The inside of the bowl

[Reed Gray]

After replying to the thread about the heavy duty scrapers, I got to thinking about one of the things in turning that drives me crazy, and I don't seem to be able to fix with any consistancy. I can never get as good of a finish cut on the inside of a bowl as I can on the outside. I can get a finish cut on the outside that needs only minimal sanding, but the inside...... In theory, I should be able to do this. I have turned several thousand bowls, and I have reached a plateau. I can get a smooth surface most of the time that doesn't require 80 grit, and little or no tearout, but the concentric rings, and smaller bumps and ridges still appear. Some times I get almost none, but most of the time there are some. I do grind off the sharp edge of the bottom of the gouge after I grind it, I use my right hand to do all the pushing, and the left hand barely guides the gouge (thanks to Soren Berger for that tip), and I can use my left hand to steady the outside so I can start at the top and make one final pass from rim to bottom, but getting the inside as good as the outside seems to be harder than learning to use the McNaughton coring system. Can anyone help me?????
robo hippy

[Pete Jordan]

Stu has a video on youtube that shows him using a Eli Aversari tool that looked interesting. I have ordered it from Highland but they said it will take a couple of months to get here since they don't stock it.

[Dean Thomas]

I do grind off the sharp edge of the bottom of the gouge after I grind it...
Dear Robo Hippy, (I feel a little like Ann Landers with that name!)

Hey Reed, when you say you're grinding off the sharp edge, I'm confused. :confused: Are you talking about the wire-edge burr that's caused by the grinding process? That's usually found on the TOP edge of the grinder.
________
_______/
---or---
________
_______(
to allow for those who use smaller grinding wheels. :)


That's the basic shape of a ground scraper, yes? Except for the downward angle caused by lifting the handle, this is how the tool addresses the wood and on the top face of a tool that's ground or "properly" burnished, there's gonna be a wire-edge burr. Most of the time, it's that burr that actually does the cutting. Not all, but most. Some woods do cut better (and slower in my experience) without the burr, but MOSTLY it's the burr that does the work. Removing that is not always a good thing.

Second, if you really DO have a burr on the bottom, you don't really need to remove it anyhow since you never rub or glide the bevel with a scraper.

Can you provide some more explanation? Maybe what kind of sharpening system you're using and maybe type of wood and how you're using the tool?

[Paul Heely]

I think what Robbo Hippy is doing is shown in the picture below, this is what I understood. I do the same thing so that as the gouge transitions from side to bottom during the cut it is less likely to bruise the wood if (when) that area comes in contact with the wood. While not necessarily sharp the area in question does form an edge of sorts that can damage the wood.

[Reed Gray]

Like Paul said, I grind off the heel of the sharpened edge. This is supposed to help get rid of those concentric rings that I see in the bottom of my bowls, and does a lot to prevent the burising that I used to find and couldn't explain. It isn't the sharpening, there has to be some sort of trick of tecnioque that I am missing.
robo hippy

[Dean Thomas]

I'll leave my comments as a record, but have to back up a bit after taking time to reread the initial post. I think I got a couple of posts crossed in my food deprived brain, dealing with gouges as opposed to scrapers inside bowls. Sigh. A mind is a terrible thing to lose.

Again, I understand doing that for a GOUGE, but not a scraper. It's not unusual to relieve a bowl gouge's bevel, even a couple of times to create a triple bevel tool.

Did I miss something, Reed? Do you also relieve the bottom of the scraper's bevel THAT NEVER TOUCHES WOOD ANYHOW???? If so, why so??

Caps for emphasis only.

[Dick Strauss]

Reed,
As you probably know, the angle of the grind is everything for getting around the corner. My buddy sharpens his gouge to about a 45 degree angle. I sharpen mine to a 60 degree and 70 degree angles for my 5/8" and 1/2" gouges respectively. I'm measuring the angle from the axis running the length of the tool not knowing what the standard reference is. In other words, my gouge nose has less of a point than my buddy's (some may say mine has a 30* angle if measured from vertical rather than horizontal). My buddy can't get around the corner and do the bottom as well but has a slightly easier time with the rim. I like my compromise better but do have to lean over the lathe when I start the cut into the rim. If you have the problem with the pass down from the rim to the shoulder, give your tools a steeper profile.

Some folks round the heel like you do. Others create a secondary bevel to chop off the heel. Both methods allow for a tighter turn radius in the shoulder area of the inside by presenting a shorter floating bevel to the wood. However, the secondary bevel method is more effective for decreasing the contact area.

Another thing that helps the curve in the shoulder area is to turn the nose of the gouge slightly uphill just as you start to turn the corner. This effectively shortens the length of the gouge bevel that is in contact with wood and allows for a tighter curve to be cut if needed. Rotating the tool counter-clockwise starts to align the curve of the steel with the curve of the wood allowing for a smaller arc. Then you keep the nose upward until just before you reach center. This angle never goes beyond about 1:30 position if you were looking at a clock (as you face the headstock) and is changed progressively as you turn. In other words you increase the approach angle between the shoulder and middle (from 3:00 to 1:30), and decrease the angle (from 1:30 to 3:00) from the middle to the center of the piece.

I hope this helps to answer your question or gives you another option for future success! If not, I'll try to explain it in English this time.

Good luck,
Dick

[Brodie Brickey]

Reed,

I think Dick may be onto something. I have the Mike Mahoney video "tree to table" (or something like that). Mike uses a bowl gouge for the finishing pass inside that is very close to vertical, probably 70-80 degrees.

