tools/techniques for shaping the rim of a bowl or platter

[Joe Aliperti]

I'm a fairly inexperienced turner, and twice have had catastrophic failures while attempting to fine-tune the rim of a bowl. Both times, I was using a square-tipped scraper with a very light touch. One time the glue block failed, and another time the bowl exploded into several pieces.

Please share some tips on tools, techniques, or lathe speed, so I'm not afraid to shape the rims of my bowls.

[Ken Fitzgerald]

Joe,

I use a bowl gouge.

[Steve Schlumpf]

Joe, I agree with Ken! Use a sharp bowl gouge to slice the wood and not only will you shape the rim but you will minimize the amount of sanding you have to do later.

Lots of folks like to use scrapers on bowls but most of the time it is on the inside to clean up bowl gouge marks. Using a scraper on the rim is to easy to get a catch - IMHO - especially when you are first learning because the angle of the scrape is most important. Get the angle correct and you get a great finish - wrong angle and it digs in and you get a chance for a design modification!

[Wally Dickerman]

In reading your post it sounds like you are trying to use a scraper on the rim after the walls are already turned thin. Can't be done without problems as you've discovered. The wood has little support and will vibrate. The rim should be completed before doing the final hollowing.

If you've done a good job when gluing the glue block to the wood it won't come off when turning. It's a glue joint, so the surface of the glue block and the bowl bottom must be true and flat as in any other glue joint. I've found that when separation occurs, it's usually because not enough glue was used. A good glue joint is stronger than the wood itself. (Don't use plywood or MDF for a glue block...not enough strength)

Wally

[David Christopher]

Joe, youve allready got some good advice..the only thing that I would add is get some cheap wood and practice....if you care to look at this thread you can see that I was practiceing the same just a few weeks ago....good luck

http://www.sawmillcreek.org/showthread.php?t=113461

[Joe Aliperti]

Thanks for the advice everyone.

I think Wally hit the nail on the head. With the walls turned thin, even a light touch with the scraper will cause vibration, which leads to a catch. I assume the same thing may happen with a bowl gouge if I'm making a shearing cut instead of riding the bevel.

I've had the tendency to use a bowl gouge to do the majority of the work, and then use scrapers to fine-tune the shape and remove tool marks, but perhaps it is best to do all of the fine detail on the rim prior to bringing the wall down to final thickness.

[Reed Gray]

As a big fan of scrapers, which is considered odd to some, I agree with Wally about your problem. If you use scrapers on the outside of a bowl, you will notice there is no vibration or chattering. There is a lot of mass on the inside of the bowl yet, so everything is pretty solid. When you remove the inside, then the walls are thin and will vibrate when tools are applied, both gouges and scrapers. When I am using a scraper for a finish cut on both inside and outside of a bowl, it is at a shear (45 degree angle) rather than flat on the tool rest. Flat on the tool rest is a scraping cut and is a great roughing cut but a lousy finish cut. It tends to pull the fibers more than slice them, which puts more pressure on the wood. Ever get that howling/screeching sound with a scraper on the inside of a bowl? You will see evenly spaced chatter marks on the rim. The noise and chattering if from a scraping cut. You can do the same thing with a gouge.

It is best to turn the inside down in stages to finish thickness, much more so on larger bowls (anything over about 8 inches max) than on small ones (6 inch and less). Finish turn about an inch or maybe 2, then go down another inch or 2 till you hit the transition area (wall of the bowl to the bottom). Blend in the steps as you go. Any wood, no matter how dry will 'adjust' as mass is removed from the center, and because the cuts go through both end grain and side grain as you cut, and the grains cut differently,there will be some excentricity to the turning. You can use your hand as a steady rest on the outside of the bowl. Note: round over the rim of the bowl first as that edge is sharp, and apply only gentle pressure to the bowl. If your hand is getting hot, then you are pressing too hard. Also, your hand pressure should be the same amount of pressure that the tool is presenting to the wood. Too much pressure is as bad as none at all with a scraping cut.

robo hippy

[Bernie Weishapl]

Joe I don't use scrapers at all. I use a bowl gouge from start to finish. One DVD I would recommend is Bill Grumbines Turned Bowls Made Easy. He shows you cut in there that will smooth your bowls easily. Also Mike Mahoney's From the Tree to the Table is a great DVD. He also shows different cuts with a bowl gouge. He uses a conventional grind which P & N has. I started using these for my last cuts and start sanding at 120 to 150 grit. I have never had good luck using a scraper.

[Steve Harder]

Joe - as a turner who has had an occasional catch with a bowl gouge when I've been trying to clean up a turning I now really like the Ci0 round carbide insert for that work. I've been getting turnings with no tool marks and I've been having fun doing them instead of stressing about the next inevitable catch. FWIW.

[Cody Colston]

Wally told you right...imagine that! :D

...and from Bill Grumbine..."first define the rim of your bowl and then you can refine it."

When shaping the bottom, before reverse chucking, use a parting tool to cut a line that defines the top of your bowl...you only need to go about 1/4" deep or so. Make sure that any defects like cracks, pith, etc are on the waste side of the line and will be turned away. That ensures you will have a sound edge for the rim.

When you have reverse the bowl, turn away all the waste down to the line you cut. Now you can refine the rim...slant it to the outside, the inside, leave it flat, round it, whatever you like. The rim has not started warping like it does sometimes after hollowing and it's still solidly backed up by the rest of the bowl. Even after hollowing down to an inch or so the rim will be stable if you need to touch it up a bit or change your design.

Once you begin hollowing in earnest, the rim should be left untouched with a turning tool. Power sanding will let you change the shape a bit although you may end up with uneven thickness of the rim if it has warped.

Be sure to always wear your face shield, though. Even with proper technique, wood can still come apart when spinning on a lathe. DAMHIKT