Thursday, October 25, 2018

Guest blog bu Ty Stange: First Danish Chair Building Extravaganza

Thank you to Brian to let me post on his blog. This post is long overdue - life and business made sure I have been busy. Better late than newer - here goes:

This year I was given the honour to attend Danish Chair Building Extravaganza. Having newer met any of the attendants I did not know what to expect and what would be possible to make etc. On arrival I was greeted by Brian and Jonas in the yard and they were already in full action doing drawings, preparing tools etc. I felt welcome immediately and were given a workbench and a tour of Jonas impressive workshop and sawmill.

I brought several ideas for a project to build but, after seeing what the others were building, settled on a redesigned version of December Chair by Jasper Morrison & Wataru Kumano, produced by Nikkari Oy in Finland:
What I like, other than the sleek design, is that is has two special features. One is that the fabric that makes the seat is inset in a keyhole-shaped slot with a metal rod:

And also the back legs support the back rest in an interesting

Now just copying a design I feel is a bit like cheating. And this chair had a few shortcomings (probably due to the fact that is is made to be collapsible and flat pack):
- There is no support stopping the posts that hold the back rest from bending inwards. The frame is stiff enough not to break but not an optimal solution
- Only the seat is mounted in these nice slots, the back rest just threads over the posts.
Lets make that better!

Now, despite being a professional photographer, I am horrible at taking pictures in my free time. So this is a mixture of my own shop-notes-pictures and Brian´s

First a few, sketches to get the rough dimensions etc
Then a full size drawing

And ready to cut a lot of parts. Had brought some boards of hornbeam that I was fortunately enough to get from a park, Søndermarken, where I live in Copenhagen, then milled and stored for two years. Had only made small projects with it before and was curious to see how it behaved and looked. I wanted i light appearance and the hornbeam was perfect in that regard.
Hornbeam is very hard and i bit brittle so planing is a bit difficult. A bit like hard maple in that it is also diffuse-porous and super fine grained. Plane shavings look like fine lace.

While planing is difficult, turning, on the other hand, is super nice and an almost ivory like feel can be achieved. The only difficult part to turn is the back leg that needs two cylindrical and accurate parts with a straight taper in between, those needed a little extra care and frequent use of calipers.

To make the slots for the set and back rest to thread into I needed to make custom router bits, a 4 mm straight one and a 7 mm round keyhole shaped one. In my time working as a toolmaker a common type of bit for the metal mills was called a "stikkel", In english they appear to be called Single Flute Milling Cutters or D-bits.

For wood HSS steel is perfectly fine for smaller runs and the steel gets super sharp (in contrast to the usual carbide tipped bits) and Jonas had a few broken drill bits that I could use. The idea is that you take a round bar, grind away exactly half the diameter, shape the bit as desired and grind away a relief in order to establish a cutting edge. This is normally done in a specially made grinding machine with a support for the steel that can rotate in different directions. But a handheld grinding machine in a lathe works as well and
Jonas had a small hobby lathe (among several others) that I borrowed. Also found a grinding machine and here the result after a few hours of grinding away, simple and effective:
The bits got a bit blue after routing the grooves but HHS steel does not temper easily so it all worked well. The round back rest posts were routed in a v-groove support.

Jonas cozy workshop in morning light
Now next step was to drill the holes in the frame. I was so fortunate that Olav had this lovely old Arboga drill/mill machine that I could borrow. Jonas wrote a lot about that in his blog

Discussing details with Olav
Here all parts done, including the back rest support at left
And gluing it all up. It newer stops to amaze me how chair building is a lot of work on seemingly random parts, often for days - and suddenly it all just go together in a matter of minutes.

Olav had another gem as well, an old hand driven sewing machine that I borrowed. Perfect for the thick fabric (that I got from Jonas that had gotten it from a ship he worked on once)
Once I got the hang of it this machine worked like a charm, smooth and chewed through several layers of fabric. Perfect.
The length of the seat and back rest is quite critical. It needs to just exactly be able to thread into the holes  - and at the same time not be so loose that the seat meets the rails when sat on. Had to do a few test forth and back before it all worked.

The design calls for the edges of the fabric to be bent over and double at the sides. That way the diameter of the metal rod needs to be different in the ends. Found stainless steel rods at a local machinist Jonas sent me to. Made a small jig and ground away on Jonas bench grinder, rotating the rods with a handheld drill, worked just fine.

Sanded all surfaces til 400 grits and, after advice from Olav, polished the surface with plane shavings. That gave a lovely, smooth surface and decided to keep it like that. Had planned to use soap treatment and might do that if the polish does not last.

And then suddenly it was done. Jonas testing for comfort in a pile of planer shavings
At home in its final place. It sits on front of a broad bank of windows and wanted a piece that did not disturb the light from coming in. Think that works well.

Being part of DCBE was an honour, a pleasure and super fun. Being able to focus on only one thing for a whole week is such a luxury, thank you guys!

So that's it. Thank you for coming along, hope you enjoyed the read!


  1. Hi Ty

    Thanks for the very fine description of the build and the event.
    I am glad that you could make it to the event.

    I don't know why I look so gloomy on the picture testing out your chair, I guess it might still be after Brian smashing a window :-)

    Best regards

    1. I think that you look focused and like you are engaged in conversation (its my arm on the table saw)

      Glad to be part of it all!

  2. Thanks for the write-up, Ty! It was great to meet you and watch you build this chair. It turned out beautiful.

    1. A bit late but fun to write. Learned a lot from looking at you guys working - inspired to have a go at some sort of stick chair, time will teel what kind

  3. You should star selling tickets for the 'event'...
    Because you're getting seriouse chair built results!

    1. And you have to pay extra if you actually finish the chair in time!

  4. Great write up Ty, thanks for sharing. I am still curious about how on earth you fit those rod with the fabric wrap around inside those slots???
    Maybe obvious but it still eluded me :-)

    Thanks for hosting him Brian

    Bob, with Rudy back from outside, its cococococold...

  5. Thanks Robert!
    Difficult to write - easy to do. I´ll try:
    measured the thickness of the fabric (0,6mm as far as I remember) The circular part of the slot is Ø7 and the staright part is 4 mm. The edges of the fabric is double at the edges making it 1,2 mm thick there. A 5 mm rod fit perfesct as this makes for (0.6+0.6+5) 6,2 mm in all. Then there is 0.8 mm let for the whole thing to slode forth and back.
    In the ends the rods needed to accomodate for two layers og fabric making them ((1.2+1.2)-6,2)= 3.8mm thick.
    Then it was just making sure the ends of the seat/back rest was sewn at a perfect 90 degrees angle to the long side. Sewing one end with 3 rows and the other just a short stitch in prder to test and get the perfect legnt. Had to cut that up again and retry until the perfect length was reached.
    Then a bit of a fight getting one end in th eslot on one side and the other to, just barely, reach the slot in the other, moving in only a few mm in each side at each push.

    And thats it realy. Hope that made it clearer - else please ask again!