Post and rung chairs, a question

[paul cottingham]

Anyone here who has made a post and rung chair, (or anyone with some knowledge of strength of joints) I have a quick question about tenon cutters. I'm consider a powered tenon cutter for rounding the ends of the rungs. LV sells 2 I think will fill the bill. One is The mini tenon cutter
http://www.leevalley.com/en/garden/p...,33286&p=44248
Which makes a 9/16" tenon, the other is the Power tenon cutter
http://www.leevalley.com/en/wood/pag...,42299&p=42299
Which makes a 5/8" tenon.

my question is this. Do you think a 9/16" tenon will be strong enough? Each chair or stool will have 8 rungs, 1 for the middle of the leg, the other for the seat, on all 4 sides. I think if I use nice, rived, straight grain wood, 9/16" should be sufficient. I am willing (reluctantly, as cash is tight, and this is being funded by a generous friend in exchange for computer help) to use a 5/8" tenon if it will be significantly stronger.

any ideas? Am I worried about nothing? It is only 1/16" difference after all.

thanks in advance, as always.

[Sean Hughto]

Make yourself a 5/16ths dowel the length of the members from the same wood you intend to use and try to break it. I'm guessing you will conclude that it is plenty strong.

[Jim Koepke]

One of these would be cheaper and then you wouldn't be committed to a single size:

Hollow Auger & Depth Scale.jpg

For one of these you might want to make it a little over size and then trim it by hand.

jtk

[Mike Holbrook]

I would go by someones plans who has built lots of a particular chair design and refined it like Drew Langsner "The Chairmaker's Workshop". I believe Drew still sells plans and full size patterns for 12 different chairs that have been made in his classes for many years.

I have the LV hand tenon cutter and reamer which we used in a Chris Schwarz class to make sawbenches. They work fairly well if they are very sharp, not so well if not so sharp. The easiest way to make tenons in my experience is with a lathe.

[paul cottingham]

One of these would be cheaper and then you wouldn't be committed to a single size:

Hollow Auger & Depth Scale.jpg

For one of these you might want to make it a little over size and then trim it by hand.

jtk

Jim, I would love one of those, but have been unable to find one at a price I can afford. They are indeed slick.

[paul cottingham]

I would go by someones plans who has built lots of a particular chair design and refined it like Drew Langsner "The Chairmaker's Workshop". I believe Drew still sells plans and full size patterns for 12 different chairs that have been made in his classes for many years.

I have the LV hand tenon cutter and reamer which we used in a Chris Schwarz class to make sawbenches. They work fairly well if they are very sharp, not so well if not so sharp. The easiest way to make tenons in my experience is with a lathe.

I have one of Langsners books (chair makers workshop) a copy of Jenny (John) Alexander's book and video and several other chair making books. Langsner recommends a 5/8" tenon, (I think, he is somewhat difficult to pin down) as does Alexander, (again, sort of.) but I find myself wondering if that is for strength reasons, or because that was the prevailing tool size at the time they got their start. I honestly struggle to believe that 1/16" makes a structural difference, especially when a chair usually has 3 rungs per side. 12 rungs! 12!

But maybe I'm missing something.

[David Keller NC]

This probably goes without saying, but I'm thinking the answer is "it depends". Specifically, what type of wood (maple, poplar, oak, etc...), the quality of construction (you've already mentioned riving, another thought is whether the rungs will be "pinned"), and importantly, the size of the persons using the chair. A chair for a 110 lb. woman is probably going to be completely unbreakable with 3/8" tenons, while a 320 lb, 6'-4" man is probably going to have issues with the 5/8" tenons.