single direction. When that edge is honed, the edge is created by using the stone, or diamond hone, in my case......in multiple directions. This multiple directions vs a single direction, actually creates a sharper, more refined edge, equal to doing it with a finer grit in a single direction.

You are correct in that the finer, more refined edge required for lathe work needs constant attention to keep the same level of sharpness. Many turners are using exotic steels to keep from having to deal with resharpening as often as I do......and, there are problems with that, too. Like many things, to gain an advantage, you have to give up something in order to get something. I use M2 steel for all my turning tools......mainly because I want the fine edge to dull faster than the equivalent edge using exotic steels! (I know that doesn't make any sense to a lot of turners......and, I have explained my reasoning for this elsewhere in the forums.....more than once.)

The only thing I have to back up my reasoning in these things.....are the results I am able to attain.

-----odie-----

 

[Brian Gustin]

@odie Coming from the world of flatwork where I sharpen my chisels and plane blades to 16,000 grit on a ceramic 'stone', only sharpening turning tools to 180 grit or 600 grit doesn't seem nearly sharp enough.
Not wanting to open the proverbial can o' worms but is it because when turning a keener edge needs to be sharpened more frequently?

Uh yeah as Odie mentions, there's those differences. And then.. consider , 10 inch diameter bowl travelling at 1000 RPM 10 x Pi (3.14) = 31.40 inches, multiply by 1000 = 31400 inches divided by 12 = 2,616 feet

2600 feet in a minute, I'd like to see you hand plane 2600 feet of lumber in one minute... ?

Try turning with a chisel honed to 16000 grit keenness , you lose the edge in mere seconds, and end up with something equivalent to perhaps 180 grit edge. There's Sharpness, which is gonna cut wood any way you slice it (pun intended) then there's Keenness, which defines how effortlessly the wood is cut....

you can sharpen a gouge to shave hair off your arm with a 180 grit CBN wheel (and a quick strop) without needing to hone further (I know, I actually tried it as I wondered how sharp 180 grit cbn was getting my gouges)

just IMHO.

 

[Randy Anderson]

For me I have much better outcomes if I work the bowl wall thickness on the inside downward an inch or so at a time. Don't move on and expect to just take long cuts from rim to bottom working the entire wall to the same thickness. I see that done a lot and hats off to the pros that can but I've had too many times when trying to come back to clean up the top couple of inches on the inside has made a mess. Stop, make sure the top 1-2 inches are clean, no chatter marks or tool marks, then move on to do the next 1-2 inches while you take inner mass out along the way. NR scraper to clean up then move on down. As you get toward the bottom it's easier to take those long passes all the way to center. The outer rim can move as it gets thinner, the mass removed can change the shape, etc and once you move on you can't always come back to the outer rim and expect it to spin perfect like the bottom 1/3 does.

 

[robo hippy]

Well, for me, after going down the first 1 to 1 1/2 inches on the inside of a bowl, I use a shear scrape to clean things up, and that is part of why I did a video just on shear scraping. A NRS works very well across the bottom of the bowl since there is no uphill/downhill grain in the bottom. Once you start coming up the side of the bowl, the NRS is still a scraper, and it will leave some torn grain in the uphill parts of the bowl. How much tear out there is depends on the wood. On soft maples, it is considerable. On some thing like madrone or pear or dogwood, tear out is very minimal. This is why I prefer a shear scrape from the transition to the rim of the bowl as my finish cut. Some times the gouges seem to work, some times they don't.

As for the entry cut on the rim, I am tending to start more with the flutes at maybe 1 o'clock rather than at 3. The gouge doesn't want to skate as much that way as it does if the flutes are at 3. How much it skates depends on your entry angle, which means it should be parallel to the outside of the bowl. I start inside the bowl and adjust my bevel angle till it just starts to cut. Then pull the gouge out and angle it maybe 5 degrees more so that you are aiming slightly to the outside of the bowl and very gently start the cut.

