Getting bottom of bowl flat

[Jerry Lear]

I posted this question before but it didn't go through.

I have used a bottom bowl gauge, regular bowl gauge, and scrappers but always seem to end up with lumps on the inside bottom with a slight domed center.
I know I am doing something wrong but are unable to correct it. Any help or suggestions you can give, will be greatly appreciated.

Thanks,
Jerry

[Bill Howatt]

I don't know if there is a magic bullet for this common problem. I'll say that you need to practice your technique so you are doing your cuts in a smooth sweeping motion without starts and stops. Remember that the amount of wood past the tool as you approach the center is not as much as at the outer edge. Right at the center it is approaching zero so you have to concentrate a bit more in that area, even when sanding.

[Richard Coers]

It does require a good eye and practice. I use a 1 1/4" wide scraper with just a slight radius on the end. With the slight radius, it is easier for me to gage the arc I put in the wood over a full radius scraper.

[Reed Gray]

Here is an old video of mine that covers this subject:

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

Mostly it is keeping your body from twisting as you push across the bottom of the bowl, keep that gouge angle consistent. A scraper can do a fair job of sweeping across the bottom of the bowl because it is all flat grain. They don't work so well going through the transition and up the walls since they pull more than a high shear cut will do.

robo hippy

[Bernie Kopfer]

It does require a good eye and practice. I use a 1 1/4" wide scraper with just a slight radius on the end. With the slight radius, it is easier for me to gage the arc I put in the wood over a full radius scraper.
Richard is your wide scraper a 1 1/4” square end with a slight radius on the ends? I’ve used Simple Tools 1”wide carbide scraper to flatten bottoms of bowls and platters. But you are right it requires practice and concentration.

[roger wiegand]

try making some cardboard cutouts of pleasing inside curves that you can hold in the bowl to help you see inconsistencies in the profile.

[Don Stephan]

Richard Raffan has Youtube videos that address how to come up into the center, then swing out. You could cut tongue depressers to different lengths (if they truly have straight edges) as straight edges on the bowl bottom.

[Sam Force]

A round sharp scraper will usually do the job but there is always an 80 grit gouge that works really well for smoothing bottoms flat. I believe we could all admit to using such a gouge at some point in time. :eek:

[Neil Strong]

A round sharp scraper will usually do the job but there is always an 80 grit gouge that works really well for smoothing bottoms flat. I believe we could all admit to using such a gouge at some point in time. :eek:

Yes, coarse abrasives is one of many methods for removing any hump, but it will also leave deep scratches in the side grain in the bottom of the bowl, which then requires a lot of further sanding with finer grits to eliminate.

All of the other methods mentioned will also work. However, being able to see the hump at that stage of turning is the key to eliminating it. Rogers cardboard shapes would work.

I use a strong light source at centre height and observe the shadow from the toolrest at centre height in the bottom of the bowl. The lamp attached to my headstock is my only source of light when turning, so I get a good sharp shadow. May not work so well if you have your whole workshop lit up like fairyland.

Terry Scott uses hot glue gun rods and bends them to shape inside the bowl. They spring back to use again in the next bowl.

A good piece of thin spring steel will do the same job.

[Bill Howatt]

I don't do many flat-bottomed items like plates so my scraper use has always been a round-nosed one so it handles curves.
Reed's video is certainly well-worth watching to learn about addressing the hump and bump problems.

[Neil Strong]

A good piece of thin spring steel will do the same job.



Here is what I'm referring to there...
512119
For eye safety I join the ends together

512120 512121
You can use it in both shallow and deeper bowls



When you press it into a bowl or platter it helps me to see any corrugations, including checking to see if there is any divot/hump in the bottom middle.

[Richard Coers]

Richard is your wide scraper a 1 1/4” square end with a slight radius on the ends? I’ve used Simple Tools 1”wide carbide scraper to flatten bottoms of bowls and platters. But you are right it requires practice and concentration.
It's an old Sorby extra heavy duty. I bought it in a set at least 30 years ago. https://www.woodturnerscatalog.com/p/130/1651/robert-sorby-M2-HSS-Extra-Heavy-Full-Round-Scraper