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Bowl inside sanding

Kent Reisdorph said:
the rim to center method as described by Kent Weakly at www.turnawoodbowl.com. He recommends leaving the center mass for stability
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Ross Berning said:
I saw that video and not sure if the physics make sense. More mass is more inertia,…
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I’ve always considered the effect was due to the physical thickness, not the mass.

But regardless of the theory/reason it does help. I personally use the rim to bottom method. When thinned to the bottom, I use the “left hand support” method on the outside to control flexing if needed. That works too.

JKJ
 
hockenbery said:
True but it is the indirect support that you benefit from.
What mass in the bottom of a bowl or hollowform does is strengthen the hold of the faceplate or chuck.
This mass decreases vibration significantly.
Also stair stepping leaves thicker walks close to where you are cutting the final thickness.

Creating a thin wall near the chuck or faceplate mount lets the work flex around the mount.

You can get other vibration cutting walls from things like bevel drag and too much bevel pressure.

In this clip from a demo of returning a dried 11” sycamore bowl I’m doing the finish cut on the top of the side wall.
The ring in the bottom is from the friction drive of the bare chuck jaws. I’v turned te walls down toward the bottom but have not yet turned the bottom. You can see a few stair steps.
View attachment 67392
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What you say makes complete sense, in the video in question he leaves a big cone in the middle and makes the claim about it helping. Think a W shaped cross section, to a degree.
 
Odie said:
You may not be able to completely eliminate vibration, and there are two types.....static vibration, and that vibration which is caused by the interaction of your tool to wood.
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You didn't define static vibration, but I am guessing that would be the vibration when the tool is not in contact with the wood
 
Bill Boehme said:
You didn't define static vibration, but I am guessing that would be the vibration when the tool is not in contact with the wood
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Yes, you are correct, Bill.

Thanks for the clarification.

=o=
 
You can make a spindle washer from a plastic laundry soap bottle. I use the big orange ones from Costco. They work great and cost nothing.
 
All my Nova chucks except the Titan have inserts which I’ve got a dedicated wrench to remove them with. For the Titan, I made this wrench with a piece of an Allen wrench glued into an oak handle. It’s shaped exactly to the chuck body and has a piece of inner tube to help with padding and friction. Works great.IMG_6531.jpegIMG_6533.jpeg
 

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Lou Jacobs said:
All my Nova chucks except the Titan have inserts which I’ve got a dedicated wrench to remove them with. For the Titan, I made this wrench with a piece of an Allen wrench glued into an oak handle. It’s shaped exactly to the chuck body and has a piece of inner tube to help with padding and friction. Works great.View attachment 67611View attachment 67613
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I will happily steal this idea. Genius level
 
robo hippy said:
Oh, the joys of turning soft maple! There is a lot of big leaf maple here, and one reason I don't like it is because it is prone to tear out, no matter how sharp your tools are. I have never taken a gouge to the levels that I take my hand planes to though.... For sure, I ALWAYS finish with a shear scrape, and have one video dedicated to that. As for NRSs, they do a good job when sweeping across the bottom. However, when going up the sides of a bowl, they are still scrapers, and you have unsupported fiber, so there is still going to be some tear out. Time for the 80 grit gouge. As always, a fresh gouge for the final finish cuts is necessary. For a long time, I figured that a smaller gouge would not be any advantage. But, as some one who has to experiment. I tried a 1/2 inch gouge, exact same geometry as my 5/8, and I did seem to have an easier time making smoother cuts on the inside of the bowl. It didn't seem to make any difference on the outside of the bowl. This may be because on the inside of the bowl, you have 3 areas to cut. One is the side wall which is similar to the outside of the bowl, two is the transition, and three is the bottom of the bowl. Slightly different grain orientations for all 3.

robo hippy
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Thank you for acknowledging the difficulty of working with big leaf maple! I was going nuts thinking I was doing something wrong (I tried everything including NRS), but it's reassuring that someone as experienced as you has had problems with it too!
 
If it was practical, I would take one of my gouges to a level of sharpness that my bench planes and chisels are and see if that made much difference.... I did use a 1000 grit CBN wheel once on some punky BLM, and it made a big difference.

robo hippy
 
One trick I use is to minimize tearout on the inside of the bowl, is to use a bit of oil finish to lubricate the wood as you cut. It's a bit like trying to shave with and without shaving cream.
 
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As I do mainly hollow forms, I have resorted to using the inertia sanders as the best way to achieve a good finish. OK the centre at the bottom of the HF can be a challenge, but it can be done.
 
Odie said:
Getting a continuous finely tooled curve on the interior of bowls......one that needs no leveling and a minimum of sanding is one of the more challenging aspects of bowl turning.

I turn Big Leaf Maple bowls often, and this can be done with great success.

In my opinion, one of the best single bits of advice you've gotten.....is to use a negative rake scraper. They take some time to develop skills to the point where you have the minimum amount of work left to do when you transition from tools to sanding.

Sharp tools can't be stressed enough, and I probably turned for twenty years before I really knew what sharp was......and, how to consistently maintain that kind of an ultra-sharp edge.

Another thing that will affect the outcome of a very refined tooled surface, is to find the right rpm......one that minimizes the vibration initiated by the edge cutting wood and the static balance. A Oneway bowl steady is a great invention.....I use one on nearly every bowl I make. It helps dampen the vibration, and anything you can do to minimize the vibration is to your advantage.....it will definitely affect the quality of the tooled surface you are capable of. You may not be able to completely eliminate vibration, and there are two types.....static vibration, and that vibration which is caused by the interaction of your tool to wood. The best rpm tends to help with the static vibration a bit more, and the Oneway bowl steady tends to help more with the vibration that initiates from the interaction of tool cutting wood......however, it is a combination of all the elements of the total equation working in concert with one another that gives that final boost of capability.

