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Need some advice with hollow form issue.

Grey Darrah

Grey Darrah

Joined
May 6, 2018
Messages
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Location
Cartersville, GA
I'm working on an end grain piece of maple that I'm planning on shaping into a heart-ish/baloon form. It's green wood and I'm turning it to finished dimensions (about 3/16ths thick) while wet. It's about 12 inches tall (plus a tenon) and about 10 inches wide near the top. I'll be using a steady rest for the hollowing.

My issue is wanting the get the base as narrow as possible, before I start hollowing. Because I'm going to finish it while wet, it's going to be out of round by the time I get it hollowed out. I think this means that I can't go back, after it's hollowed and make the base above the tenon more narrow, because the piece will likely no longer be perfectly round and I may not have enough thickness in the walls to take it back to round.

I've attached a rough drawing of the HF below. What I'm wondering, is how narrow can I get the area above the tenon (at my red lines) while keeping enough stability in the piece to hollow without getting into significant vibration, or worse, having it snap off above the tenon? The tenon itself is 3.5 inches in diameter. Do you think I could take that base area above the tenon down to a 2 inch diameter...what about 1.5 inches?

Thanks for any help,
Grey
greys-hf.jpg
 
there are others who are more knowledgeable....but here goes....the area 5 or 6 inches above the tendon you hollow before you turn the outside....Larry Hasiak..is the Turner I watched do rotation called Hollowing the low tech way
 
Grey,

The key is to turn the outside and inside rather simultaneously.
  1. Turn the whole form round, but leave a lot of wood at the bottom (next the headstock).
  2. Shape the outside about ⅓ of the way down, then hollow this out
  3. Shape the next ⅓ down, and hollow this out. Be sure to leave the first ⅓ alone : it’s too fragile.
  4. For the last ⅓, consider reverse the process. Hollow the inside, and the tackle the outside.
The extra wood retained as long as possible helps support the top.

I think Lyle Jameson discussed this at the 2017 or 2016 AAW symposium.

Kind regards,
Rich
 
I would do it like Rich and John said leave the base thick.
I might not use a steady for a piece this size. If it is nice cutting maple
I would not expect to much vibration with a 6-8” base.
I might also remove the extra wood in 1.5” steps instead of 1” steps.

E5390A10-0356-4F7C-8897-83660726AC6B.jpeg
 
One aspect of this form is that if the wall thickness is uniform to the narrow foot, it will be very prone to tipping.
I have several around the house that must be secured with museum wax/stickum to keep them upright.
The ones with a small base that are stable have a thicker wall towards the bottom.
Green wood and variable wall thickness are a recipe for cracking so they have to be carefully dried.
When you have the piece reversed to finish the bottom you should be able to complete some careful final shaping of the lower profile.
 
I really appreciate all the help/suggestions. As recommended by many, I ended up leaving the last few inches (near the tenon) thicker on the outside, then hollowing down to that area. For finishing the base inside and out, instead of taking it an inch or so at a time from outside to inside, I just finished the outside base area in one whack, then hollowed those last few inches.

I still wonder how it would have come out if I'd have shaped the base down to the final 2 inch diameter above my tenon before starting the hollowing.

Now I just need to reverse turn the tenon off and let it dry. Thanks again for the help from everyone.

Grey

IMG_20181001_220220-01.jpeg
 
It seems like a nice job on the turning and hollowing.

But the one thing that makes me nervous is the small diameter foot compared to the upper mass of the piece. Seems like you might have to use museum was or similar to keep it from tipping if it was put to use like for dried flowers, etc.

I wonder if there are any "rules" or recommendations for foot diameter with respect to height and upper diameter of turnings.

My wife has a collection of similarly small footed blown glass that worries us when the grand kids come thundering through our house.
 
I always worry about pieces that have small bottoms. Eric Loffstrom came up with an idea for his Rain Drop sculptures. He puts a small rare earth magnet in the bottom of the piece, and a small metal plate for the magnet to grab onto. For me, if I even walked into the same room with a piece like that, I am sure it would fall over if I even got close to it.... Nice piece.

robo hippy
 
Doug Rasmussen said:
But the one thing that makes me nervous is the small diameter foot compared to the upper mass of the piece. Seems like you might have to use museum was or similar to keep it from tipping if it was put to use like for dried flowers, etc.
Click to expand...

One option is to add a base, of glass.
I've had glass cut, 1/2" to 3/4" thick, in an appropriate diameter.
Then glue that to the vase as a base.

Its wider, adds weight, but doesn't visually distract.

I've also tried stone bases. Soap stone cuts and polishes easily. Granite is a bit more of a challenge.
Leave a tenon on the vase, and cut an insert into the stone. Epoxy them together
 
Grey,

You could also consider making a stand to hold the object. Maybe a metal ring ⅓ up the side, with steel or aluminum legs.

With such an addition, you could even take the object down to a point.

Rich
 
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