A while back I showed a small sample of how the Legacy Ornamental Mill works with a small spiral cane.
Turning those little things is a pure pleasure and I do it often.
But sometimes the demand is for a large spiral column.
This mill, model 1500EX is a long bed machine, signified by the EX in the model number. So I made the columns outside the front entry to our house/knit shop.
But there is an inherent problem with large, solid columns.
They split.
No matter what material is used (plastic excepted), it splits.
The process goes this way:
As the outer parts of the column dry out they contract.
Not much, but it doesn’t take much.
The inner core doesn’t contract at the same rate.
So the outer layers are now too small to cover the inner, unshrunken core.
Result?
Cracks.
Just look at the logs in a log house. Most of them split.
Most commercial columns are hollow, preventing the problem.
My columns are hollow, too.
Here’s how I do it.
I accentuated the lines showing the birdsmouth cuts that join the pieces in a six sided hollow form
Blocks are fitted to the column to fasten it in the mill. Then the form is milled round, first, and then the detail is milled in.
Here’s a short practice piece that didn’t have the birdsmouth joints, but does show the spiral forms.
The actual columns were finished outside with good primer and exterior gloss enamel. Then I filled the inside with foam to prevent moisture and insects from coming in.
Best regards,
d
-- If a man says something in the forest and there's no woman to hear it, is he still wrong?
10 comments so far
papadan
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483 posts in 268 days
posted 51 days ago
Good information Don, you got my porch columns done yet? LOL
-- Dan-- Info for all @ http://www.hoistman.com
a1Jim
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17211 posts in 477 days
posted 51 days ago
Interesting blog
-- Jim from Heirloom Woodshop, custom furniture ,maker, woodworking school, heirloomwoodshop.com
Don "Dances with Wood" Butler
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281 posts in 295 days
posted 51 days ago
Dan,
I don’t recall that order. When did you send it?
LOL
d
-- If a man says something in the forest and there's no woman to hear it, is he still wrong?
Mark Shymanski
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1555 posts in 612 days
posted 51 days ago
Very interesting, thank you.
-- ...it's rennovation time!!!
Loucarb
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962 posts in 345 days
posted 51 days ago
Thanks for sharing that is very interesting.
DAN
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6468 posts in 883 days
posted 51 days ago
Good one Don! that mill sounds like a cool toy…
-- work from your heart and your spirit will live forever
DaveR
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1529 posts in 620 days
posted 51 days ago
Good work, Don.
The birdsmouth method is an excellent one for making hollow turnings. In addition to the benefits you mention as far as checking and cracking, a hollow column can be nearly as strong as a solid one. The birdsmouth method makes it very easy to create tapered columns and you don’t have to make them round, either. There’s a fellow out east someplace who makes looms for oars and shafts for canoe paddles using the birdsmouth technique. He makes oval-sectioned shafts so you have a better grip when paddling.
I turned a couple of birdsmouth spars when I had my Legacy. I had to modify the machine to handle the length but I got the job done. Very light and stiff when they got finished.
Someplace I have an Excel-based calculator for designing them.
-- Until you spread your wings, you'll have no idea how far you can walk.
cabinetmaster
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8749 posts in 458 days
posted 51 days ago
Wow. Just when I need to do a 9” X 52” hollow column, someone makes a post. I like that Idea. It sure would save on a major glue-up. Plus I have to split it to go around a 4 X 4 post. I hope you don’t mind me using this idea.
-- Jerry--A man can never have enough tools or clamps
Don "Dances with Wood" Butler
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281 posts in 295 days
posted 51 days ago
Not at all.
Please do.
-- If a man says something in the forest and there's no woman to hear it, is he still wrong?
DaveR
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1529 posts in 620 days
posted 51 days ago
Jerry, I’m sure you can see that when you glue up the column, you omit the glue in the birdsmoths 180° apart and the column can be split. You’ll have a good time with this.
-- Until you spread your wings, you'll have no idea how far you can walk.