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Staked Stool - legs are splaying

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Forum topic by mmcc73 posted 07-30-2017 06:47 PM 1040 views 1 time favorited 33 replies Add to Favorites Watch
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mmcc73

29 posts in 468 days


07-30-2017 06:47 PM

Hi All – I’m working on a staked high stool from Chris Schwarz's plans.

The first instance I made from SPF from Home Depot. When I did a test sit on a smooth floor (prior to wedging the leg tenons, and prior to installing stretchers), the rear leg kicked out and snapped at the base of the tenon. I put it down to a poor wood choice and moved on to Mark 2.

For Mark 2, I’m using ash for the legs, and catalpa for the seat. I did install the stretchers and wedge the leg tenons. When sitting on it now, the legs don’t seem to be in danger of breaking but there was enough play that the stretchers came out of their mortises.

My workaround has been to bore the mortises in the legs and center stretcher all the way through, turn new stretchers with longer tenons, and wedge them into place. So far, it seems solid as a rock.

Any thoughts on why I was getting so much movement in the legs? This is my first foray into chair building, so I’m not sure what issues to look for. The mortises and tenons seemed like a good tight fit, and the movement seemed like the wood bending rather than a fault in the joints. Does the design just have too much angle in the rear leg?

I’m using a home-made reamer, made using a Harbor Freight compass saw blade for the cutter. I’m turning the tenons on my lathe.

Edit: here’s a picture from before wedging: http://i.imgur.com/PILZgD2.jpg


33 replies so far

View bondogaposis's profile

bondogaposis

4483 posts in 2191 days


#1 posted 07-30-2017 07:02 PM

Any thoughts on why I was getting so much movement in the legs?

Probably aren’t thick enough.

-- Bondo Gaposis

View Loren's profile

Loren

9643 posts in 3488 days


#2 posted 07-30-2017 07:08 PM

I haven’t used that style of joinery in chairs
I’ve made, but I’ve read articles on it. Some
of the finer points of doing these round
tenon joints are discussed in this book

One technique I’m aware of is using a
“shop oven” to dry out the tenoned parts
before cutting the tenons to fit. The moisture
content of the tenoned parts rises after
assembly and the joints snug up.

View Rick_M's profile (online now)

Rick_M

10646 posts in 2220 days


#3 posted 07-30-2017 07:18 PM

... the rear leg kicked out and snapped at the base of the tenon. I put it down to a poor wood choice and moved on to Mark 2.
- mmcc73

Could have been runout, an autopsy would confirm. Or it could be related to problem #2 …

Any thoughts on why I was getting so much movement in the legs?
- mmcc73

Tapers come loose when side pressure is applied, especially any kind of wiggle. It could happen if the legs are bowing but a 1” ash leg shouldn’t bow unless you are very heavy.(?) Are the stretchers rock solid? If not, it will allow the legs to move.

edit; Loren has a point about shrinkage. Was the ash kiln dried or air dry?

edit2; Schwarz knows this stool better than any of us, drop him an email. He’s been responsive in my experience.

-- http://thewoodknack.blogspot.com/

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mmcc73

29 posts in 468 days


#4 posted 07-30-2017 07:21 PM


Probably aren t thick enough.

- bondogaposis

I think you are on to something. I assumed that since he built his with Southern Yellow Pine, that ash would be overkill. However, according to this article SYP is actually stiffer than ash. It is much less hard, but actually stiffer than all of the hardwoods in the list except hickory and birch.

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Aj2

1179 posts in 1638 days


#5 posted 07-30-2017 07:54 PM

My guess is you Reamer is not producing a hole that matches your tenon.
I see wood that’s plenty thick but jointery that needs to be spot on.

-- Aj

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mmcc73

29 posts in 468 days


#6 posted 07-30-2017 08:46 PM



My guess is you Reamer is not producing a hole that matches your tenon.
I see wood that s plenty thick but jointery that needs to be spot on.

- Aj2

I’m not gonna defend my joinery skillz, but to my untrained eye they looked tight. That said, I think a commercial reamer and taper-er are in my future.

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mmcc73

29 posts in 468 days


#7 posted 07-30-2017 08:55 PM



Could have been runout, an autopsy would confirm. Or it could be related to problem #2 …

http://i.imgur.com/YdKYowP.jpg – I’m seeing long grain going all the way through the tenon, unless I’m not looking at it right.

Tapers come loose when side pressure is applied, especially any kind of wiggle. It could happen if the legs are bowing but a 1” ash leg shouldn t bow unless you are very heavy.(?) Are the stretchers rock solid? If not, it will allow the legs to move.

edit; Loren has a point about shrinkage. Was the ash kiln dried or air dry?

edit2; Schwarz knows this stool better than any of us, drop him an email. He s been responsive in my experience.

