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Staked Stool - legs are splaying

by mmcc73
posted 07-30-2017 06:47 PM


33 replies so far

View bondogaposis's profile

bondogaposis

5371 posts in 2715 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

10477 posts in 4012 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 Woodknack's profile

Woodknack

12778 posts in 2744 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.

-- Rick M, http://thewoodknack.blogspot.com/

View mmcc73's profile

mmcc73

29 posts in 992 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.

View Aj2's profile

Aj2

2212 posts in 2162 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

View mmcc73's profile

mmcc73

29 posts in 992 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.

View mmcc73's profile

mmcc73

29 posts in 992 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

2212 posts in 2162 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 Bill Berklich's profile

Bill Berklich

761 posts in 753 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

3675 posts in 946 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

View Bill Berklich's profile

Bill Berklich

761 posts in 753 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 Robert's profile

Robert

3374 posts in 1845 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 992 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

2749 posts in 3247 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 992 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”.

View mmcc73's profile

mmcc73

29 posts in 992 days


#16 posted 08-01-2017 02:12 AM

I made a short video showing the flex, and ultimate destruction, of the SPF version of the stool: https://youtu.be/eNeneI0wiak

And I went ahead and got both the 1/2” and 5/8” versions of the tenon cutter. I don’t think my tenons caused the failure, but it should make creating them easier.

View Aj2's profile

Aj2

2212 posts in 2162 days


#17 posted 08-01-2017 03:11 AM

I watched your video and agree your tenons look good.Even if you used a wood with stiffer fibers I wouldn’t be without the stretchers.
Thanks for clearing up the confusion the Ash one looks great.

-- Aj

View Manitario's profile

Manitario

2749 posts in 3247 days


#18 posted 08-01-2017 04:13 AM


And I went ahead and got both the 1/2” and 5/8” versions of the tenon cutter. I don t think my tenons caused the failure, but it should make creating them easier.

- mmcc73

Nice! I just have the 5/8 version.

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

View Dave Polaschek's profile

Dave Polaschek

3675 posts in 946 days


#19 posted 08-01-2017 07:09 AM

I don’t think my tenons caused the failure, but it should make creating them easier.

Mine broke (with soft maple legs) almost exactly as yours did for the back leg. My thought was just that 5/8” tenons weren’t enough in weaker wood, which is why I did the followup with 1.5” tenons in red oak. I didn’t see any slop in the rear leg, but for the front two that failed when I hit the ground, it was hard to say for sure if my joints were good, as the elm seat also split on a line between the two front holes, and the legs snapped where the tenon entered the seat. Between better wood for the legs, much stouter tenons, screwed-in stretchers, and a thicker seat, there’s no movement in my mark 2 version.

-- Dave - Minneapolis

View mmcc73's profile

mmcc73

29 posts in 992 days


#20 posted 08-01-2017 12:48 PM



Even if you used a wood with stiffer fibers I wouldn t be without the stretchers.

OK – I have a very basic, foundational chair construction question… I assumed that stretchers were there primarily to resist compression, to “stretch” the legs apart. If their function is to resist tension – to prevent the legs from spreading – I would think that blind mortises would do a poor job of that. Without some mechanical mechanism to keep the stretcher in the mortise, like a wedge a screw or using wet/dry construction, it would seem that the chair staying together would depend completely on friction and/or glue between the mortise in the leg and the tenon of the stretcher.

So, a plain blind mortise, without some kind of mechanical reinforcement, seems like a bad design choice to me. Am I missing something? If the mortise and tenon are tight enough, will a plain blind mortise and tenon joint between a stretcher and leg hold for a long time?

View Aj2's profile

Aj2

2212 posts in 2162 days


#21 posted 08-01-2017 01:07 PM

I’m not sure what the cut off point would make a chair need a bigger thicker denser wood without the lower stretcher.
But I do know this if you can add a shoulder to the joint that will improve the strength also a square tenon is stronger too.
I’m not a engineer or a scientist just a common woodworker that uses his ordinary senses.:)

-- Aj

View Manitario's profile

Manitario

2749 posts in 3247 days


#22 posted 08-01-2017 04:08 PM

Schwarz has a number of posts dealing with whether chairs need stretchers or not, he also devotes some time in one of his books to this subject. Basically makes a pretty convincing argument that a well made chair, esp. in staked furniture doesn’t need stretchers for support. He also quotes a well known Windsor chair maker “I put stretchers on my chairs because the customer expects them, not because the chair (structurally) needs them”

I’ve only built one stool without stretchers, so it doesn’t really count as vast or definitive experience, but it is solid and the legs have no racking to them.