I got one of those and it does allow me to make the turn. Admittedly, if you were doing a tall tulip shape, you might have problems with the transition, but for gently sloped bowls it works great.

Here is a pic of the kind of grind I'm talking about. http://www.woodcraft.com/images/family/web3728.jpg

(I don't have the drawing talent like some so here's a stolen picture.):)

As you can see from the extreme angle, its useless outside, but once inside you can ride it around the transition and hit the bottom still running.

Hope this helps.

[Reed Gray]

I did relieve the bottoms of my scrapers once, and that has all been ground away. The purpose was to cut down on sharpening time and pressure. I may do it again, but it doesn't really have any benefits.

Going through the transition is always interesting. The transition to me is the area between the side of the bowl, and the bottom. On flatter bowls and dishes, it is easy. On deeper bowls, it is harder. I actually have a deep bowl gouge that has about an 80 degree bevel. I can take the swept back grind (I guess that it is about 45 degrees, but I never measure, just standard Ellsworth grind) down through the transition and use the bottom of the bowl gouge for going across the bottom. Since the angle is so blunt, the handle comes out of the bowl almost at 90 degrees to where you are cutting. On bigger bowls and deeper bowls this is almost impossible with a swept back grind, because you run into the tool rest, and the side of the bowl. This is more of a problem with a gouge that is getting short. Some times after making the entry cut, when I get towards the transition are, I will roll the gouge more onto its side for going across the bottom. This helps some what. I have also tried the secondary bevel, and it works to a degree.

All this being said, for some reason my finish cuts are never as nice and clean as those on the outside of the bowl. I just keep thinking that there is some great cosmic secret to turning the inside of the bowl that I haven't discovered yet. I have long thought that it was because you can't get as good of a look at it as you can when you cut the outside. I think it should be some kind of a touchy/feely thing that you do as you cut, but that seems to evade me also. I guess it is kind of like finding a word that rhymes with orange. There is supposed to be one, but we aren't ready for it yet.
robo hippy

[Ken Fitzgerald]

All this being said, for some reason my finish cuts are never as nice and clean as those on the outside of the bowl. I just keep thinking that there is some great cosmic secret to turning the inside of the bowl that I haven't discovered yet. I have long thought that it was because you can't get as good of a look at it as you can when you cut the outside. I think it should be some kind of a touchy/feely thing that you do as you cut, but that seems to evade me also. I guess it is kind of like finding a word that rhymes with orange. There is supposed to be one, but we aren't ready for it yet.
robo hippy


Reed,

If you really get desperate....try rolling some chicken bones, feathers and a little hair from a gnat.....all the while mumbling......you have to do it on the bed of the lathe!:eek: :rolleyes: :eek:

[Dick Strauss]

Brodie,
My 60* 5/8" gouge is the main one I use on both the inside and outside. It works equally well either way. I didn't get this from watching any videos but just discovered it while experimenting.

Reed,
All my measurements were in reference to the nose angle of a bowl gouge, not the swept back wing angles. All of my comments were solely about bowl gouges. The 60* angle has the added benefit you mention in that it doesn't get in the way as you make the transition from the wall to the bottom in a deep bowl.

Another reason for issues might be the whole uphill vs downhill wood grain situation. If you turn the foot on the outside of the bowl from the foot out, you are always cutting downhill with respect to the wood fiber direction. As you cut across the bottom of the bowl you start cutting uphill into the grain and you'll experience much more tearout.

Do you rotate the tool during the transition like I mentioned? This is another idea I discovered as well.

[Paul Engle]

I got you were talking about little bumps on the inside, if you use the left side wing down , gouge horizontial so the wing is cutting in the middle of it with the right side about 1/8 of an in from the surface and gently start at the bottom and work your way out side now , with the handle down about 30 degrees from horizontal ( donot axial turn the gouge leave the flute facing the side wall ) or so ( Ellsworth recommends 45degres) , you will find less bounce and a smoother feel to the gouge, this is the finess part of bowl turning that allows the gouge to cut more often. In machining the rule of thumb is higher speed - slower feed gives smoother finish.Now try speeding up your machine to the next higher setting, Of course you will have to practice to get a comfortable feel , try it on a practice piece on the outside first to get confident then try on the inside, you may find you have to roll up closer the nose to get 45 degrees but you will be cutting tangent to the grain and that is what you want and on the inside , you have less room to manauver. If you practice to find the sweet spot on some scrap first then approach the " good " one and you will be more relaxed. If you cut parallel with the grain you get bumps and tear out , way more so than if you cut across it like the Berger tool does , it cuts across the grain by virtue of the angle of the cutting edge. Hope this helps. On my scraper I ground a slight negitive rake on the top and no more catches , it is very stable and for giving but I do have to sharpen somewhat more often. I have learned to use the wing on the bg and hardly ever us scraper any more except for hf ' s to clean up the inside of a bowl.

[Bernie Weishapl]

I do the same as Brodie explained. I got to see Mike do his thing on the final pass with his bowl gouge. He suggested the P & N traditional grind bowl gouge. I got the 3/8" and 1/2". I keep them sharp and use them for the last pass and it follows the contour of a bowl very well and leaves a very smooth finish. If not I spritz with water or rub oil on the tear out and make another pass. That usually takes care of it. I have never had very good luck using a scraper inside of a bowl for some reason.