Bowl bottom problems & ???'s

[Don C Davis]

I recently turned several smallish bowls for my Mom, and I had a lot of issues with getting the inside bottom of the bowls flat--I don't know if I'm just retarded, but I haven't had this issue on the normal (larger) bowls I turned. What appears is I have a raised section in the exact center and then a dip at the outer edge of the bottom of the bowls. This is not really obvious until I start to finish--but it's there without much question when I get done.

Just wondering if you folks have any advice for methodology to insure you have a nice flat bottom on your turned bowls?
Thanks for any advice/input!

 

[Mark Wollschlager]

I used to spend a lot of time trying to get the bottoms of my first bowls flat.
The center was always dipped or raised a bit.
I used a square scraper to get it close.
The rotation speed from the outside to the center is different and you don't dare go past the center with the tool.
Then I started turning bowls with rounded bottoms, never really looked back.
It is far easier to get the curve of the bowl and concentrate on the wall thickness than getting the bottom flat.
With practice.

 

[Richard Coers]

Not retarded, just inexperienced. Or even you've never been shown how to do it easily. I rarely make a flat bottom bowl, but even on the bowls I do turn, I will use a large shallow radius scraper on just the bottom. I start below the center and drop the handle to cut out the dimple. Then sweep to the side. Kind of a two stroke method. I assume you are not power sanding? It's much easier to flatten a bottom with power sanding. Larger discs are better. Also get a stronger light if you can't see the problems in the bottom before finishing.

 

[Owen Lowe]

This is a problem when you can’t align the tool rest parallel to the bottom to use as a guide (because the bowl may be too deep for the tools at hand). The larger the bottom surface the more challenging it becomes.

Try using a straight edge to see the dips and hills. I use whatever straight edge spans the portion I’m concerned about to determine consistency. For small bowls, both long and short dimensions of credit cards (or sharpening cards) are handy; for larger bowls I use a 6” rule. I don’t super-mind a small dip toward the center but any kind of hill just irritates me!

 

[hockenbery]

I would suggest trying Richard’s method.

What I do to check the interior of the bowl is without looking slide my hand from the rim to the center.
By not looking i’m Forcing my sense of touch to the top sense.

I will feel any bumps. I usually correct them with gouge.
Many turners will often follow the bump with the cut and not remove it.

What I do is think of leveling a small hill I want to cut a line from hill start to hill end. Tiny cut to start, getting deep, then tiny as I exit. With practice you can do this with a gouge.

One issue with flat bottoms is cutting straight into endgrain which is hard.
I try to have some curve going into the bottom center.
Makes the cut easier and it is more appealing to me.

 

[robo hippy]

Well, this one is a bit dated, and a new one, maybe before the end of the year will be specifically about turning the inside of the bowl:

View: https://www.youtube.com/watch?v=QlEfNb9A1Ac


Sweeping a scraper back and forth, very lightly can leave a fairly good surface, but not the best. A negative rake scraper does about the same job. I prefer a shear scrape (one video dedicated to that). Other than that, learning to move with your body rather than trying to use just your arms. Oh, your left hand does nothing other than rest on the tool shaft. Right/handle hand does all the steering, and learning to steer in a straight line or smooth shallow curve, takes some practice.

robo hippy

 

[Bill Boehme]

Almost nobody can get a perfectly flat bottom whether on a bowl or a platter. Even after you are certain that it is flat and put a finish on the wood ... there they are ... those dreaded ripples ... just like tossing a pebble in a pond. That's one of the reasons that woodturners prefer a bottom with a gentle curve that smoothly flows right up the side to the rim. There are some other advantages to a curved bottom such as being more stable and less likely to crack. A curved bottom bowl is also easier to clean. And, like the bowls that potters make, smooth flowing curves are usually more aesthetically pleasing. Once I discovered curved bottoms, like Mark, I never looked back.

 

[Mark Jundanian]

Well, this one is a bit dated,

Very nice video. Good demonstration and good quality video.

I volunteered for the video committee of our local chapter, so I'm curious. How are you accomplishing the camera work? It seems you are working with an experieced videographer .

I will throw in this 2 cents on flattening a small hump, don't underestimate the efficacy of a sanding block.

