Rung sizes for chair or stool

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Rung sizes for chair or stool

Postby Pcottingham » Sun Jul 19, 2015 8:43 pm

I am new to green woodworking, and I have read in many places that the best size for tenons for rungs or seat is 5/8". I have a 9/16" tenon former, and am wondering if that will be sufficient. I am mostly working in white oak, red oak, and maple.

I struggle to wrap my head around the belief that 1/16" in rived wood would make a whole lot of difference, but I'm brand new to this.

Any opinions?

Thanks.

Paul
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Re: Rung sizes for chair or stool

Postby benwillis » Tue Jul 21, 2015 2:47 pm

It's on the cusp of being too small I'd say - those joints are pretty essential stucturally in that kind of construction. You might just get away with it if you form the tenon once the wood's dry, but if you do it when it's green you'll lose c.10% more of that diameter through drying shrinkage, which probably would be too small. Though obviously if you form the tenon when it's dry you lose the ability to take advantage of the differential shrinkage you get with a tenon formed green and allowed to shrink to an oval that's slightly larger than the mortice, thus ensuring a tight fit without need for glue

Good luck

www.bw-greenwood.co.uk
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Re: Rung sizes for chair or stool

Postby Davie Crockett » Wed Jul 22, 2015 1:22 pm

I would echo what Ben says, You could also consider drying the ends of your tenons in hot sand prior to rounding them and then blind wedging them This would give you a super hygroscopic tenon which would actually expand at normal atmospheric humidity. The downsides of doing it this way is that you will have to be scrupulous about sand removal prior to using tools on it and you can only do one end at a time. You can heat the sand in a baking tray over a gas burner and it needs about 4 hours on a low setting with the tenons buried in it, stir it often and beware of "toasting" or over cooking the tenons as they will become hard but brittle.

PS, Where abouts are you pcottingham? There may be a group very close to you who can assist with loaning you a 5/8" tenon cutter....(Size does matter)
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Re: Rung sizes for chair or stool

Postby gavin » Mon Aug 03, 2015 7:30 am

Get Mike Abbott's Going with the Grain 2nd edition. You'll read there about using 5/8 cutter i.e. 15.62 mm tenon with a 14 mm mortice hole, and whittling the vertical faces of the tenon to 14 to 14.5 mm . The horizontal face will be whatevever it shrinks to from 15.62 mm - usually about 15 in the ash I use. All of this compresses into a glue-less joint.

As you lack a 5/8 cutter, just experiment with what you have.

Is your 9/16 inch former parallel-sided? or tapered?
If parrallel sided, I think it will be too weak for stool and chair construction.
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