Refined tool skills cannot be taught......they can only be experienced through observation and adjustments. Some turners may learn faster than others, but everyone needs to gain an understanding of all the things that affect the quality outcome of a sharp tool cutting wood.....it is multi-faceted.

=o=
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Are you using your bowl steady just on large bowls, or on all sizes of bowls? Are you sharpening your gouge to the point of honing? e.g. using a 1000 grit CBN wheel and honing after it is finished? I'm having a heck of time getting rid of tear outs on Big Leaf Maple.
 
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Big leaf maple loves to tear out, no matter how sharp your tools are. I have to start with 80 grit on it. I have yet to take a gouge to the level that my bench chisels and plane irons are.... Maybe some day. I don't turn it often because of this.

robo hippy
 
Craig Barton said:
Can you describe your sharpening technique for Big Leaf Maple? Do you use a high grit wheel (e.g. 1000 grit CBN)? Do you hone after sharpening on the wheel?
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I can't speak to Big Leaf Maple, but I can point you to threads on CBN grits. There are some posts here from about a year ago where someone (Al Hockeberry maybe) posted results of sharpening on an 80 grit wheel vs. a higher grit. The results indicated that the high grits didn't provide a noticeably smoother cut. I'm summarizing so you'll want to check it out. Use forum search to find that thread. FWIW, my two CBNs are 80 and 360 grit.
 
Kent Reisdorph said:
I can't speak to Big Leaf Maple, but I can point you to threads on CBN grits. There are some posts here from about a year ago where someone (Al Hockeberry maybe) posted results of sharpening on an 80 grit wheel vs. a higher grit. ……..Use forum search to find that thread. FWIW, my two CBNs are 80 and 360 grit.
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@Craig Barton

I didn’t do the comparison post. My wheels are CBN 80 and 180. I sharpen my 1/2 bowl gouges (5/8 bar d) on the 80.
Everything else except skews on the 180. Skews I sharpen on a tormek and hone with the tormek strop wheel

I have rarely turned big leaf maple
I don’t recall ever having tear-out issues.

This is a piece about 12” highIMG_2424.jpeg
I wasn’t real happy with the transition to rim element but it sold quickly
 
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I sharpen on 180 and 600 grit wheels for my gouges. If I wanted to really sharpen my gouges for BLM, I would polish the flute with fine grit, like 1000 or 2000 grit abrasives, grind on a 1000 grit wheel, then strop on my Tormek. I have not done that one yet. I always get tear out on BLM, more than just about any other wood I turn, except for a bond dry piece of Koa that some one gave me. I had to dampen the inside down about 3 times to get a clean enough surface so I could sand. I have never turned any fresh Koa. Some woods just cut better than others. Madrone is one that cuts better, very similar to pear or dog wood.

robo hippy
 
Michael Anderson said:
I’ve only used the “board between the jaws” method a couple of times. It’s effective though, but like you often I’m removing the chuck with the piece still intact (ex. to get an upright view of the piece).
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I'm going to start doing this. My brain goes, "looks great" on the lathe. Then I stand it up and it looks completely different. My brain just can't "see" the whole picture when the piece is on the lathe.
 
Work on NRS skills to clean up tool marks and tear out like you showed. Sometimes the cutting edge needs to be at a bit of a shear angle, just depends.

Spot sanding with the lathe off to clean up what the nrs doesnt get. Do all power sanding at low lathe rpm, 100-250rpm, and low drill rpm 200-300. Hand sand at lower rpm, depends on dia. Heat is the enemy.

Wall flexing vibration - thinner bevels create less drag for gouges, reducing force. Smaller tool presents less drag, 3/8” bs 5/8” gouge. I use an 1/8” thick piece of leather held in the front hand, held on the OD of the piece. Gouges and nrs as needed. At times I use a bowl steady, cheap one like this:

 
Ross Berning said:
After roughing dozens of bowls I’m working on finishing cut skills. Feeling better about my progress on outside finish quality than interiors. I’ve got this soft maple piece on the lathe with what seems like tear out. With both hand and power sanding this area is 98% as smooth as the surrounding area but it isn’t really getting smaller. I’ve spot power sanded with 120grit. Other tool marks came out fairly easy. Is this a just keep sanding situation or would some sanding sealer or other technique help? I have not sanded in reverse as the chuck grub screws have gone missing.

I appreciate your wisdom here!
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if you lathe is not against a wall instead of sanding in reverse you could just stand on the other side of the lathe and sand from that side it accomplishes the same thing.
 
robo hippy said:
I did have a "Delrin" washer for my chucks and lathes some years back. There was no noticeable run out in the chuck or the bowls, probably because the washer was machined flat. Delrin is capable of that. It eventually got lost in the shavings and I never replaced it.

I may have to redo my thinking on NRSs. I am still of the opinion that they are still scrapers, and you will still end up with some tear out in unsupported grain, which is the side grain in bowls. Maybe I do need to sharpen more frequently. One good thing about them is that as you ease them into what ever it is that you are turning, they nibble off the high spots so you get a more true surface....

robo hippy
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I have a 1 1/4" negative rake scraper works wonderful. Sharpen frequently. You can often just sharpen the bottom side and not have to touch up the top and when you do grind the top side do it first. I sharpen the bottom part when I can no longer feel the burr which doesn't take long to lose probably way less than a minute and the burr is gone. A light touch up for the bottom edge and the burr is restored.
 
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