- Rick M

I’m about a 200 lb’er. Not light, but I would think not outside the design limits for the stool.

The ash was air dried, but the events in question happened pretty soon after assembly.

I’m not seeing how the stretchers (unless they were wedged from the outside, which mine now are) would keep the legs from splaying. They could pre-tension the legs, I suppose, which might keep them from moving more when force was applied.

Mr Schwarz does not have a public email address any longer – https://blog.lostartpress.com/2015/01/16/an-end-to-public-e-mail/ – and the blog post with the plans is closed for further comment.

View Aj2's profile

Aj2

1179 posts in 1638 days


#8 posted 07-30-2017 10:29 PM

I certainly wouldn’t blame you or your skills for a poor fit.I would blame that tool from Horror freight there’s nothing there that anyone of us really needs.I hate that place
If your reamed holes are not fuzzy inside maybe try coating the surface with a pencil.Then insert your tenon all the way.Pop it back out and look at the contact area.
Good luck

-- Aj

View Bluenote38's profile

Bluenote38

220 posts in 229 days


#9 posted 07-31-2017 10:34 AM

Really nice! I just finished one about 2 weeks ago and yours looks far better than mine (I see I have some work to do). I used a crappy knot ridden HD 2×12, hand formed tenons and augured holes but skipped the stretchers everything is super tight and no splaying (yet) My guess would be similar to AJ2. I will say that I drove my legs deeper. Almost all the way to the shoulder.

-- Bill - Rochester MI

View Dave Polaschek's profile

Dave Polaschek

1232 posts in 422 days


#10 posted 07-31-2017 12:10 PM

Choice of wood will definitely matter. On my first stool, I used some soft maple (was just marked “maple” at the lumber yard) for legs, and 1” legs with tenons tapering to 5/8 weren’t strong enough for my 280 pounds. I eventually ended up snapping a leg off.

Second go 'round, I used 2” red oak legs, with 1.5” straight tenons, staked into a much thicker seat. There was still some flex, and I ended up screwing the stretchers into the legs. Next time I’ll plan to stake the stretchers into the legs from the get-go.

I think The Schwarz’s design is good if everything is to tight tolerances, but any slop in your joinery (I know I had plenty in mine) will lead to movement, which can weaken the joints which will lead to more movement…

-- Dave - Minneapolis

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Bluenote38

220 posts in 229 days


#11 posted 07-31-2017 01:20 PM



5/8 weren t strong enough for my 280 pounds. I eventually ended up snapping a leg off.

- Dave Polaschek

Good point. I have to say that I probably wouldn’t have my 6’3” 280# son sit on the one I made – especially without stretchers wedged and glued in place.

-- Bill - Rochester MI

View rwe2156's profile

rwe2156

2719 posts in 1321 days


#12 posted 07-31-2017 01:30 PM

Or the tenons have shrunk a bit, or aren’t fitting tight enough.

Are you sure you’re tenons are super dry?

Aside from that the legs do look a bit spindly.

You could also pin the tenons from underneath.

-- Everything is a prototype thats why its one of a kind!!

View mmcc73's profile

mmcc73

29 posts in 468 days


#13 posted 07-31-2017 02:06 PM

So, when I made Mark 1 out of SPF, I actually made two of them (just like in Contact – why build one when you can have two at twice the price?) I’ve glued and wedged the legs, but not made stretchers. Right now it is relegated to outdoor usage, as the legs stick into the ground enough to prevent splay.

I’ll try to get some video of that one to see if we can’t diagnose what is going on.

View Manitario's profile

Manitario

2568 posts in 2723 days


#14 posted 07-31-2017 02:19 PM

I’m guessing that you don’t have a perfect match between the reamed holes on the seat and the taper of the tenon on the legs. Your seat looks thick enough, and I don’t think it has anything to do with your wood choices, ie. most of the staked stools have similar seat thickness. Having made a similar stool from Schwarz plans, I have zero play in the legs with my 200+lb weight but I used a matching Lee Valley reamer/taper to get a perfect fit.

-- Sometimes the creative process requires foul language. -- Charles Neil

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mmcc73

29 posts in 468 days


#15 posted 07-31-2017 02:28 PM



I have zero play in the legs with my 200+lb weight but I used a matching Lee Valley reamer/taper to get a perfect fit.
- Manitario

I was just looking at the Lee Valley web site. I was going to go with the Pro reamer. Which size tenon cutter did you get? I was thinking the 1/2”.

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