 

[robo hippy]

My camera man and I have been working together for at least 5 years, can't remember exactly,... In the latest one about 'Scary Scrapers' he is filming and asks, 'Am I standing out of the line of fire?', and we had to leave that in. I figure my time is better spent working on stuff and letting a professional handle all the editing and splicing. One change from when this one was done is that we use the camera mike and/or one on a tripod. You can hear the volume change every time I turn my head. The clip over the ear type work, but the clip on the lapel type don't, unless you keep your head and mouth in the same spot.... Negative rake scrapers and standard scrapers do a fair job, and the 80 grit gouge on a firm pad does a fair job, but some times the 80 grit scratches are deeper than the tool marks... 80, 100, 120, 150..... I don't skip grits. Medium pad at 220 or 320.

robo hippy

 

[Owen Lowe]

TOOT TOOT! <my own horn>

Guys, Don said he didn’t see the bottom ripples/dips until he put finish on the bowls. It’s not like his technique is lacking as he hasn’t had an issue with larger bowls just these small ones. Curve inconsistencies are much more obvious to the eye after a finish is put on than any examination with a hand can detect.

After you have gotten through with your last tool how do you determine that the inside curve flows consistently?

 

[Ronald Plumley]

Not retarded, just inexperienced. Or even you've never been shown how to do it easily. I rarely make a flat bottom bowl, but even on the bowls I do turn, I will use a large shallow radius scraper on just the bottom. I start below the center and drop the handle to cut out the dimple. Then sweep to the side. Kind of a two stroke method. I assume you are not power sanding? It's much easier to flatten a bottom with power sanding. Larger discs are better. Also get a stronger light if you can't see the problems in the bottom before finishing.

I second this... Power Sanding is a huge time saver and frustration reliever.

R

 

[Don C Davis]

Hey folks, I genuinely appreciate the feedback--and to the point, Owen Lowe is spot on, I haven't had this issue on larger bowls. Very interesting about a curved bottom being more stable than a flat one, I absolutely wasn't aware of that, so I may consider just going to curved bottoms--also interesting, I didn't power sand these particular bowls, on some of my larger bowls I have and I haven't--just haven't had this issue before--I may try my vacuum chuck out and see if I can't turn the bottom of these with a curve, I obviously could power sand them--may just have to try that!!!
Thanks folks again

 

[Don C Davis]

Reed, I just watched your video, good instruction there bro!! Thanks for sharing

 

[Breck Whitworth]

I will add my two cents concerning the dimple or mound in the bottom of a bowl. removing or fixing the problem is much easier (regardless of technique you use) if you see it early, my advice based on what I learned is to use better light. I changed to powerful LED sunlight bulbs. I missed seeing most of the ones that occurred in my work. Now I can see almost immediately if I need to make another few passes with the finish gouge. It may not be an issue for you but it helped me.

 

[Don C Davis]

Breck, I have a flexible neck light that is pretty bright that I turned inward to look at these bowls as I was turning 'em, but maybe I should try a brighter one. I really think trying a curved bottom may be my best approach---Robo's vid gave me some ideas too!
Thanks for the input brother!

 

[Bill Boehme]

Concerning Breck's comment about LED lighting, I bought a really bright LED light at Rockler's. It is rated to have a brightness of 4400 lumens. The brand is Keystone. There are two sizes. I ought the larger one. I was so impressed that I bought two more. One is dedicated to photographing woodturnings and the other two are in the shop. HERE is a link.

 

[robo hippy]

Brightness in lighting is one thing, the other is spectrum. I think the LED's are catching up to the florescent bulbs now. Mostly you want as close to natural sun light as possible as that is what we have evolved to see in. The therapy lights are good for those of us in grey cloudy country.

Now, don't get me started on a good bottom should curve......

robo hippy

 

[Richard Coers]

If you are trying to judge a fair curve or flat surface, a light shining directly on it helps, but may not be the best. You want the light in front of the surface and you looking at a reflection of the light.

 

[Randy Heinemann]

Well, this one is a bit dated, and a new one, maybe before the end of the year will be specifically about turning the inside of the bowl:

View: https://www.youtube.com/watch?v=QlEfNb9A1Ac


Sweeping a scraper back and forth, very lightly can leave a fairly good surface, but not the best. A negative rake scraper does about the same job. I prefer a shear scrape (one video dedicated to that). Other than that, learning to move with your body rather than trying to use just your arms. Oh, your left hand does nothing other than rest on the tool shaft. Right/handle hand does all the steering, and learning to steer in a straight line or smooth shallow curve, takes some practice.

robo hippy

Your videos and answers on forums are always so helpful and informative. This particular video was extremely helpful to me. Partly I'm just not that experienced and have found various methods to get essentially flat bottoms with the tools I have. This video gave me some other techniques to try and, above all, practice (which I don't do enough of).

Finally, one of the reasons your videos are so useful is that you help me understand that my problems in turning are not that unique and that, they tend to become less of a problem over time.