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Tumbling Bowl Turning Suggestions?

J

Jim Bennett

Joined
Dec 5, 2017
Messages
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Location
Eagle, ID
I'm in the glue-up phase of making a tumbling bowl similar to the one by Peter M. Smith that I found at woodturner.org. Eventually I'll get to the point of mounting a rounded block of "cells" on my lathe and get to turning it into a bowl shape. However, I'm not sure about the "best" tool to use to shape the thing. When each cell is assembled, it has three side grain sides and three end grain sides. So, unlike the segmented bowls I've turned, I won't have 100 percent side grain to work with while shaping it. What would you folks suggest I use on this piece? I've got a couple different carbide turning tools and two round nose scrapers. Also have a bowl gouge, but since acquiring the carbide tools a few years ago my use of the bowl gouge has gone to zero, while my "fear" of destroying something with it has gone the other direction. So my preference would be to use the bowl gouge as a last resort. Neither of my scrapers are negative rake grind.

Suggestions?
 
Umm, what do you mean by a tumbling bowl? I am familiar with an 'earthquake' bowl, which has a round bottom so it will rock and roll if there is an earth quake. I do use scrapers for all of my roughing when turning bowls, but prefer a shear scrape, scraper with burnished burr at 45 or higher degree angle for finish cuts, and generally will use a gouge prior to that. Scrapers just leave a too rough surface.

robo hippy
 
Michael and Hugie - it is similar to the photo that Mike Brazeau posted, but in the form of a bowl, not a platter. This is one of those cases where "a picture is worth a thousand words" - Google "Tumbling Bowl" and you'll see several YouTube videos on them. The one by Thomas Anton Gerts is most mesmerizing to watch. No words, just his video, and the finished product is quite amazing.

Still wondering about the tool....... :)
 
Ah okay I see. So, it’s more of a 3D perspective/illusion than a specific form. Very cool examples out there!

Regarding tool, I imagine your best bet is a sharp bowl gouge for the exterior (shear scraping at the end), and then a ring/hook tool or cupped carbide cutter (like Hunter makes) for the interior. Maybe even get away with a sharp spindle gouge for roughing the interior.
 
I would think that tool usage would be quite similar to any other segmented turning. I've done a couple (sort of - basically glued-up cutting board leftovers) and just approached it same as I did any other bowl turning since most bowls will have both side & end grain cutting, no different than a segmented or tumbling bowl. Didn't have any major tear-out or other notable issues that I could really see.
 
I do side grain glue-ups all of the time like Brian Gustin comments. Just like turning from a log except you may notice more wood density changes (depending on species) and glue-line ‘chatter’; not difficult but can feel almost like a loose crack once in a while until you get familiar. I use standard tools, 5/8” gouge is the most used - keep it sharp.
 
OK - thanks guys! Hopefully I'll get to the turning phase later this week. I've glued up several segmented bowls and they went together pretty fast. Doing one of these is a LOT slower, as the pieces are six-sided and can't easily be done quickly, so I'm adding 6-8 pieces a day, rubber banding and band clamping 'em together. Fun stuff!

Regards, Jim
 
Well, here it is nearly the middle of November and... the bowl I was working on got a catch and flew off the lathe. When it landed on the floor it decided to go back to its natural state - a bunch of pieces! Well, not completely, but most certainly not repairable. Great kindling, though. So, I created another one that made it all the way to completion, but I was not entirely happy with the results. As the author of the article mentioned, utmost accuracy in the angle and the side lengths are critical. Evidently I wasn't accurate enough, as I have a couple very tiny gaps between pieces. Plus, my board width wound up being a lot less than 1" and my bowl wound up being more like the size of a cup.

Anyway, I'm getting ready to try making version 3.0 but I do have a question for anyone who has actually read the article, and has even MADE one of these things. My question is in the calculation of how much lumber of each species is required. My high school math / geometry is 60+ years behind me so I really struggled trying to calculate my board lengths. This is based on having boards, when finished planed, that are 1" thick. I got my wife to draw it out for me in AugoCAD (she does this kind of thing every day) and it appears to me that each "slice" made on the saw at a 60-degree angle will eat up 3.72 inches of wood, plus 3/8" kerf width. That would come out to about 78". Is that reasonable? Is that what it took you to build one?
 
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