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

View Woodknack's profile

Woodknack

12778 posts in 2744 days


#23 posted 08-01-2017 06:40 PM


OK – I have a very basic, foundational chair construction question… I assumed that stretchers were there primarily to resist compression, to “stretch” the legs apart. If their function is to resist tension – to prevent the legs from spreading – I would think that blind mortises would do a poor job of that. Without some mechanical mechanism to keep the stretcher in the mortise, like a wedge a screw or using wet/dry construction, it would seem that the chair staying together would depend completely on friction and/or glue between the mortise in the leg and the tenon of the stretcher.

So, a plain blind mortise, without some kind of mechanical reinforcement, seems like a bad design choice to me. Am I missing something? If the mortise and tenon are tight enough, will a plain blind mortise and tenon joint between a stretcher and leg hold for a long time?

- mmcc73

Gravity is will try to push the legs outward, the stretchers will be in tension. The greater the angle or splay and the longer the legs, the more advantage your body will have in overcoming the legs. The smaller the tenons, the steeper the angle needs to be to resist your weight without breaking them, or the stronger the wood, or you can use stretchers to help distribute the weight and resist splaying. It’s not really a question of whether chairs can be built without stretchers, it’s just a matter of design. Any errors in fit of the joinery (not saying there were any) would aggravate things and make a failure more likely. I’m not very familiar with “staked” furniture but generally speaking tenon shoulders are structural and provide strength by resisting racking or sideways movement. Some people believe they are only there to cover the mortise and for looks but that isn’t true. But with these, getting a tight fit with the taper might outweigh the advantages of a shoulder, not sure. But if your tenons had a shoulder against the seat it would limit how far they could flex at the mortise.

-- Rick M, http://thewoodknack.blogspot.com/

View Bill Berklich's profile

Bill Berklich

761 posts in 753 days


#24 posted 08-02-2017 11:57 AM



I made a short video showing the flex, and ultimate destruction, of the SPF version of the stool: https://youtu.be/eNeneI0wiak

And I went ahead and got both the 1/2” and 5/8” versions of the tenon cutter. I don t think my tenons caused the failure, but it should make creating them easier.

- mmcc73

Hmmm… after seeing that video I may need to rethink using the one I made (out of HD 2×12)

-- Bill - Rochester MI

View Jeremymcon's profile

Jeremymcon

342 posts in 1044 days


#25 posted 08-02-2017 02:03 PM

Huh. I always thought that staked stool design looked a little spindly. I don’t recall whether Chris called for 5/8” tenons or 7/8”, but for a stool with such long legs, I’d probably be inclined to do 7/8”.

Im thinking your tenon probably matches your mortise pretty well, but to be certain you could make a matching tenon cutter. I posted mine as a project a while back:

http://lumberjocks.com/projects/322713

Just bore and ream a hole leaving a small area of flat 5/8 (or 7/8)” at the end (i.e don’t ream the whole way through). Then plane down until you just barely expose the edge of the mortise, and attach a jointer plane iron, making sure not to put the iron over the little flat at the end of the mortise. I’ve found its easiest to turn the tenon down to just under the diameter of the large end of the mortise before using the tenon cutter.

This style of tenon cutter is cheap, and there will be no question that your reamer and tenon cutters match each you made the tenon cutter with the reamer it is supposed to match!

As for spindles – the Windsor chair makers I’ve been reading about (my first ever chair is still in process, so take all of my advice with that in mind) go to great lengths to make sure that their stretchers fit tightly. Like, so tight that they can’t do a dry run. Some of them also shave little facets into the tenons to help the tenon compress and bind the mortise. They also tend to put the stretchers in compression – making them slightly longer than they actually need to be.

Wedging the back side of the tenon sounds like a good idea too, if you don’t mind the way that looks.

Good luck, and let us know what ends up working for you!

View mmcc73's profile

mmcc73

29 posts in 992 days


#26 posted 08-02-2017 02:23 PM

So I brought the “good” stool from my non-climate controlled, rather humid shop into the air conditioned comfort of my kitchen, and the wedged in stretchers starting slipping in their mortises (I hadn’t glued the tenons in the mortises, but had glued the wedges in the tenons. I assumed that would be sufficient). I attempted to drive further wedge material in there, we’ll see if they hold.

For the next go round, I’ll bake the stretchers in the oven before assembly.

