10% Wall on Rough Turn Sweet Gum

[Thomas Canfield]

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This shows a rough turned bowl blank after drying. It was 16 7/8" D x 1 3/4"WT x 7" D wet weighing 18.82# a couple of years ago. I got back to it and it was 17 1/8" to 15 3/4" oval OD and 15 3/4" to 12 3/8" oval ID weighing 11.01#. I mounted it between centers using expanded chuck inside and live center on tenon to round up the tenon and the lower portion of bowl. It did not warp uniformly and required removing more on one side than the other in addition to the oval. I used a wooden extension on my live center to keep pressure against the chuck when rounding up the bowl. I rounded it up to about 1" WT at first working both the inside and outside. The bowl would not hold round, and I kept working the outside some when working the inside after forming the rim and working the interion down to about 5/16" WT in 2" lengths. The top moved when going to lower levels, but did not create a large sanding problem. I did have to start with 80 grit instead of 120 but it went pretty fast all things considered.

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I used a jam chuck on inside and live center to turn down the tenon and checked to be sure bottom was recessed. The bottom sanded and the nub then cut off with flush cut saw using a piece of plastic to protect the bottom. The cut off nub was further removed with a chisel and final sanded. The 15 5/8" D x 6" H x 1/4" WT 2.98# bowl is currently in the finish process of tripoli buff and oil coats. I hope to post finished bowl in a couple of weeks.

[John Keeton]

Neat thread, Thomas!! That is a lot of distortion, and similar to what I experienced with the little cherry hollow form I just completed - though mine didn't move while turning. Your piece ended up making a really nice looking bowl, and I look forward to seeing the pics as finished.

[Tony Pridmore]

Hi Thomas,

Thanks for the in-progress photos. Looks like you're going to have a great finished bowl.

Did you have to start sanding at 80 grit because of tool marks due to the movement, or did you find the dried Gum had bad tearout when returning? I have turned a number of items from Sweet Gum. The wood was really solid when green. I rough turned bowls to 10% thickness and let 'em dry for a year. When turning the final shape I found the fibers tore out very easily even though I kept the gouge super sharp. I even tried spraying water and coating with shellac sanding sealer and paste wax. Nothing seemed to completely fix the issue. I haven't experienced any other wood that has done this after drying, at least not to this extent. Is it typical of Gum?

-Tony

[Bernie Weishapl]

Thomas thanks for sharing. I have had some of the same experience you have had with sweet gum and a couple of other woods. Thought maybe it was just me.

[Lee Koepke]

Nice! I missed out on some sweetgum on Thursday. They apparently dropped 3 trees from the office down the street, saw the trunks layin there at lunchtime ... called my buddies about an hour later, the tree guys already packed it all up and left !!!! All I wanted was a few bowl blanks out of it ....

[David E Keller]

That looks to be a great finished piece. I've not turned much sweet gum, but it's available around here. Is that coloring normal or is there some spalting going on?

[Thomas Canfield]

I had to start with 80 grit due to tool marks and the bowl warping during the turning. I did sharpen my tools more often to help prevent tearout, but some small ridges and tearout could not be corrected. The marbling look has been fairly consistent with the other Sweet Gum that I have turned and reflects the different grains and orientation in the wood. The Tripoli buff and oil finish seem to really bring out the wood character. There did not seem to be any spalting in the wood.

Centrifugal force on the 16 5/8" D with wall thickness from 1" to 1 3/4" allowed the bowl to warp when turning the inside. I tried to true up the outside after getting a uniform 1" wall at rim, but ran out of wood taking a light cut off the outside, inside, outside and inside and only in 2" segments to keep the side from being too flexible at final 5/16". The first large Sweet Gum bowl (19" D x 8" H) had a lot of the same warpage issues.

I would encourage anyone to get some Sweet Gum if they get a chance, but plan on some movement. I roughed some Cherry Laurel back in the summer, and the movement on that was even greater to the point that several rough hollow pieces & bowls could not be returned with the 10%+ wall.

[Baxter Smith]

Great looking bowl. I will have to try some!