As for how sharp, the discussions still go on and on. Sharper/higher grit = cleaner cut. Coarser grit = cleaner cut. More teeth = going dull faster. Fewer teeth = going dull faster. John Lucas did a test with some ebony and couldn't really see much difference between the cuts. That may have been the wood, but I don't have much experience with turning ebony. I had some punky big leaf maple that I was turning once, and there was considerable tear out. I took a gouge that was sharpened on a 1000 grit CBN wheel, and that cleaned up almost all of the tear out. I am guessing that most of the time, the 180 grit is all you need, but some times the finer edge does have an advantage. As near as I can tell, a 1000 grit ground bowl gouge seems to go dull faster than a 180 grit gouge. I did try a skew, and yes, I do use them some times, on some green big leaf maple that had some nice curl in it. I sharpened up to 8000 grit on stones, then stropped on 800, then 8000, then 15000 grit pastes, and made some cuts. The peeling cuts still left some tear out, and my other cuts did seem to leave a much cleaner surface, even with my limited experience on the skew. I don't have any dry big leaf maple to try this with.

I have never understood the idea that a smaller gouge will leave a cleaner surface than a bigger one. Just seems to me it is like Yogi Berra said, "it is 90% mental and 10% in your head". I have tried it some and can't see or feel any difference. It could just be me.

robo hippy

 

[William Rogers]

I sharpen to 180 CBN grit. I use my gouges right off the grinder, except for the final cut I do a quick hone with a leather strop. I use mostly M42 and V10 tools. When a gouge is dull it is dull regardless of the steel, so I see no need to use M2 gouges when better steel is available.

 

[Randy Heinemann]

@odie Coming from the world of flatwork where I sharpen my chisels and plane blades to 16,000 grit on a ceramic 'stone', only sharpening turning tools to 180 grit or 600 grit doesn't seem nearly sharp enough.
Not wanting to open the proverbial can o' worms but is it because when turning a keener edge needs to be sharpened more frequently?

It may not sound like it but that really is what most sharpening adivce says. I have gone contrary to that by equipping my Tormek with a 600 grit diamond wheel (so I can also sharpen carbide inserts) and it does a great job, but I have sharpened at in-person class sites with much coarser wheels and I don't seen any real difference in cut quality or how long a single shaprening lasts. The case can even be made that using a coarser wheel might yield a longer lasting sharpening since the edge isn't as brittle.

 

[Odie]

@John Hicks .....

Hi, just thought I'd mention that my post #11 was not directed at you, although it was directed at a few other turners.....some whom are known on these forums.

If you study the works of other turners, it's easy to see, and conclude that the great majority of turners (well known and not so well known) choose lathe turned shapes that are much more compatible with power sanding. It is power sanding that alters the geometric integrity of a cross grain oriented bowl....that's just the nature of aggressive sanding when it's applied to alternating long grain and end grain. The end grain is more resistant to power sanding than the long grain, and because of that, there is nothing that can prevent the abrasive from taking more from the long grain, than it does from the end grain.....resulting in a loss of geometric integrity. When that geometric integrity is less than perfect, it's impossible to get multiple finely executed lathe turned details that look right to the eye.....because they rely on perfect geometry to have great aesthetic appeal.

A finely executed gouge cut that is without tearout, is what allows one to eliminate the need for power sanding. Hand honing is one element that allows that kind of a finely executed cut to take place. (I must mention here, that it takes much more than a finely honed edge to get a tearout free cut, but it is a necessary element in the total equation.)

The goal should be to start sanding with the finer grits, such as 180 and 240. If you can do that, it opens up a whole new set of possibilities that are not possible when aggressive power sanding is necessary.

-----odie-----

 

[Odie]

Try turning with a chisel honed to 16000 grit keenness, you lose the edge in mere seconds

You know, Brian......there are times when I prepare a turning tool, and it takes only a few seconds before I'm done with it!.....but, I get your point here. The keen edge is gone very quickly. Quite often, I am done with a scraper intended for a shear cut......before the grinder wheels stop turning. ....It's usually a different story with gouges, because gouges get re-honed several times before they are returned to the grinder.

-----odie-----