View Jeremymcon's profile

Jeremymcon

342 posts in 1044 days


#27 posted 08-02-2017 02:38 PM

The tenons were slipping after you wedged them? That’s bizarre… My experience with tapeted tenons is that they’re hard to pull apart even without being wedged and glued. I made a practice joint with my reamer/tenon cutter and really hammered the leg in. I tried to remove it by pulling on it and broke the leg off before the (not glued/wedged) tenon came out. A hammer was the only thing that’d do it. Maybe the tenons aren’t fitting right after all… Or… Are you burnishing the tenons on the lathe at all? That’d probably make a difference – if they’re becoming at all burnished they probably won’t hold as well.

Chris makes it seem so simple to make… I’ve. Never tried it though but I guess it’s harder than it looks!

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mmcc73

29 posts in 992 days


#28 posted 08-02-2017 03:05 PM



The tenons were slipping after you wedged them? That s bizarre… My experience with tapeted tenons is that they re hard to pull apart even without being wedged and glued. I made a practice joint with my reamer/tenon cutter and really hammered the leg in. I tried to remove it by pulling on it and broke the leg off before the (not glued/wedged) tenon came out. A hammer was the only thing that d do it. Maybe the tenons aren t fitting right after all… Or… Are you burnishing the tenons on the lathe at all? That d probably make a difference – if they re becoming at all burnished they probably won t hold as well.

Chris makes it seem so simple to make… I ve. Never tried it though but I guess it s harder than it looks!

- Jeremymcon

Sorry, I wasn’t terribly clear above… the tenons going into the seat are still nice and tight. The tenons of the stretchers going into the legs, which are not tapered, started to slip.

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Jeremymcon

342 posts in 1044 days


#29 posted 08-02-2017 03:30 PM

Ah. That makes more sense. You did write “wedged-in stretchers” – I apparently wasn’t reading carefully.

I’d wager that putting the stretchers in compression by making them a hair longer than they need to be would stop them from slipping. Not sure if it’d fix the problem of the legs apparently being too weak to support a sitter though.

Some links regarding putting stretchers in compression:

http://www.windsorchairresources.com/tips/tenons.html (scroll down on the page to the “wet dry tenons” header)

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.wag-aic.org/2000/WAG_00_brandon.pdf&ved=0ahUKEwjogMSK7bjVAhXn64MKHWUHCxsQFgglMAA&usg=AFQjCNFPzDdPRaJXw4GCdpMVSOwx5uIW1A

Scroll down to the conclusion section.

Once again, good luck!

View shipwright's profile

shipwright

8293 posts in 3162 days


#30 posted 08-02-2017 10:57 PM

Interesting thread. I have had this stool for seven years (Black seat). The leg to seat and stretcher to leg joints are all bored (parallel sided) and do not penetrate through. All tenons have saw kerfs and little blind wedges in them and the stool is still as solid as a rock today. In fact I now have five of them that I use in my school and they are all absolutely sound.
Through penetrating the seat may serve some purpose but I would think through penetrating the stretchers would weaken them un-necessarily.
The photos in this build album will explain better. https://goo.gl/photos/sZUP8iiU3PcooUad9
If you look at the album please excuse the extreme detail. It was put together to help a beginner build one.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View mmcc73's profile

mmcc73

29 posts in 992 days


#31 posted 08-04-2017 02:58 PM


All tenons have saw kerfs and little blind wedges in them and the stool is still as solid as a rock today.
...
I would think through penetrating the stretchers would weaken them un-necessarily.

Interesting – I had read somewhere about that blind wedging technique (I think it was referred to as “fox wedging”) and was considering giving it a go. I had also read about back tapering, but was going to start another thread to inquire about that.

When you say “weaken them” are you referring to the legs being weakened because of the through hole?

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shipwright

8293 posts in 3162 days


#32 posted 08-04-2017 04:50 PM


.

When you say “weaken them” are you referring to the legs being weakened because of the through hole?

- mmcc73

Yes. The stretchers are quite thin and through holes would have to weaken them. The legs are somewhat thicker but still would IMHO be weakened more by through boring than by the method I used.
I can’t see the point, even in the seat, to through bore unless the seat is too thin to give sufficient seat to the tenons.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View mmcc73's profile

mmcc73

29 posts in 992 days


#33 posted 08-07-2017 05:40 PM

On the most recent one, I tried the hidden wedges. I also used the Lee Valley reamer and tenon cutter, which has a larger included angle than my shop made ones. So, even before installing the stretchers, the legs were more solid due to the tenon being thicker. The stretchers seem to be holding just fine. I think that is what I will do the next time as well.

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